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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html>
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<html xmlns="http://www.w3.org/1999/xhtml">
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  <body>
    <h1>Domain XML format</h1>

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    <ul id="toc"></ul>

    <p>
      This section describes the XML format used to represent domains, there are
      variations on the format based on the kind of domains run and the options
      used to launch them. For hypervisor specific details consult the
      <a href="drivers.html">driver docs</a>
    </p>


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    <h2><a id="elements">Element and attribute overview</a></h2>
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    <p>
      The root element required for all virtual machines is
      named <code>domain</code>. It has two attributes, the
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      <a id="attributeDomainType"><code>type</code></a>
      specifies the hypervisor used for running
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      the domain. The allowed values are driver specific, but
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      include "xen", "kvm", "qemu" and "lxc". The
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      second attribute is <code>id</code> which is a unique
      integer identifier for the running guest machine. Inactive
      machines have no id value.
    </p>


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    <h3><a id="elementsMetadata">General metadata</a></h3>
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<pre>
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&lt;domain type='kvm' id='1'&gt;
  &lt;name&gt;MyGuest&lt;/name&gt;
  &lt;uuid&gt;4dea22b3-1d52-d8f3-2516-782e98ab3fa0&lt;/uuid&gt;
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  &lt;genid&gt;43dc0cf8-809b-4adb-9bea-a9abb5f3d90e&lt;/genid&gt;
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  &lt;title&gt;A short description - title - of the domain&lt;/title&gt;
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  &lt;description&gt;Some human readable description&lt;/description&gt;
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  &lt;metadata&gt;
    &lt;app1:foo xmlns:app1="http://app1.org/app1/"&gt;..&lt;/app1:foo&gt;
    &lt;app2:bar xmlns:app2="http://app1.org/app2/"&gt;..&lt;/app2:bar&gt;
  &lt;/metadata&gt;
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  ...</pre>
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    <dl>
      <dt><code>name</code></dt>
      <dd>The content of the <code>name</code> element provides
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        a short name for the virtual machine. This name should
        consist only of alpha-numeric characters and is required
        to be unique within the scope of a single host. It is
        often used to form the filename for storing the persistent
        configuration file. <span class="since">Since 0.0.1</span></dd>
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      <dt><code>uuid</code></dt>
      <dd>The content of the <code>uuid</code> element provides
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        a globally unique identifier for the virtual machine.
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        The format must be RFC 4122 compliant,
        eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
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        If omitted when defining/creating a new machine, a random
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        UUID is generated. It is also possible to provide the UUID
        via a <a href="#elementsSysinfo"><code>sysinfo</code></a>
        specification. <span class="since">Since 0.0.1, sysinfo
        since 0.8.7</span></dd>
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      <dt><code>genid</code></dt>
      <dd><span class="since">Since 4.4.0</span>, the <code>genid</code>
        element can be used to add a Virtual Machine Generation ID which
        exposes a 128-bit, cryptographically random, integer value identifier,
        referred to as a Globally Unique Identifier (GUID) using the same
        format as the <code>uuid</code>. The value is used to help notify
        the guest operating system when the virtual machine is re-executing
        something that has already executed before, such as:

        <ul>
          <li>VM starts executing a snapshot</li>
          <li>VM is recovered from backup</li>
          <li>VM is failover in a disaster recovery environment</li>
          <li>VM is imported, copied, or cloned</li>
        </ul>

        The guest operating system notices the change and is then able to
        react as appropriate by marking its copies of distributed databases
        as dirty, re-initializing its random number generator, etc.

        <p>
        The libvirt XML parser will accept both a provided GUID value
        or just &lt;genid/&gt; in which case a GUID will be generated
        and saved in the XML. For the transitions such as above, libvirt
        will change the GUID before re-executing.</p></dd>

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      <dt><code>title</code></dt>
      <dd>The optional element <code>title</code> provides space for a
        short description of the domain. The title should not contain
        any newlines. <span class="since">Since 0.9.10</span>.</dd>

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      <dt><code>description</code></dt>
      <dd>The content of the <code>description</code> element provides a
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        human readable description of the virtual machine. This data is not
        used by libvirt in any way, it can contain any information the user
        wants. <span class="since">Since 0.7.2</span></dd>

      <dt><code>metadata</code></dt>
      <dd>The <code>metadata</code> node can be used by applications
        to store custom metadata in the form of XML
        nodes/trees. Applications must use custom namespaces on their
        XML nodes/trees, with only one top-level element per namespace
        (if the application needs structure, they should have
        sub-elements to their namespace
        element). <span class="since">Since 0.9.10</span></dd>
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   </dl>
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    <h3><a id="elementsOS">Operating system booting</a></h3>
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    <p>
      There are a number of different ways to boot virtual machines
      each with their own pros and cons.
    </p>

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    <h4><a id="elementsOSBIOS">BIOS bootloader</a></h4>
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    <p>
      Booting via the BIOS is available for hypervisors supporting
      full virtualization. In this case the BIOS has a boot order
      priority (floppy, harddisk, cdrom, network) determining where
      to obtain/find the boot image.
    </p>

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<pre>
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...
&lt;os&gt;
  &lt;type&gt;hvm&lt;/type&gt;
  &lt;loader readonly='yes' secure='no' type='rom'&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
  &lt;nvram template='/usr/share/OVMF/OVMF_VARS.fd'&gt;/var/lib/libvirt/nvram/guest_VARS.fd&lt;/nvram&gt;
  &lt;boot dev='hd'/&gt;
  &lt;boot dev='cdrom'/&gt;
  &lt;bootmenu enable='yes' timeout='3000'/&gt;
  &lt;smbios mode='sysinfo'/&gt;
  &lt;bios useserial='yes' rebootTimeout='0'/&gt;
&lt;/os&gt;
...</pre>
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    <dl>
      <dt><code>type</code></dt>
      <dd>The content of the <code>type</code> element specifies the
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        type of operating system to be booted in the virtual machine.
        <code>hvm</code> indicates that the OS is one designed to run
        on bare metal, so requires full virtualization. <code>linux</code>
        (badly named!) refers to an OS that supports the Xen 3 hypervisor
        guest ABI. There are also two optional attributes, <code>arch</code>
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        specifying the CPU architecture to virtualization,
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        and <a id="attributeOSTypeMachine"><code>machine</code></a> referring
        to the machine type. The <a href="formatcaps.html">Capabilities XML</a>
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        provides details on allowed values for
        these. <span class="since">Since 0.0.1</span></dd>
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      <dt><a id="elementLoader"><code>loader</code></a></dt>
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      <dd>The optional <code>loader</code> tag refers to a firmware blob,
        which is specified by absolute path,
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        used to assist the domain creation process. It is used by Xen
        fully virtualized domains as well as setting the QEMU BIOS file
        path for QEMU/KVM domains. <span class="since">Xen since 0.1.0,
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        QEMU/KVM since 0.9.12</span> Then, <span class="since">since
        1.2.8</span> it's possible for the element to have two
        optional attributes: <code>readonly</code> (accepted values are
        <code>yes</code> and <code>no</code>) to reflect the fact that the
        image should be writable or read-only. The second attribute
        <code>type</code> accepts values <code>rom</code> and
        <code>pflash</code>. It tells the hypervisor where in the guest
        memory the file should be mapped.  For instance, if the loader
        path points to an UEFI image, <code>type</code> should be
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        <code>pflash</code>. Moreover, some firmwares may
        implement the Secure boot feature. Attribute
        <code>secure</code> can be used then to control it.
        <span class="since">Since 2.1.0</span></dd>
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      <dt><code>nvram</code></dt>
      <dd>Some UEFI firmwares may want to use a non-volatile memory to store
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        some variables. In the host, this is represented as a file and the
        absolute path to the file is stored in this element. Moreover, when the
        domain is started up libvirt copies so called master NVRAM store file
        defined in <code>qemu.conf</code>. If needed, the <code>template</code>
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        attribute can be used to per domain override map of master NVRAM stores
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        from the config file. Note, that for transient domains if the NVRAM file
        has been created by libvirt it is left behind and it is management
        application's responsibility to save and remove file (if needed to be
        persistent). <span class="since">Since 1.2.8</span></dd>
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      <dt><code>boot</code></dt>
      <dd>The <code>dev</code> attribute takes one of the values "fd", "hd",
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        "cdrom" or "network" and is used to specify the next boot device
        to consider. The <code>boot</code> element can be repeated multiple
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        times to setup a priority list of boot devices to try in turn.
        Multiple devices of the same type are sorted according to their
        targets while preserving the order of buses. After defining the
        domain, its XML configuration returned by libvirt (through
        virDomainGetXMLDesc) lists devices in the sorted order. Once sorted,
        the first device is marked as bootable. Thus, e.g., a domain
        configured to boot from "hd" with vdb, hda, vda, and hdc disks
        assigned to it will boot from vda (the sorted list is vda, vdb, hda,
        hdc). Similar domain with hdc, vda, vdb, and hda disks will boot from
        hda (sorted disks are: hda, hdc, vda, vdb). It can be tricky to
        configure in the desired way, which is why per-device boot elements
        (see <a href="#elementsDisks">disks</a>,
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        <a href="#elementsNICS">network interfaces</a>, and
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        <a href="#elementsHostDev">USB and PCI devices</a> sections below) were
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        introduced and they are the preferred way providing full control over
        booting order. The <code>boot</code> element and per-device boot
        elements are mutually exclusive. <span class="since">Since 0.1.3,
        per-device boot since 0.8.8</span>
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      </dd>
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      <dt><code>smbios</code></dt>
      <dd>How to populate SMBIOS information visible in the guest.
        The <code>mode</code> attribute must be specified, and is either
        "emulate" (let the hypervisor generate all values), "host" (copy
        all of Block 0 and Block 1, except for the UUID, from the host's
        SMBIOS values;
        the <a href="html/libvirt-libvirt-host.html#virConnectGetSysinfo">
        <code>virConnectGetSysinfo</code></a> call can be
        used to see what values are copied), or "sysinfo" (use the values in
        the <a href="#elementsSysinfo">sysinfo</a> element).  If not
        specified, the hypervisor default is used. <span class="since">
        Since 0.8.7</span>
      </dd>
  </dl>
      <p>Up till here the BIOS/UEFI configuration knobs are generic enough to
      be implemented by majority (if not all) firmwares out there. However,
      from now on not every single setting makes sense to all firmwares. For
      instance, <code>rebootTimeout</code> doesn't make sense for UEFI,
      <code>useserial</code> might not be usable with a BIOS firmware that
      doesn't produce any output onto serial line, etc. Moreover, firmwares
      don't usually export their capabilities for libvirt (or users) to check.
      And the set of their capabilities can change with every new release.
      Hence users are advised to try the settings they use before relying on
      them in production.</p>
  <dl>
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      <dt><code>bootmenu</code></dt>
      <dd> Whether or not to enable an interactive boot menu prompt on guest
      startup. The <code>enable</code> attribute can be either "yes" or "no".
      If not specified, the hypervisor default is used. <span class="since">
      Since 0.8.3</span>
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      Additional attribute <code>timeout</code> takes the number of milliseconds
      the boot menu should wait until it times out.  Allowed values are numbers
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      in range [0, 65535] inclusive and it is ignored unless <code>enable</code>
      is set to "yes". <span class="since">Since 1.2.8</span>
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      </dd>
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      <dt><code>bios</code></dt>
      <dd>This element has attribute <code>useserial</code> with possible
        values <code>yes</code> or <code>no</code>. It enables or disables
        Serial Graphics Adapter which allows users to see BIOS messages
        on a serial port. Therefore, one needs to have
        <a href="#elementCharSerial">serial port</a> defined.
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        <span class="since">Since 0.9.4</span>.
        <span class="since">Since 0.10.2 (QEMU only)</span> there is
        another attribute, <code>rebootTimeout</code> that controls
        whether and after how long the guest should start booting
        again in case the boot fails (according to BIOS). The value is
        in milliseconds with maximum of <code>65535</code> and special
        value <code>-1</code> disables the reboot.
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      </dd>
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    </dl>

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    <h4><a id="elementsOSBootloader">Host bootloader</a></h4>
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    <p>
      Hypervisors employing paravirtualization do not usually emulate
      a BIOS, and instead the host is responsible to kicking off the
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      operating system boot. This may use a pseudo-bootloader in the
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      host to provide an interface to choose a kernel for the guest.
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      An example is <code>pygrub</code> with Xen. The Bhyve hypervisor
      also uses a host bootloader, either <code>bhyveload</code> or
      <code>grub-bhyve</code>.
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    </p>

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<pre>
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...
&lt;bootloader&gt;/usr/bin/pygrub&lt;/bootloader&gt;
&lt;bootloader_args&gt;--append single&lt;/bootloader_args&gt;
...</pre>
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    <dl>
      <dt><code>bootloader</code></dt>
      <dd>The content of the <code>bootloader</code> element provides
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        a fully qualified path to the bootloader executable in the
        host OS. This bootloader will be run to choose which kernel
        to boot. The required output of the bootloader is dependent
        on the hypervisor in use. <span class="since">Since 0.1.0</span></dd>
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      <dt><code>bootloader_args</code></dt>
      <dd>The optional <code>bootloader_args</code> element allows
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        command line arguments to be passed to the bootloader.
        <span class="since">Since 0.2.3</span>
        </dd>
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    </dl>

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    <h4><a id="elementsOSKernel">Direct kernel boot</a></h4>
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    <p>
      When installing a new guest OS it is often useful to boot directly
      from a kernel and initrd stored in the host OS, allowing command
      line arguments to be passed directly to the installer. This capability
      is usually available for both para and full virtualized guests.
    </p>

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<pre>
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...
&lt;os&gt;
  &lt;type&gt;hvm&lt;/type&gt;
  &lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
  &lt;kernel&gt;/root/f8-i386-vmlinuz&lt;/kernel&gt;
  &lt;initrd&gt;/root/f8-i386-initrd&lt;/initrd&gt;
  &lt;cmdline&gt;console=ttyS0 ks=http://example.com/f8-i386/os/&lt;/cmdline&gt;
  &lt;dtb&gt;/root/ppc.dtb&lt;/dtb&gt;
  &lt;acpi&gt;
    &lt;table type='slic'&gt;/path/to/slic.dat&lt;/table&gt;
  &lt;/acpi&gt;
&lt;/os&gt;
...</pre>
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    <dl>
      <dt><code>type</code></dt>
      <dd>This element has the same semantics as described earlier in the
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        <a href="#elementsOSBIOS">BIOS boot section</a></dd>
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      <dt><code>loader</code></dt>
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      <dd>This element has the same semantics as described earlier in the
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        <a href="#elementsOSBIOS">BIOS boot section</a></dd>
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      <dt><code>kernel</code></dt>
      <dd>The contents of this element specify the fully-qualified path
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        to the kernel image in the host OS.</dd>
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      <dt><code>initrd</code></dt>
      <dd>The contents of this element specify the fully-qualified path
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        to the (optional) ramdisk image in the host OS.</dd>
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      <dt><code>cmdline</code></dt>
      <dd>The contents of this element specify arguments to be passed to
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        the kernel (or installer) at boot time. This is often used to
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        specify an alternate primary console (eg serial port), or the
        installation media source / kickstart file</dd>
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      <dt><code>dtb</code></dt>
      <dd>The contents of this element specify the fully-qualified path
        to the (optional) device tree binary (dtb) image in the host OS.
        <span class="since">Since 1.0.4</span></dd>
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      <dt><code>acpi</code></dt>
      <dd>The <code>table</code> element contains a fully-qualified path
        to the ACPI table. The <code>type</code> attribute contains the
        ACPI table type (currently only <code>slic</code> is supported)
        <span class="since">Since 1.3.5 (QEMU only)</span></dd>
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    </dl>

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    <h4><a id="elementsOSContainer">Container boot</a></h4>
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    <p>
      When booting a domain using container based virtualization, instead
      of a kernel / boot image, a path to the init binary is required, using
      the <code>init</code> element. By default this will be launched with
      no arguments. To specify the initial argv, use the <code>initarg</code>
      element, repeated as many time as is required. The <code>cmdline</code>
      element, if set will be used to provide an equivalent to <code>/proc/cmdline</code>
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      but will not affect init argv.
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    </p>
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    <p>
      To set environment variables, use the <code>initenv</code> element, one
      for each variable.
    </p>
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    <p>
      To set a custom work directory for the init, use the <code>initdir</code>
      element.
    </p>
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    <p>
      To run the init command as a given user or group, use the <code>inituser</code>
      or <code>initgroup</code> elements respectively. Both elements can be provided
      either a user (resp. group) id or a name. Prefixing the user or group id with
      a <code>+</code> will force it to be considered like a numeric value. Without
      this, it will be first tried as a user or group name.
    </p>
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    <pre>
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&lt;os&gt;
  &lt;type arch='x86_64'&gt;exe&lt;/type&gt;
  &lt;init&gt;/bin/systemd&lt;/init&gt;
  &lt;initarg&gt;--unit&lt;/initarg&gt;
  &lt;initarg&gt;emergency.service&lt;/initarg&gt;
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  &lt;initenv name='MYENV'&gt;some value&lt;/initenv&gt;
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  &lt;initdir&gt;/my/custom/cwd&lt;/initdir&gt;
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  &lt;inituser&gt;tester&lt;/inituser&gt;
  &lt;initgroup&gt;1000&lt;/initgroup&gt;
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&lt;/os&gt;
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    </pre>


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    <p>
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      If you want to enable user namespace, set the <code>idmap</code> element.
      The <code>uid</code> and <code>gid</code> elements have three attributes:
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    </p>

    <dl>
      <dt><code>start</code></dt>
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      <dd>First user ID in container. It must be '0'.</dd>
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      <dt><code>target</code></dt>
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      <dd>The first user ID in container will be mapped to this target user
          ID in host.</dd>
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      <dt><code>count</code></dt>
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      <dd>How many users in container are allowed to map to host's user.</dd>
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    </dl>

    <pre>
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&lt;idmap&gt;
  &lt;uid start='0' target='1000' count='10'/&gt;
  &lt;gid start='0' target='1000' count='10'/&gt;
&lt;/idmap&gt;
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    </pre>


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    <h3><a id="elementsSysinfo">SMBIOS System Information</a></h3>
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    <p>
      Some hypervisors allow control over what system information is
      presented to the guest (for example, SMBIOS fields can be
      populated by a hypervisor and inspected via
      the <code>dmidecode</code> command in the guest).  The
      optional <code>sysinfo</code> element covers all such categories
      of information. <span class="since">Since 0.8.7</span>
    </p>

<pre>
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...
&lt;os&gt;
  &lt;smbios mode='sysinfo'/&gt;
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  ...
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&lt;/os&gt;
&lt;sysinfo type='smbios'&gt;
  &lt;bios&gt;
    &lt;entry name='vendor'&gt;LENOVO&lt;/entry&gt;
  &lt;/bios&gt;
  &lt;system&gt;
    &lt;entry name='manufacturer'&gt;Fedora&lt;/entry&gt;
    &lt;entry name='product'&gt;Virt-Manager&lt;/entry&gt;
    &lt;entry name='version'&gt;0.9.4&lt;/entry&gt;
  &lt;/system&gt;
  &lt;baseBoard&gt;
    &lt;entry name='manufacturer'&gt;LENOVO&lt;/entry&gt;
    &lt;entry name='product'&gt;20BE0061MC&lt;/entry&gt;
    &lt;entry name='version'&gt;0B98401 Pro&lt;/entry&gt;
    &lt;entry name='serial'&gt;W1KS427111E&lt;/entry&gt;
  &lt;/baseBoard&gt;
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  &lt;chassis&gt;
    &lt;entry name='manufacturer'&gt;Dell Inc.&lt;/entry&gt;
    &lt;entry name='version'&gt;2.12&lt;/entry&gt;
    &lt;entry name='serial'&gt;65X0XF2&lt;/entry&gt;
    &lt;entry name='asset'&gt;40000101&lt;/entry&gt;
    &lt;entry name='sku'&gt;Type3Sku1&lt;/entry&gt;
  &lt;/chassis&gt;
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  &lt;oemStrings&gt;
    &lt;entry&gt;myappname:some arbitrary data&lt;/entry&gt;
    &lt;entry&gt;otherappname:more arbitrary data&lt;/entry&gt;
  &lt;/oemStrings&gt;
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&lt;/sysinfo&gt;
...</pre>
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    <p>
      The <code>sysinfo</code> element has a mandatory
      attribute <code>type</code> that determine the layout of
      sub-elements, with supported values of:
    </p>

    <dl>
      <dt><code>smbios</code></dt>
      <dd>Sub-elements call out specific SMBIOS values, which will
      affect the guest if used in conjunction with
      the <code>smbios</code> sub-element of
      the <a href="#elementsOS"><code>os</code></a> element.  Each
      sub-element of <code>sysinfo</code> names a SMBIOS block, and
      within those elements can be a list of <code>entry</code>
      elements that describe a field within the block.  The following
      blocks and entries are recognized:
        <dl>
          <dt><code>bios</code></dt>
          <dd>
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            This is block 0 of SMBIOS, with entry names drawn from:
            <dl>
               <dt><code>vendor</code></dt>
               <dd>BIOS Vendor's Name</dd>
               <dt><code>version</code></dt>
               <dd>BIOS Version</dd>
               <dt><code>date</code></dt>
               <dd>BIOS release date. If supplied, is in either mm/dd/yy or
                   mm/dd/yyyy format. If the year portion of the string is
                   two digits, the year is assumed to be 19yy.</dd>
               <dt><code>release</code></dt>
               <dd>System BIOS Major and Minor release number values
                   concatenated together as one string separated by
                   a period, for example, 10.22.</dd>
           </dl>
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          </dd>
          <dt><code>system</code></dt>
          <dd>
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            This is block 1 of SMBIOS, with entry names drawn from:
            <dl>
                <dt><code>manufacturer</code></dt>
                <dd>Manufacturer of BIOS</dd>
                <dt><code>product</code></dt>
                <dd>Product Name</dd>
                <dt><code>version</code></dt>
                <dd>Version of the product</dd>
                <dt><code>serial</code></dt>
                <dd>Serial number</dd>
                <dt><code>uuid</code></dt>
                <dd>Universal Unique ID number. If this entry is provided
                alongside a top-level
                <a href="#elementsMetadata"><code>uuid</code></a> element,
                then the two values must match.</dd>
                <dt><code>sku</code></dt>
                <dd>SKU number to identify a particular configuration.</dd>
                <dt><code>family</code></dt>
                <dd>Identify the family a particular computer belongs to.</dd>
            </dl>
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          </dd>
          <dt><code>baseBoard</code></dt>
          <dd>
            This is block 2 of SMBIOS. This element can be repeated multiple
            times to describe all the base boards; however, not all
            hypervisors necessarily support the repetition. The element can
            have the following children:
            <dl>
                <dt><code>manufacturer</code></dt>
                <dd>Manufacturer of BIOS</dd>
                <dt><code>product</code></dt>
                <dd>Product Name</dd>
                <dt><code>version</code></dt>
                <dd>Version of the product</dd>
                <dt><code>serial</code></dt>
                <dd>Serial number</dd>
                <dt><code>asset</code></dt>
                <dd>Asset tag</dd>
                <dt><code>location</code></dt>
                <dd>Location in chassis</dd>
            </dl>
            NB: Incorrectly supplied entries for the
            <code>bios</code>, <code>system</code> or <code>baseBoard</code>
            blocks will be ignored without error.  Other than <code>uuid</code>
            validation and <code>date</code> format checking, all values are
            passed as strings to the hypervisor driver.
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          </dd>
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          <dt><code>chassis</code></dt>
          <dd>
            <span class="since">Since 4.1.0,</span> this is block 3 of
            SMBIOS, with entry names drawn from:
            <dl>
                <dt><code>manufacturer</code></dt>
                <dd>Manufacturer of Chassis</dd>
                <dt><code>version</code></dt>
                <dd>Version of the Chassis</dd>
                <dt><code>serial</code></dt>
                <dd>Serial number</dd>
                <dt><code>asset</code></dt>
                <dd>Asset tag</dd>
                <dt><code>sku</code></dt>
                <dd>SKU number</dd>
            </dl>
          </dd>
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          <dt><code>oemStrings</code></dt>
          <dd>
            This is block 11 of SMBIOS. This element should appear once and
            can have multiple <code>entry</code> child elements, each providing
            arbitrary string data. There are no restrictions on what data can
            be provided in the entries, however, if the data is intended to be
            consumed by an application in the guest, it is recommended to use
            the application name as a prefix in the string. (<span class="since">Since 4.1.0</span>)
          </dd>
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        </dl>
      </dd>
    </dl>

570
    <h3><a id="elementsCPUAllocation">CPU Allocation</a></h3>
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572
<pre>
573
&lt;domain&gt;
574
  ...
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  &lt;vcpu placement='static' cpuset="1-4,^3,6" current="1"&gt;2&lt;/vcpu&gt;
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  &lt;vcpus&gt;
    &lt;vcpu id='0' enabled='yes' hotpluggable='no' order='1'/&gt;
    &lt;vcpu id='1' enabled='no' hotpluggable='yes'/&gt;
  &lt;/vcpus&gt;
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  ...
&lt;/domain&gt;
</pre>
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    <dl>
      <dt><code>vcpu</code></dt>
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      <dd>The content of this element defines the maximum number of virtual
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        CPUs allocated for the guest OS, which must be between 1 and
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        the maximum supported by the hypervisor.
        <dl>
         <dt><code>cpuset</code></dt>
         <dd>
           The optional attribute <code>cpuset</code> is a comma-separated
           list of physical CPU numbers that domain process and virtual CPUs
           can be pinned to by default. (NB: The pinning policy of domain
           process and virtual CPUs can be specified separately by
           <code>cputune</code>. If the attribute <code>emulatorpin</code>
           of <code>cputune</code> is specified, the <code>cpuset</code>
           specified by <code>vcpu</code> here will be ignored. Similarly,
           for virtual CPUs which have the <code>vcpupin</code> specified,
           the <code>cpuset</code> specified by <code>cpuset</code> here
           will be ignored. For virtual CPUs which don't have
           <code>vcpupin</code> specified, each will be pinned to the physical
           CPUs specified by <code>cpuset</code> here).
           Each element in that list is either a single CPU number,
           a range of CPU numbers, or a caret followed by a CPU number to
           be excluded from a previous range.
           <span class="since">Since 0.4.4</span>
         </dd>
         <dt><code>current</code></dt>
         <dd>
           The optional attribute <code>current</code> can
           be used to specify whether fewer than the maximum number of
           virtual CPUs should be enabled.
           <span class="since">Since 0.8.5</span>
         </dd>
         <dt><code>placement</code></dt>
         <dd>
           The optional attribute <code>placement</code> can be used to
           indicate the CPU placement mode for domain process. The value can
           be either "static" or "auto", but defaults to <code>placement</code>
           of <code>numatune</code> or "static" if <code>cpuset</code> is
           specified. Using "auto" indicates the domain process will be pinned
           to the advisory nodeset from querying numad and the value of
           attribute <code>cpuset</code> will be ignored if it's specified.
           If both <code>cpuset</code> and <code>placement</code> are not
           specified or if <code>placement</code> is "static", but no
           <code>cpuset</code> is specified, the domain process will be
           pinned to all the available physical CPUs.
           <span class="since">Since 0.9.11 (QEMU and KVM only)</span>
         </dd>
        </dl>
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      </dd>
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      <dt><code>vcpus</code></dt>
      <dd>
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        The vcpus element allows to control state of individual vCPUs.
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        The <code>id</code> attribute specifies the vCPU id as used by libvirt
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        in other places such as vCPU pinning, scheduler information and NUMA
        assignment. Note that the vCPU ID as seen in the guest may differ from
        libvirt ID in certain cases. Valid IDs are from 0 to the maximum vCPU
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        count as set by the <code>vcpu</code> element minus 1.

        The <code>enabled</code> attribute allows to control the state of the
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        vCPU. Valid values are <code>yes</code> and <code>no</code>.
645

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        <code>hotpluggable</code> controls whether given vCPU can be hotplugged
        and hotunplugged in cases when the CPU is enabled at boot. Note that
        all disabled vCPUs must be hotpluggable. Valid values are
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        <code>yes</code> and <code>no</code>.

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        <code>order</code> allows to specify the order to add the online vCPUs.
        For hypervisors/platforms that require to insert multiple vCPUs at once
        the order may be duplicated across all vCPUs that need to be
        enabled at once. Specifying order is not necessary, vCPUs are then
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        added in an arbitrary order. If order info is used, it must be used for
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        all online vCPUs. Hypervisors may clear or update ordering information
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        during certain operations to assure valid configuration.
658

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        Note that hypervisors may create hotpluggable vCPUs differently from
        boot vCPUs thus special initialization may be necessary.
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        Hypervisors may require that vCPUs enabled on boot which are not
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        hotpluggable are clustered at the beginning starting with ID 0. It may
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        be also required that vCPU 0 is always present and non-hotpluggable.
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        Note that providing state for individual CPUs may be necessary to enable
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        support of addressable vCPU hotplug and this feature may not be
        supported by all hypervisors.
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        For QEMU the following conditions are required. vCPU 0 needs to be
        enabled and non-hotpluggable. On PPC64 along with it vCPUs that are in
        the same core need to be enabled as well. All non-hotpluggable CPUs
        present at boot need to be grouped after vCPU 0.
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        <span class="since">Since 2.2.0 (QEMU only)</span>
      </dd>
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    </dl>

678
    <h3><a id="elementsIOThreadsAllocation">IOThreads Allocation</a></h3>
679 680 681 682 683 684 685 686 687 688 689 690 691
      <p>
        IOThreads are dedicated event loop threads for supported disk
        devices to perform block I/O requests in order to improve
        scalability especially on an SMP host/guest with many LUNs.
        <span class="since">Since 1.2.8 (QEMU only)</span>
      </p>

<pre>
&lt;domain&gt;
  ...
  &lt;iothreads&gt;4&lt;/iothreads&gt;
  ...
&lt;/domain&gt;
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</pre>
<pre>
&lt;domain&gt;
  ...
  &lt;iothreadids&gt;
    &lt;iothread id="2"/&gt;
    &lt;iothread id="4"/&gt;
    &lt;iothread id="6"/&gt;
    &lt;iothread id="8"/&gt;
  &lt;/iothreadids&gt;
  ...
&lt;/domain&gt;
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</pre>

    <dl>
      <dt><code>iothreads</code></dt>
      <dd>
        The content of this optional element defines the number
        of IOThreads to be assigned to the domain for use by
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        supported target storage devices. There
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        should be only 1 or 2 IOThreads per host CPU. There may be more
        than one supported device assigned to each IOThread.
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        <span class="since">Since 1.2.8</span>
715
      </dd>
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      <dt><code>iothreadids</code></dt>
      <dd>
        The optional <code>iothreadids</code> element provides the capability
        to specifically define the IOThread ID's for the domain.  By default,
        IOThread ID's are sequentially numbered starting from 1 through the
        number of <code>iothreads</code> defined for the domain. The
        <code>id</code> attribute is used to define the IOThread ID. The
        <code>id</code> attribute must be a positive integer greater than 0.
        If there are less <code>iothreadids</code> defined than
        <code>iothreads</code> defined for the domain, then libvirt will
        sequentially fill <code>iothreadids</code> starting at 1 avoiding
        any predefined <code>id</code>. If there are more
        <code>iothreadids</code> defined than <code>iothreads</code>
        defined for the domain, then the <code>iothreads</code> value
        will be adjusted accordingly.
        <span class="since">Since 1.2.15</span>
       </dd>
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    </dl>
734

735
    <h3><a id="elementsCPUTuning">CPU Tuning</a></h3>
736 737 738 739 740 741 742 743 744

<pre>
&lt;domain&gt;
  ...
  &lt;cputune&gt;
    &lt;vcpupin vcpu="0" cpuset="1-4,^2"/&gt;
    &lt;vcpupin vcpu="1" cpuset="0,1"/&gt;
    &lt;vcpupin vcpu="2" cpuset="2,3"/&gt;
    &lt;vcpupin vcpu="3" cpuset="0,4"/&gt;
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    &lt;emulatorpin cpuset="1-3"/&gt;
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    &lt;iothreadpin iothread="1" cpuset="5,6"/&gt;
    &lt;iothreadpin iothread="2" cpuset="7,8"/&gt;
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    &lt;shares&gt;2048&lt;/shares&gt;
    &lt;period&gt;1000000&lt;/period&gt;
    &lt;quota&gt;-1&lt;/quota&gt;
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    &lt;global_period&gt;1000000&lt;/global_period&gt;
    &lt;global_quota&gt;-1&lt;/global_quota&gt;
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    &lt;emulator_period&gt;1000000&lt;/emulator_period&gt;
    &lt;emulator_quota&gt;-1&lt;/emulator_quota&gt;
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    &lt;iothread_period&gt;1000000&lt;/iothread_period&gt;
    &lt;iothread_quota&gt;-1&lt;/iothread_quota&gt;
757 758
    &lt;vcpusched vcpus='0-4,^3' scheduler='fifo' priority='1'/&gt;
    &lt;iothreadsched iothreads='2' scheduler='batch'/&gt;
759 760 761
    &lt;cachetune vcpus='0-3'&gt;
      &lt;cache id='0' level='3' type='both' size='3' unit='MiB'/&gt;
      &lt;cache id='1' level='3' type='both' size='3' unit='MiB'/&gt;
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      &lt;monitor level='3' vcpus='1'/&gt;
      &lt;monitor level='3' vcpus='0-3'/&gt;
    &lt;/cachetune&gt;
    &lt;cachetune vcpus='4-5'&gt;
      &lt;monitor level='3' vcpus='4'/&gt;
      &lt;monitor level='3' vcpus='5'/&gt;
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    &lt;/cachetune&gt;
769 770 771 772
    &lt;memorytune vcpus='0-3'&gt;
      &lt;node id='0' bandwidth='60'/&gt;
    &lt;/memorytune&gt;

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  &lt;/cputune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
779
      <dt><code>cputune</code></dt>
780 781
      <dd>
         The optional <code>cputune</code> element provides details
782
         regarding the CPU tunable parameters for the domain.
783 784
         <span class="since">Since 0.9.0</span>
      </dd>
785
      <dt><code>vcpupin</code></dt>
786
      <dd>
787
        The optional <code>vcpupin</code> element specifies which of host's
788
        physical CPUs the domain vCPU will be pinned to. If this is omitted,
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        and attribute <code>cpuset</code> of element <code>vcpu</code> is
        not specified, the vCPU is pinned to all the physical CPUs by default.
        It contains two required attributes, the attribute <code>vcpu</code>
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        specifies vCPU id, and the attribute <code>cpuset</code> is same as
793 794
        attribute <code>cpuset</code> of element <code>vcpu</code>.
        (NB: Only qemu driver support)
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        <span class="since">Since 0.9.0</span>
       </dd>
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       <dt><code>emulatorpin</code></dt>
       <dd>
         The optional <code>emulatorpin</code> element specifies which of host
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         physical CPUs the "emulator", a subset of a domain not including vCPU
801
         or iothreads will be pinned to. If this is omitted, and attribute
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         <code>cpuset</code> of element <code>vcpu</code> is not specified,
         "emulator" is pinned to all the physical CPUs by default. It contains
         one required attribute <code>cpuset</code> specifying which physical
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         CPUs to pin to.
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       </dd>
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       <dt><code>iothreadpin</code></dt>
       <dd>
         The optional <code>iothreadpin</code> element specifies which of host
         physical CPUs the IOThreads will be pinned to. If this is omitted
         and attribute <code>cpuset</code> of element <code>vcpu</code> is
         not specified, the IOThreads are pinned to all the physical CPUs
         by default. There are two required attributes, the attribute
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         <code>iothread</code> specifies the IOThread ID and the attribute
         <code>cpuset</code> specifying which physical CPUs to pin to. See
         the <code>iothreadids</code>
         <a href="#elementsIOThreadsAllocation"><code>description</code></a>
         for valid <code>iothread</code> values.
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        <span class="since">Since 1.2.9</span>
       </dd>
821
      <dt><code>shares</code></dt>
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      <dd>
        The optional <code>shares</code> element specifies the proportional
824
        weighted share for the domain. If this is omitted, it defaults to
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        the OS provided defaults. NB, There is no unit for the value,
        it's a relative measure based on the setting of other VM,
        e.g. A VM configured with value
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        2048 will get twice as much CPU time as a VM configured with value 1024.
        <span class="since">Since 0.9.0</span>
      </dd>
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      <dt><code>period</code></dt>
      <dd>
        The optional <code>period</code> element specifies the enforcement
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        interval (unit: microseconds). Within <code>period</code>, each vCPU of
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        the domain will not be allowed to consume more than <code>quota</code>
        worth of runtime. The value should be in range [1000, 1000000]. A period
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        with value 0 means no value.
        <span class="since">Only QEMU driver support since 0.9.4, LXC since
        0.9.10</span>
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      </dd>
      <dt><code>quota</code></dt>
      <dd>
        The optional <code>quota</code> element specifies the maximum allowed
844
        bandwidth (unit: microseconds). A domain with <code>quota</code> as any
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        negative value indicates that the domain has infinite bandwidth for
        vCPU threads, which means that it is not bandwidth controlled. The value
        should be in range [1000, 18446744073709551] or less than 0. A quota
        with value 0 means no value. You can use this feature to ensure that all
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        vCPUs run at the same speed.
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        <span class="since">Only QEMU driver support since 0.9.4, LXC since
        0.9.10</span>
852
      </dd>
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      <dt><code>global_period</code></dt>
      <dd>
        The optional <code>global_period</code> element specifies the
        enforcement CFS scheduler interval (unit: microseconds) for the whole
        domain in contrast with <code>period</code> which enforces the interval
        per vCPU. The value should be in range 1000, 1000000]. A
        <code>global_period</code> with value 0 means no value.
        <span class="since">Only QEMU driver support since 1.3.3</span>
      </dd>
      <dt><code>global_quota</code></dt>
      <dd>
        The optional <code>global_quota</code> element specifies the maximum
        allowed bandwidth (unit: microseconds) within a period for the whole
        domain. A domain with <code>global_quota</code> as any negative
        value indicates that the domain has infinite bandwidth, which means that
        it is not bandwidth controlled. The value should be in range
        [1000, 18446744073709551] or less than 0. A <code>global_quota</code>
        with value 0 means no value.
        <span class="since">Only QEMU driver support since 1.3.3</span>
      </dd>
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      <dt><code>emulator_period</code></dt>
      <dd>
        The optional <code>emulator_period</code> element specifies the enforcement
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        interval (unit: microseconds). Within <code>emulator_period</code>, emulator
        threads (those excluding vCPUs) of the domain will not be allowed to consume
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        more than <code>emulator_quota</code> worth of runtime. The value should be
        in range [1000, 1000000]. A period with value 0 means no value.
        <span class="since">Only QEMU driver support since 0.10.0</span>
      </dd>
      <dt><code>emulator_quota</code></dt>
      <dd>
        The optional <code>emulator_quota</code> element specifies the maximum
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        allowed bandwidth (unit: microseconds) for domain's emulator threads (those
887
        excluding vCPUs). A domain with <code>emulator_quota</code> as any negative
888
        value indicates that the domain has infinite bandwidth for emulator threads
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        (those excluding vCPUs), which means that it is not bandwidth controlled.
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        The value should be in range [1000, 18446744073709551] or less than 0. A
        quota with value 0 means no value.
        <span class="since">Only QEMU driver support since 0.10.0</span>
      </dd>

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      <dt><code>iothread_period</code></dt>
      <dd>
        The optional <code>iothread_period</code> element specifies the
898
        enforcement interval (unit: microseconds) for IOThreads. Within
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        <code>iothread_period</code>, each IOThread of the domain will
        not be allowed to consume more than <code>iothread_quota</code>
        worth of runtime. The value should be in range [1000, 1000000].
        An iothread_period with value 0 means no value.
        <span class="since">Only QEMU driver support since 2.1.0</span>
      </dd>
      <dt><code>iothread_quota</code></dt>
      <dd>
        The optional <code>iothread_quota</code> element specifies the maximum
908
        allowed bandwidth (unit: microseconds) for IOThreads. A domain with
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        <code>iothread_quota</code> as any negative value indicates that the
        domain IOThreads have infinite bandwidth, which means that it is
        not bandwidth controlled. The value should be in range
        [1000, 18446744073709551] or less than 0. An <code>iothread_quota</code>
        with value 0 means no value. You can use this feature to ensure that
        all IOThreads run at the same speed.
        <span class="since">Only QEMU driver support since 2.1.0</span>
      </dd>

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      <dt><code>vcpusched</code> and <code>iothreadsched</code></dt>
      <dd>
        The optional <code>vcpusched</code> elements specifies the scheduler
        type (values <code>batch</code>, <code>idle</code>, <code>fifo</code>,
        <code>rr</code>) for particular vCPU/IOThread threads (based on
        <code>vcpus</code> and <code>iothreads</code>, leaving out
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        <code>vcpus</code>/<code>iothreads</code> sets the default). Valid
        <code>vcpus</code> values start at 0 through one less than the
        number of vCPU's defined for the domain. Valid <code>iothreads</code>
        values are described in the <code>iothreadids</code>
        <a href="#elementsIOThreadsAllocation"><code>description</code></a>.
        If no <code>iothreadids</code> are defined, then libvirt numbers
        IOThreads from 1 to the number of <code>iothreads</code> available
        for the domain. For real-time schedulers (<code>fifo</code>,
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        <code>rr</code>), priority must be specified as
933 934
        well (and is ignored for non-real-time ones). The value range
        for the priority depends on the host kernel (usually 1-99).
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        <span class="since">Since 1.2.13</span>
936 937
      </dd>

938 939 940 941 942 943 944 945
      <dt><code>cachetune</code><span class="since">Since 4.1.0</span></dt>
      <dd>
        Optional <code>cachetune</code> element can control allocations for CPU
        caches using the resctrl on the host. Whether or not is this supported
        can be gathered from capabilities where some limitations like minimum
        size and required granularity are reported as well. The required
        attribute <code>vcpus</code> specifies to which vCPUs this allocation
        applies. A vCPU can only be member of one <code>cachetune</code> element
946 947 948
        allocation. The vCPUs specified by cachetune can be identical with those
        in memorytune, however they are not allowed to overlap.
        Supported subelements are:
949 950 951
        <dl>
          <dt><code>cache</code></dt>
          <dd>
952 953
            This optional element controls the allocation of CPU cache and has
            the following attributes:
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            <dl>
              <dt><code>level</code></dt>
              <dd>
                Host cache level from which to allocate.
              </dd>
              <dt><code>id</code></dt>
              <dd>
                Host cache id from which to allocate.
              </dd>
              <dt><code>type</code></dt>
              <dd>
                Type of allocation. Can be <code>code</code> for code
                (instructions), <code>data</code> for data or <code>both</code>
                for both code and data (unified). Currently the allocation can
                be done only with the same type as the host supports, meaning
                you cannot request <code>both</code> for host with CDP
                (code/data prioritization) enabled.
              </dd>
              <dt><code>size</code></dt>
              <dd>
                The size of the region to allocate. The value by default is in
                bytes, but the <code>unit</code> attribute can be used to scale
                the value.
              </dd>
              <dt><code>unit</code> (optional)</dt>
              <dd>
                If specified it is the unit such as KiB, MiB, GiB, or TiB
                (described in the <code>memory</code> element
                for <a href="#elementsMemoryAllocation">Memory Allocation</a>)
                in which <code>size</code> is specified, defaults to bytes.
              </dd>
            </dl>
          </dd>
987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006
          <dt><code>monitor</code><span class="since">Since 4.10.0</span></dt>
          <dd>
            The optional element <code>monitor</code> creates the cache
            monitor(s) for current cache allocation and has the following
            required attributes:
            <dl>
              <dt><code>level</code></dt>
              <dd>
                Host cache level the monitor belongs to.
              </dd>
              <dt><code>vcpus</code></dt>
              <dd>
                vCPU list the monitor applies to. A monitor's vCPU list
                can only be the member(s) of the vCPU list of the associated
                allocation. The default monitor has the same vCPU list as the
                associated allocation. For non-default monitors, overlapping
                vCPUs are not permitted.
              </dd>
            </dl>
          </dd>
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        </dl>
1008
      </dd>
1009

1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039
      <dt><code>memorytune</code><span class="since">Since 4.7.0</span></dt>
      <dd>
        Optional <code>memorytune</code> element can control allocations for
        memory bandwidth using the resctrl on the host. Whether or not is this
        supported can be gathered from capabilities where some limitations like
        minimum bandwidth and required granularity are reported as well. The
        required attribute <code>vcpus</code> specifies to which vCPUs this
        allocation applies. A vCPU can only be member of one
        <code>memorytune</code> element allocation. The <code>vcpus</code> specified
        by <code>memorytune</code> can be identical to those specified by
        <code>cachetune</code>. However they are not allowed to overlap each other.
        Supported subelements are:
        <dl>
          <dt><code>node</code></dt>
          <dd>
            This element controls the allocation of CPU memory bandwidth and has the
            following attributes:
            <dl>
              <dt><code>id</code></dt>
              <dd>
                Host node id from which to allocate memory bandwidth.
              </dd>
              <dt><code>bandwidth</code></dt>
              <dd>
                The memory bandwidth to allocate from this node. The value by default
                is in percentage.
              </dd>
            </dl>
          </dd>
        </dl>
1040
      </dd>
1041 1042 1043
    </dl>


1044
    <h3><a id="elementsMemoryAllocation">Memory Allocation</a></h3>
1045 1046 1047 1048

<pre>
&lt;domain&gt;
  ...
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  &lt;maxMemory slots='16' unit='KiB'&gt;1524288&lt;/maxMemory&gt;
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  &lt;memory unit='KiB'&gt;524288&lt;/memory&gt;
  &lt;currentMemory unit='KiB'&gt;524288&lt;/currentMemory&gt;
1052 1053 1054 1055 1056 1057
  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>memory</code></dt>
1058 1059 1060
      <dd>The maximum allocation of memory for the guest at boot time. The
        memory allocation includes possible additional memory devices specified
        at start or hotplugged later.
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        The units for this value are determined by the optional
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        attribute <code>unit</code>, which defaults to "KiB"
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        (kibibytes, 2<sup>10</sup> or blocks of 1024 bytes).  Valid
        units are "b" or "bytes" for bytes, "KB" for kilobytes
        (10<sup>3</sup> or 1,000 bytes), "k" or "KiB" for kibibytes
        (1024 bytes), "MB" for megabytes (10<sup>6</sup> or 1,000,000
        bytes), "M" or "MiB" for mebibytes (2<sup>20</sup> or
        1,048,576 bytes), "GB" for gigabytes (10<sup>9</sup> or
        1,000,000,000 bytes), "G" or "GiB" for gibibytes
        (2<sup>30</sup> or 1,073,741,824 bytes), "TB" for terabytes
        (10<sup>12</sup> or 1,000,000,000,000 bytes), or "T" or "TiB"
        for tebibytes (2<sup>40</sup> or 1,099,511,627,776 bytes).
        However, the value will be rounded up to the nearest kibibyte
        by libvirt, and may be further rounded to the granularity
        supported by the hypervisor.  Some hypervisors also enforce a
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        minimum, such as 4000KiB.

1078 1079 1080
        In case <a href="#elementsCPU">NUMA</a> is configured for the guest the
        <code>memory</code> element can be omitted.

1081 1082 1083 1084 1085 1086 1087
        In the case of crash, optional attribute <code>dumpCore</code>
        can be used to control whether the guest memory should be
        included in the generated coredump or not (values "on", "off").

        <span class='since'><code>unit</code> since 0.9.11</span>,
        <span class='since'><code>dumpCore</code> since 0.10.2
        (QEMU only)</span></dd>
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      <dt><code>maxMemory</code></dt>
      <dd>The run time maximum memory allocation of the guest. The initial
        memory specified by either the <code>&lt;memory&gt;</code> element or
        the NUMA cell size configuration can be increased by hot-plugging of
        memory to the limit specified by this element.

        The <code>unit</code> attribute behaves the same as for
        <code>&lt;memory&gt;</code>.

        The <code>slots</code> attribute specifies the number of slots
        available for adding memory to the guest. The bounds are hypervisor
        specific.

        Note that due to alignment of the memory chunks added via memory
        hotplug the full size allocation specified by this element may be
        impossible to achieve.
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        <span class='since'>Since 1.2.14 supported by the QEMU driver.</span>
1105 1106
      </dd>

1107 1108 1109 1110
      <dt><code>currentMemory</code></dt>
      <dd>The actual allocation of memory for the guest. This value can
        be less than the maximum allocation, to allow for ballooning
        up the guests memory on the fly. If this is omitted, it defaults
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        to the same value as the <code>memory</code> element.
        The <code>unit</code> attribute behaves the same as
        for <code>memory</code>.</dd>
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    </dl>


1117
    <h3><a id="elementsMemoryBacking">Memory Backing</a></h3>
1118 1119 1120 1121 1122

<pre>
&lt;domain&gt;
  ...
  &lt;memoryBacking&gt;
1123 1124 1125
    &lt;hugepages&gt;
      &lt;page size="1" unit="G" nodeset="0-3,5"/&gt;
      &lt;page size="2" unit="M" nodeset="4"/&gt;
1126
    &lt;/hugepages&gt;
1127
    &lt;nosharepages/&gt;
1128
    &lt;locked/&gt;
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    &lt;source type="file|anonymous|memfd"/&gt;
1130 1131
    &lt;access mode="shared|private"/&gt;
    &lt;allocation mode="immediate|ondemand"/&gt;
1132
    &lt;discard/&gt;
1133 1134 1135 1136 1137
  &lt;/memoryBacking&gt;
  ...
&lt;/domain&gt;
</pre>

1138 1139 1140 1141
    <p>The optional <code>memoryBacking</code> element may contain several
      elements that influence how virtual memory pages are backed by host
      pages.</p>

1142
    <dl>
1143 1144
      <dt><code>hugepages</code></dt>
      <dd>This tells the hypervisor that the guest should have its memory
1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157
      allocated using hugepages instead of the normal native page size.
      <span class='since'>Since 1.2.5</span> it's possible to set hugepages
      more specifically per numa node. The <code>page</code> element is
      introduced. It has one compulsory attribute <code>size</code> which
      specifies which hugepages should be used (especially useful on systems
      supporting hugepages of different sizes). The default unit for the
      <code>size</code> attribute is kilobytes (multiplier of 1024). If you
      want to use different unit, use optional <code>unit</code> attribute.
      For systems with NUMA, the optional <code>nodeset</code> attribute may
      come handy as it ties given guest's NUMA nodes to certain hugepage
      sizes. From the example snippet, one gigabyte hugepages are used for
      every NUMA node except node number four. For the correct syntax see
      <a href="#elementsNUMATuning">this</a>.</dd>
1158 1159 1160 1161 1162 1163
      <dt><code>nosharepages</code></dt>
      <dd>Instructs hypervisor to disable shared pages (memory merge, KSM) for
        this domain. <span class="since">Since 1.0.6</span></dd>
      <dt><code>locked</code></dt>
      <dd>When set and supported by the hypervisor, memory pages belonging
        to the domain will be locked in host's memory and the host will not
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        be allowed to swap them out, which might be required for some
        workloads such as real-time. For QEMU/KVM guests, the memory used by
        the QEMU process itself will be locked too: unlike guest memory, this
        is an amount libvirt has no way of figuring out in advance, so it has
        to remove the limit on locked memory altogether. Thus, enabling this
        option opens up to a potential security risk: the host will be unable
        to reclaim the locked memory back from the guest when it's running out
        of memory, which means a malicious guest allocating large amounts of
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        locked memory could cause a denial-of-service attack on the host.
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        Because of this, using this option is discouraged unless your workload
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        demands it; even then, it's highly recommended to set a
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        <code>hard_limit</code> (see
        <a href="#elementsMemoryTuning">memory tuning</a>) on memory allocation
        suitable for the specific environment at the same time to mitigate
        the risks described above. <span class="since">Since 1.0.6</span></dd>
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       <dt><code>source</code></dt>
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       <dd>Using the <code>type</code> attribute, it's possible to
       provide "file" to utilize file memorybacking or keep the
       default "anonymous". <span class="since">Since 4.10.0</span>,
       you may choose "memfd" backing. (QEMU/KVM only)</dd>
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       <dt><code>access</code></dt>
1185 1186 1187
       <dd>Using the <code>mode</code> attribute, specify if the memory is
         to be "shared" or "private". This can be overridden per numa node by
         <code>memAccess</code>.</dd>
1188
       <dt><code>allocation</code></dt>
1189 1190
       <dd>Using the <code>mode</code> attribute, specify when to allocate
         the memory by supplying either "immediate" or "ondemand".</dd>
1191 1192 1193 1194 1195 1196 1197 1198
       <dt><code>discard</code></dt>
       <dd>When set and supported by hypervisor the memory
         content is discarded just before guest shuts down (or
         when DIMM module is unplugged). Please note that this is
         just an optimization and is not guaranteed to work in
         all cases (e.g. when hypervisor crashes).
         <span class="since">Since 4.4.0</span> (QEMU/KVM only)
       </dd>
1199 1200 1201
    </dl>


1202
    <h3><a id="elementsMemoryTuning">Memory Tuning</a></h3>
1203 1204 1205 1206 1207

<pre>
&lt;domain&gt;
  ...
  &lt;memtune&gt;
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    &lt;hard_limit unit='G'&gt;1&lt;/hard_limit&gt;
    &lt;soft_limit unit='M'&gt;128&lt;/soft_limit&gt;
    &lt;swap_hard_limit unit='G'&gt;2&lt;/swap_hard_limit&gt;
    &lt;min_guarantee unit='bytes'&gt;67108864&lt;/min_guarantee&gt;
1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
  &lt;/memtune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>memtune</code></dt>
      <dd> The optional <code>memtune</code> element provides details
        regarding the memory tunable parameters for the domain. If this is
        omitted, it defaults to the OS provided defaults. For QEMU/KVM, the
        parameters are applied to the QEMU process as a whole. Thus, when
        counting them, one needs to add up guest RAM, guest video RAM, and
        some memory overhead of QEMU itself. The last piece is hard to
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        determine so one needs guess and try.  For each tunable, it
        is possible to designate which unit the number is in on
        input, using the same values as
        for <code>&lt;memory&gt;</code>.  For backwards
        compatibility, output is always in
        KiB.  <span class='since'><code>unit</code>
1231 1232 1233
        since 0.9.11</span>
        Possible values for all *_limit parameters are in range from 0 to
        VIR_DOMAIN_MEMORY_PARAM_UNLIMITED.</dd>
1234 1235
      <dt><code>hard_limit</code></dt>
      <dd> The optional <code>hard_limit</code> element is the maximum memory
1236
        the guest can use. The units for this value are kibibytes (i.e. blocks
1237 1238 1239
        of 1024 bytes). Users of QEMU and KVM are strongly advised not to set
        this limit as domain may get killed by the kernel if the guess is too
        low, and determining the memory needed for a process to run is an
1240
        <a href="http://en.wikipedia.org/wiki/Undecidable_problem">
1241 1242 1243 1244 1245
        undecidable problem</a>; that said, if you already set
        <code>locked</code> in
        <a href="#elementsMemoryBacking">memory backing</a> because your
        workload demands it, you'll have to take into account the specifics of
        your deployment and figure out a value for <code>hard_limit</code> that
1246 1247 1248
        is large enough to support the memory requirements of your guest, but
        small enough to protect your host against a malicious guest locking all
        memory.</dd>
1249 1250 1251
      <dt><code>soft_limit</code></dt>
      <dd> The optional <code>soft_limit</code> element is the memory limit to
        enforce during memory contention. The units for this value are
1252
        kibibytes (i.e. blocks of 1024 bytes)</dd>
1253 1254 1255
      <dt><code>swap_hard_limit</code></dt>
      <dd> The optional <code>swap_hard_limit</code> element is the maximum
        memory plus swap the guest can use. The units for this value are
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        kibibytes (i.e. blocks of 1024 bytes). This has to be more than
1257 1258 1259 1260
        hard_limit value provided</dd>
      <dt><code>min_guarantee</code></dt>
      <dd> The optional <code>min_guarantee</code> element is the guaranteed
        minimum memory allocation for the guest. The units for this value are
1261 1262
        kibibytes (i.e. blocks of 1024 bytes). This element is only supported
        by VMware ESX and OpenVZ drivers.</dd>
1263 1264 1265
    </dl>


1266
    <h3><a id="elementsNUMATuning">NUMA Node Tuning</a></h3>
1267 1268 1269 1270 1271 1272

<pre>
&lt;domain&gt;
  ...
  &lt;numatune&gt;
    &lt;memory mode="strict" nodeset="1-4,^3"/&gt;
1273 1274
    &lt;memnode cellid="0" mode="strict" nodeset="1"/&gt;
    &lt;memnode cellid="2" mode="preferred" nodeset="2"/&gt;
1275 1276 1277 1278 1279 1280
  &lt;/numatune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
1281 1282 1283 1284 1285 1286
      <dt><code>numatune</code></dt>
      <dd>
        The optional <code>numatune</code> element provides details of
        how to tune the performance of a NUMA host via controlling NUMA policy
        for domain process. NB, only supported by QEMU driver.
        <span class='since'>Since 0.9.3</span>
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      </dd>
1288 1289
      <dt><code>memory</code></dt>
      <dd>
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        The optional <code>memory</code> element specifies how to allocate memory
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        for the domain process on a NUMA host. It contains several optional
        attributes. Attribute <code>mode</code> is either 'interleave',
        'strict', or 'preferred', defaults to 'strict'. Attribute
        <code>nodeset</code> specifies the NUMA nodes, using the same syntax as
        attribute <code>cpuset</code> of element <code>vcpu</code>. Attribute
        <code>placement</code> (<span class='since'>since 0.9.12</span>) can be
        used to indicate the memory placement mode for domain process, its value
        can be either "static" or "auto", defaults to <code>placement</code> of
        <code>vcpu</code>, or "static" if <code>nodeset</code> is specified.
        "auto" indicates the domain process will only allocate memory from the
        advisory nodeset returned from querying numad, and the value of attribute
        <code>nodeset</code> will be ignored if it's specified.

        If <code>placement</code> of <code>vcpu</code> is 'auto', and
        <code>numatune</code> is not specified, a default <code>numatune</code>
        with <code>placement</code> 'auto' and <code>mode</code> 'strict' will
        be added implicitly.

1309 1310
        <span class='since'>Since 0.9.3</span>
      </dd>
1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323
      <dt><code>memnode</code></dt>
      <dd>
        Optional <code>memnode</code> elements can specify memory allocation
        policies per each guest NUMA node.  For those nodes having no
        corresponding <code>memnode</code> element, the default from
        element <code>memory</code> will be used.  Attribute <code>cellid</code>
        addresses guest NUMA node for which the settings are applied.
        Attributes <code>mode</code> and <code>nodeset</code> have the same
        meaning and syntax as in <code>memory</code> element.

        This setting is not compatible with automatic placement.
        <span class='since'>QEMU Since 1.2.7</span>
      </dd>
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    </dl>

1326

1327
    <h3><a id="elementsBlockTuning">Block I/O Tuning</a></h3>
1328 1329 1330 1331 1332
<pre>
&lt;domain&gt;
  ...
  &lt;blkiotune&gt;
    &lt;weight&gt;800&lt;/weight&gt;
1333 1334 1335 1336 1337 1338 1339
    &lt;device&gt;
      &lt;path&gt;/dev/sda&lt;/path&gt;
      &lt;weight&gt;1000&lt;/weight&gt;
    &lt;/device&gt;
    &lt;device&gt;
      &lt;path&gt;/dev/sdb&lt;/path&gt;
      &lt;weight&gt;500&lt;/weight&gt;
1340 1341 1342 1343
      &lt;read_bytes_sec&gt;10000&lt;/read_bytes_sec&gt;
      &lt;write_bytes_sec&gt;10000&lt;/write_bytes_sec&gt;
      &lt;read_iops_sec&gt;20000&lt;/read_iops_sec&gt;
      &lt;write_iops_sec&gt;20000&lt;/write_iops_sec&gt;
1344
    &lt;/device&gt;
1345 1346 1347 1348 1349 1350 1351 1352 1353
  &lt;/blkiotune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>blkiotune</code></dt>
      <dd> The optional <code>blkiotune</code> element provides the ability
        to tune Blkio cgroup tunable parameters for the domain. If this is
1354 1355
        omitted, it defaults to the OS provided
        defaults. <span class="since">Since 0.8.8</span></dd>
1356
      <dt><code>weight</code></dt>
1357 1358
      <dd> The optional <code>weight</code> element is the overall I/O
        weight of the guest. The value should be in the range [100,
1359 1360
        1000]. After kernel 2.6.39, the value could be in the
        range [10, 1000].</dd>
1361 1362 1363 1364 1365 1366 1367 1368
      <dt><code>device</code></dt>
      <dd>The domain may have multiple <code>device</code> elements
        that further tune the weights for each host block device in
        use by the domain.  Note that
        multiple <a href="#elementsDisks">guest disks</a> can share a
        single host block device, if they are backed by files within
        the same host file system, which is why this tuning parameter
        is at the global domain level rather than associated with each
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        guest disk device (contrast this to
        the <a href="#elementsDisks"><code>&lt;iotune&gt;</code></a>
        element which can apply to an
        individual <code>&lt;disk&gt;</code>).
        Each <code>device</code> element has two
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        mandatory sub-elements, <code>path</code> describing the
        absolute path of the device, and <code>weight</code> giving
        the relative weight of that device, in the range [100,
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        1000]. After kernel 2.6.39, the value could be in the
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        range [10, 1000]. <span class="since">Since 0.9.8</span><br/>
        Additionally, the following optional sub-elements can be used:
        <dl>
          <dt><code>read_bytes_sec</code></dt>
          <dd>Read throughput limit in bytes per second.
            <span class="since">Since 1.2.2</span></dd>
          <dt><code>write_bytes_sec</code></dt>
          <dd>Write throughput limit in bytes per second.
            <span class="since">Since 1.2.2</span></dd>
          <dt><code>read_iops_sec</code></dt>
          <dd>Read I/O operations per second limit.
            <span class="since">Since 1.2.2</span></dd>
          <dt><code>write_iops_sec</code></dt>
          <dd>Write I/O operations per second limit.
            <span class="since">Since 1.2.2</span></dd>
      </dl></dd></dl>
1394 1395


1396
    <h3><a id="resPartition">Resource partitioning</a></h3>
1397 1398 1399 1400 1401 1402

    <p>
      Hypervisors may allow for virtual machines to be placed into
      resource partitions, potentially with nesting of said partitions.
      The <code>resource</code> element groups together configuration
      related to resource partitioning. It currently supports a child
1403
      element <code>partition</code> whose content defines the absolute path
1404 1405 1406 1407 1408 1409 1410 1411
      of the resource partition in which to place the domain. If no
      partition is listed, then the domain will be placed in a default
      partition. It is the responsibility of the app/admin to ensure
      that the partition exists prior to starting the guest. Only the
      (hypervisor specific) default partition can be assumed to exist
      by default.
    </p>
<pre>
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...
&lt;resource&gt;
  &lt;partition&gt;/virtualmachines/production&lt;/partition&gt;
&lt;/resource&gt;
...
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</pre>

    <p>
      Resource partitions are currently supported by the QEMU and
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      LXC drivers, which map partition paths to cgroups directories,
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      in all mounted controllers. <span class="since">Since 1.0.5</span>
    </p>

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    <h3><a id="elementsCPU">CPU model and topology</a></h3>
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    <p>
      Requirements for CPU model, its features and topology can be specified
      using the following collection of elements.
      <span class="since">Since 0.7.5</span>
    </p>

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<pre>
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...
&lt;cpu match='exact'&gt;
  &lt;model fallback='allow'&gt;core2duo&lt;/model&gt;
  &lt;vendor&gt;Intel&lt;/vendor&gt;
  &lt;topology sockets='1' cores='2' threads='1'/&gt;
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  &lt;cache level='3' mode='emulate'/&gt;
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  &lt;feature policy='disable' name='lahf_lm'/&gt;
&lt;/cpu&gt;
...</pre>
1443

1444
<pre>
1445 1446 1447 1448 1449
&lt;cpu mode='host-model'&gt;
  &lt;model fallback='forbid'/&gt;
  &lt;topology sockets='1' cores='2' threads='1'/&gt;
&lt;/cpu&gt;
...</pre>
1450 1451

<pre>
1452
&lt;cpu mode='host-passthrough'&gt;
1453
  &lt;cache mode='passthrough'/&gt;
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  &lt;feature policy='disable' name='lahf_lm'/&gt;
...</pre>
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    <p>
      In case no restrictions need to be put on CPU model and its features, a
      simpler <code>cpu</code> element can be used.
      <span class="since">Since 0.7.6</span>
    </p>

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<pre>
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...
&lt;cpu&gt;
  &lt;topology sockets='1' cores='2' threads='1'/&gt;
&lt;/cpu&gt;
...</pre>
1469 1470 1471 1472

    <dl>
      <dt><code>cpu</code></dt>
      <dd>The <code>cpu</code> element is the main container for describing
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        guest CPU requirements. Its <code>match</code> attribute specifies how
        strictly the virtual CPU provided to the guest matches these
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        requirements. <span class="since">Since 0.7.6</span> the
        <code>match</code> attribute can be omitted if <code>topology</code>
        is the only element within <code>cpu</code>. Possible values for the
        <code>match</code> attribute are:

        <dl>
          <dt><code>minimum</code></dt>
          <dd>The specified CPU model and features describes the minimum
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            requested CPU. A better CPU will be provided to the guest if it
            is possible with the requested hypervisor on the current host.
            This is a constrained <code>host-model</code> mode; the domain
            will not be created if the provided virtual CPU does not meet
            the requirements.</dd>

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          <dt><code>exact</code></dt>
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          <dd>The virtual CPU provided to the guest should exactly match the
            specification. If such CPU is not supported, libvirt will refuse
            to start the domain.</dd>

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          <dt><code>strict</code></dt>
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          <dd>The domain will not be created unless the host CPU exactly
            matches the specification. This is not very useful in practice
            and should only be used if there is a real reason.</dd>
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        </dl>
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        <span class="since">Since 0.8.5</span> the <code>match</code>
        attribute can be omitted and will default to <code>exact</code>.
1502

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        Sometimes the hypervisor is not able to create a virtual CPU exactly
        matching the specification passed by libvirt.
        <span class="since">Since 3.2.0</span>, an optional <code>check</code>
        attribute can be used to request a specific way of checking whether
        the virtual CPU matches the specification. It is usually safe to omit
        this attribute when starting a domain and stick with the default
        value. Once the domain starts, libvirt will automatically change the
        <code>check</code> attribute to the best supported value to ensure the
        virtual CPU does not change when the domain is migrated to another
        host. The following values can be used:

        <dl>
          <dt><code>none</code></dt>
          <dd>Libvirt does no checking and it is up to the hypervisor to
            refuse to start the domain if it cannot provide the requested CPU.
            With QEMU this means no checking is done at all since the default
            behavior of QEMU is to emit warnings, but start the domain anyway.
          </dd>

          <dt><code>partial</code></dt>
          <dd>Libvirt will check the guest CPU specification before starting
            a domain, but the rest is left on the hypervisor. It can still
            provide a different virtual CPU.</dd>

          <dt><code>full</code></dt>
          <dd>The virtual CPU created by the hypervisor will be checked
            against the CPU specification and the domain will not be started
            unless the two CPUs match.</dd>
        </dl>

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        <span class="since">Since 0.9.10</span>, an optional <code>mode</code>
        attribute may be used to make it easier to configure a guest CPU to be
        as close to host CPU as possible. Possible values for the
        <code>mode</code> attribute are:

        <dl>
          <dt><code>custom</code></dt>
          <dd>In this mode, the <code>cpu</code> element describes the CPU
          that should be presented to the guest. This is the default when no
          <code>mode</code> attribute is specified. This mode makes it so that
          a persistent guest will see the same hardware no matter what host
          the guest is booted on.</dd>
          <dt><code>host-model</code></dt>
          <dd>The <code>host-model</code> mode is essentially a shortcut to
          copying host CPU definition from capabilities XML into domain XML.
          Since the CPU definition is copied just before starting a domain,
          exactly the same XML can be used on different hosts while still
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          providing the best guest CPU each host supports. The
          <code>match</code> attribute can't be used in this mode. Specifying
          CPU model is not supported either, but <code>model</code>'s
          <code>fallback</code> attribute may still be used. Using the
          <code>feature</code> element, specific flags may be enabled or
          disabled specifically in addition to the host model. This may be
          used to fine tune features that can be emulated.
          <span class="since">(Since 1.1.1)</span>.
          Libvirt does not model every aspect of each CPU so
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          the guest CPU will not match the host CPU exactly. On the other
          hand, the ABI provided to the guest is reproducible. During
          migration, complete CPU model definition is transferred to the
          destination host so the migrated guest will see exactly the same CPU
          model even if the destination host contains more capable CPUs for
          the running instance of the guest; but shutting down and restarting
          the guest may present different hardware to the guest according to
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          the capabilities of the new host. Prior to libvirt 3.2.0 and QEMU
          2.9.0 detection of the host CPU model via QEMU is not supported.
          Thus the CPU configuration created using <code>host-model</code>
          may not work as expected.
          <span class="since">Since 3.2.0 and QEMU 2.9.0</span> this mode
          works the way it was designed and it is indicated by the
          <code>fallback</code> attribute set to <code>forbid</code> in the
          host-model CPU definition advertised in
          <a href="formatdomaincaps.html#elementsCPU">domain capabilities XML</a>.
          When <code>fallback</code> attribute is set to <code>allow</code>
          in the domain capabilities XML, it is recommended to use
          <code>custom</code> mode with just the CPU model from the host
          capabilities XML. <span class="since">Since 1.2.11</span> PowerISA
          allows processors to run VMs in binary compatibility mode supporting
          an older version of ISA.  Libvirt on PowerPC architecture uses the
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          <code>host-model</code> to signify a guest mode CPU running in
          binary compatibility mode. Example:
          When a user needs a power7 VM to run in compatibility mode
          on a Power8 host, this can be described in XML as follows :
<pre>
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&lt;cpu mode='host-model'&gt;
  &lt;model&gt;power7&lt;/model&gt;
&lt;/cpu&gt;
...</pre>
1590
          </dd>
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          <dt><code>host-passthrough</code></dt>
          <dd>With this mode, the CPU visible to the guest should be exactly
          the same as the host CPU even in the aspects that libvirt does not
          understand. Though the downside of this mode is that the guest
          environment cannot be reproduced on different hardware. Thus, if you
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          hit any bugs, you are on your own. Further details of that CPU can
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          be changed using <code>feature</code> elements. Migration of a guest
          using host-passthrough is dangerous if the source and destination
          hosts are not identical in both hardware and configuration. If such
          a migration is attempted then the guest may hang or crash upon
          resuming execution on the destination host.</dd>
1602
        </dl>
1603 1604 1605 1606 1607 1608 1609 1610 1611

        Both <code>host-model</code> and <code>host-passthrough</code> modes
        make sense when a domain can run directly on the host CPUs (for
        example, domains with type <code>kvm</code>). The actual host CPU is
        irrelevant for domains with emulated virtual CPUs (such as domains with
        type <code>qemu</code>). However, for backward compatibility
        <code>host-model</code> may be implemented even for domains running on
        emulated CPUs in which case the best CPU the hypervisor is able to
        emulate may be used rather then trying to mimic the host CPU model.
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      </dd>

      <dt><code>model</code></dt>
      <dd>The content of the <code>model</code> element specifies CPU model
        requested by the guest. The list of available CPU models and their
        definition can be found in <code>cpu_map.xml</code> file installed
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        in libvirt's data directory. If a hypervisor is not able to use the
        exact CPU model, libvirt automatically falls back to a closest model
        supported by the hypervisor while maintaining the list of CPU
        features. <span class="since">Since 0.9.10</span>, an optional
        <code>fallback</code> attribute can be used to forbid this behavior,
        in which case an attempt to start a domain requesting an unsupported
        CPU model will fail. Supported values for <code>fallback</code>
        attribute are: <code>allow</code> (this is the default), and
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        <code>forbid</code>. The optional <code>vendor_id</code> attribute
1627
        (<span class="since">Since 0.10.0</span>)  can be used to set the
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        vendor id seen by the guest. It must be exactly 12 characters long.
        If not set the vendor id of the host is used. Typical possible
        values are "AuthenticAMD" and "GenuineIntel".</dd>
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      <dt><code>vendor</code></dt>
      <dd><span class="since">Since 0.8.3</span> the content of the
        <code>vendor</code> element specifies CPU vendor requested by the
        guest. If this element is missing, the guest can be run on a CPU
        matching given features regardless on its vendor. The list of
        supported vendors can be found in <code>cpu_map.xml</code>.</dd>

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      <dt><code>topology</code></dt>
      <dd>The <code>topology</code> element specifies requested topology of
        virtual CPU provided to the guest. Three non-zero values have to be
        given for <code>sockets</code>, <code>cores</code>, and
        <code>threads</code>: total number of CPU sockets, number of cores per
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        socket, and number of threads per core, respectively. Hypervisors may
        require that the maximum number of vCPUs specified by the
        <code>cpus</code> element equals to the number of vcpus resulting
        from the topology.</dd>
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      <dt><code>feature</code></dt>
      <dd>The <code>cpu</code> element can contain zero or more
        <code>elements</code> used to fine-tune features provided by the
        selected CPU model. The list of known feature names can be found in
        the same file as CPU models. The meaning of each <code>feature</code>
        element depends on its <code>policy</code> attribute, which has to be
        set to one of the following values:

        <dl>
          <dt><code>force</code></dt>
          <dd>The virtual CPU will claim the feature is supported regardless
            of it being supported by host CPU.</dd>
          <dt><code>require</code></dt>
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          <dd>Guest creation will fail unless the feature is supported by the
            host CPU or the hypervisor is able to emulate it.</dd>
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          <dt><code>optional</code></dt>
          <dd>The feature will be supported by virtual CPU if and only if it
            is supported by host CPU.</dd>
          <dt><code>disable</code></dt>
          <dd>The feature will not be supported by virtual CPU.</dd>
          <dt><code>forbid</code></dt>
          <dd>Guest creation will fail if the feature is supported by host
            CPU.</dd>
        </dl>
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        <span class="since">Since 0.8.5</span> the <code>policy</code>
        attribute can be omitted and will default to <code>require</code>.
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        <p> Individual CPU feature names are specified as part of the
        <code>name</code> attribute. For example, to explicitly specify
        the 'pcid' feature with Intel IvyBridge CPU model:
        </p>

<pre>
...
&lt;cpu match='exact'&gt;
  &lt;model fallback='forbid'&gt;IvyBridge&lt;/model&gt;
  &lt;vendor&gt;Intel&lt;/vendor&gt;
  &lt;feature policy='require' name='pcid'/&gt;
&lt;/cpu&gt;
...</pre>

1691
      </dd>
1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724

      <dt><code>cache</code></dt>
      <dd><span class="since">Since 3.3.0</span> the <code>cache</code>
        element describes the virtual CPU cache. If the element is missing,
        the hypervisor will use a sensible default.

        <dl>
          <dt><code>level</code></dt>
          <dd>This optional attribute specifies which cache level is described
            by the element. Missing attribute means the element describes all
            CPU cache levels at once. Mixing <code>cache</code> elements with
            the <code>level</code> attribute set and those without the
            attribute is forbidden.</dd>

          <dt><code>mode</code></dt>
          <dd>
            The following values are supported:
            <dl>
              <dt><code>emulate</code></dt>
              <dd>The hypervisor will provide a fake CPU cache data.</dd>

              <dt><code>passthrough</code></dt>
              <dd>The real CPU cache data reported by the host CPU will be
                passed through to the virtual CPU.</dd>

              <dt><code>disable</code></dt>
              <dd>The virtual CPU will report no CPU cache of the specified
                level (or no cache at all if the <code>level</code> attribute
                is missing).</dd>
            </dl>
          </dd>
        </dl>
      </dd>
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    </dl>

1727
    <p>
1728
      Guest NUMA topology can be specified using the <code>numa</code> element.
1729 1730 1731 1732
      <span class="since">Since 0.9.8</span>
    </p>

<pre>
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...
&lt;cpu&gt;
1735
  ...
1736
  &lt;numa&gt;
1737
    &lt;cell id='0' cpus='0-3' memory='512000' unit='KiB' discard='yes'/&gt;
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    &lt;cell id='1' cpus='4-7' memory='512000' unit='KiB' memAccess='shared'/&gt;
  &lt;/numa&gt;
  ...
&lt;/cpu&gt;
...</pre>
1743 1744 1745

    <p>
      Each <code>cell</code> element specifies a NUMA cell or a NUMA node.
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      <code>cpus</code> specifies the CPU or range of CPUs that are
      part of the node. <code>memory</code> specifies the node memory
      in kibibytes (i.e. blocks of 1024 bytes).
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      <span class="since">Since 1.2.11</span> one can use an additional <a
          href="#elementsMemoryAllocation"><code>unit</code></a> attribute to
      define units in which <code>memory</code> is specified.
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      <span class="since">Since 1.2.7</span> all cells should
      have <code>id</code> attribute in case referring to some cell is
      necessary in the code, otherwise the cells are
      assigned <code>id</code>s in the increasing order starting from
      0.  Mixing cells with and without the <code>id</code> attribute
      is not recommended as it may result in unwanted behaviour.
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      <span class='since'>Since 1.2.9</span> the optional attribute
      <code>memAccess</code> can control whether the memory is to be
      mapped as "shared" or "private".  This is valid only for
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      hugepages-backed memory and nvdimm modules.
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      Each <code>cell</code> element can have an optional
      <code>discard</code> attribute which fine tunes the discard
      feature for given numa node as described under
      <a href="#elementsMemoryBacking">Memory Backing</a>.
      Accepted values are <code>yes</code> and <code>no</code>.
      <span class='since'>Since 4.4.0</span>
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    </p>

    <p>
1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832
      This guest NUMA specification is currently available only for
      QEMU/KVM and Xen.
    </p>

    <p>
      A NUMA hardware architecture supports the notion of distances
      between NUMA cells. <span class="since">Since 3.10.0</span> it
      is possible to define the distance between NUMA cells using the
      <code>distances</code> element within a NUMA <code>cell</code>
      description. The <code>sibling</code> sub-element is used to
      specify the distance value between sibling NUMA cells. For more
      details, see the chapter explaining the system's SLIT (System
      Locality Information Table) within the ACPI (Advanced
      Configuration and Power Interface) specification.
    </p>

<pre>
...
&lt;cpu&gt;
  ...
  &lt;numa&gt;
    &lt;cell id='0' cpus='0,4-7' memory='512000' unit='KiB'&gt;
      &lt;distances&gt;
        &lt;sibling id='0' value='10'/&gt;
        &lt;sibling id='1' value='21'/&gt;
        &lt;sibling id='2' value='31'/&gt;
        &lt;sibling id='3' value='41'/&gt;
      &lt;/distances&gt;
    &lt;/cell&gt;
    &lt;cell id='1' cpus='1,8-10,12-15' memory='512000' unit='KiB' memAccess='shared'&gt;
      &lt;distances&gt;
        &lt;sibling id='0' value='21'/&gt;
        &lt;sibling id='1' value='10'/&gt;
        &lt;sibling id='2' value='21'/&gt;
        &lt;sibling id='3' value='31'/&gt;
      &lt;/distances&gt;
    &lt;/cell&gt;
    &lt;cell id='2' cpus='2,11' memory='512000' unit='KiB' memAccess='shared'&gt;
      &lt;distances&gt;
        &lt;sibling id='0' value='31'/&gt;
        &lt;sibling id='1' value='21'/&gt;
        &lt;sibling id='2' value='10'/&gt;
        &lt;sibling id='3' value='21'/&gt;
      &lt;/distances&gt;
    &lt;/cell&gt;
    &lt;cell id='3' cpus='3' memory='512000' unit='KiB'&gt;
      &lt;distances&gt;
        &lt;sibling id='0' value='41'/&gt;
        &lt;sibling id='1' value='31'/&gt;
        &lt;sibling id='2' value='21'/&gt;
        &lt;sibling id='3' value='10'/&gt;
      &lt;/distances&gt;
    &lt;/cell&gt;
  &lt;/numa&gt;
  ...
&lt;/cpu&gt;
...</pre>

    <p>
      Describing distances between NUMA cells is currently only supported
1833
      by Xen and QEMU. If no <code>distances</code> are given to describe
1834 1835
      the SLIT data between different cells, it will default to a scheme
      using 10 for local and 20 for remote distances.
1836 1837
    </p>

1838
    <h3><a id="elementsEvents">Events configuration</a></h3>
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    <p>
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      It is sometimes necessary to override the default actions taken
1842 1843
      on various events. Not all hypervisors support all events and actions.
      The actions may be taken as a result of calls to libvirt APIs
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      <a href="html/libvirt-libvirt-domain.html#virDomainReboot">
        <code>virDomainReboot</code>
      </a>,
      <a href="html/libvirt-libvirt-domain.html#virDomainShutdown">
        <code>virDomainShutdown</code>
      </a>,
      or
      <a href="html/libvirt-libvirt-domain.html#virDomainShutdownFlags">
        <code>virDomainShutdownFlags</code>
      </a>.
1854 1855
      Using <code>virsh reboot</code> or <code>virsh shutdown</code> would
      also trigger the event.
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    </p>

1858
<pre>
1859 1860 1861 1862 1863 1864
...
&lt;on_poweroff&gt;destroy&lt;/on_poweroff&gt;
&lt;on_reboot&gt;restart&lt;/on_reboot&gt;
&lt;on_crash&gt;restart&lt;/on_crash&gt;
&lt;on_lockfailure&gt;poweroff&lt;/on_lockfailure&gt;
...</pre>
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    <p>
      The following collections of elements allow the actions to be
      specified when a guest OS triggers a lifecycle operation. A
      common use case is to force a reboot to be treated as a poweroff
      when doing the initial OS installation. This allows the VM to be
      re-configured for the first post-install bootup.
    </p>
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    <dl>
      <dt><code>on_poweroff</code></dt>
      <dd>The content of this element specifies the action to take when
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        the guest requests a poweroff.</dd>
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      <dt><code>on_reboot</code></dt>
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      <dd>The content of this element specifies the action to take when
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        the guest requests a reboot.</dd>
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      <dt><code>on_crash</code></dt>
D
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      <dd>The content of this element specifies the action to take when
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        the guest crashes.</dd>
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    </dl>

    <p>
      Each of these states allow for the same four possible actions.
    </p>

    <dl>
      <dt><code>destroy</code></dt>
      <dd>The domain will be terminated completely and all resources
1892
        released.</dd>
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      <dt><code>restart</code></dt>
1894 1895
      <dd>The domain will be terminated and then restarted with
        the same configuration.</dd>
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      <dt><code>preserve</code></dt>
1897
      <dd>The domain will be terminated and its resource preserved
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        to allow analysis.</dd>
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      <dt><code>rename-restart</code></dt>
1900 1901
      <dd>The domain will be terminated and then restarted with
        a new name.</dd>
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    </dl>

1904
    <p>
1905 1906 1907 1908 1909 1910 1911 1912 1913 1914
    QEMU/KVM supports the <code>on_poweroff</code> and <code>on_reboot</code>
    events handling the <code>destroy</code> and <code>restart</code> actions.
    The <code>preserve</code> action for an <code>on_reboot</code> event
    is treated as a <code>destroy</code> and the <code>rename-restart</code>
    action for an <code>on_poweroff</code> event is treated as a
    <code>restart</code> event.
    </p>

    <p>
      The <code>on_crash</code> event supports these additional
1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927
      actions <span class="since">since 0.8.4</span>.
    </p>

    <dl>
      <dt><code>coredump-destroy</code></dt>
      <dd>The crashed domain's core will be dumped, and then the
        domain will be terminated completely and all resources
        released</dd>
      <dt><code>coredump-restart</code></dt>
      <dd>The crashed domain's core will be dumped, and then the
        domain will be restarted with the same configuration</dd>
    </dl>

1928 1929 1930 1931 1932 1933 1934
    <p>
      <span class="since">Since 3.9.0</span>, the lifecycle events can
      be configured via the
      <a href="html/libvirt-libvirt-domain.html#virDomainSetLifecycleAction">
        <code>virDomainSetLifecycleAction</code></a> API.
    </p>

1935 1936
    <p>
      The <code>on_lockfailure</code> element (<span class="since">since
1937
      1.0.0</span>) may be used to configure what action should be
1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955
      taken when a lock manager loses resource locks. The following
      actions are recognized by libvirt, although not all of them need
      to be supported by individual lock managers. When no action is
      specified, each lock manager will take its default action.
    </p>
    <dl>
      <dt><code>poweroff</code></dt>
      <dd>The domain will be forcefully powered off.</dd>
      <dt><code>restart</code></dt>
      <dd>The domain will be powered off and started up again to
        reacquire its locks.</dd>
      <dt><code>pause</code></dt>
      <dd>The domain will be paused so that it can be manually resumed
        when lock issues are solved.</dd>
      <dt><code>ignore</code></dt>
      <dd>Keep the domain running as if nothing happened.</dd>
    </dl>

1956
    <h3><a id="elementsPowerManagement">Power Management</a></h3>
1957 1958 1959 1960 1961 1962 1963 1964

    <p>
      <span class="since">Since 0.10.2</span> it is possible to
      forcibly enable or disable BIOS advertisements to the guest
      OS. (NB: Only qemu driver support)
    </p>

<pre>
1965 1966 1967 1968 1969 1970
...
&lt;pm&gt;
  &lt;suspend-to-disk enabled='no'/&gt;
  &lt;suspend-to-mem enabled='yes'/&gt;
&lt;/pm&gt;
...</pre>
1971 1972 1973 1974

    <dl>
      <dt><code>pm</code></dt>
      <dd>These elements enable ('yes') or disable ('no') BIOS support
1975
        for S3 (suspend-to-mem) and S4 (suspend-to-disk) ACPI sleep
1976
        states. If nothing is specified, then the hypervisor will be
1977 1978 1979 1980 1981
        left with its default value.<br/>
        Note: This setting cannot prevent the guest OS from performing
        a suspend as the guest OS itself can choose to circumvent the
        unavailability of the sleep states (e.g. S4 by turning off
        completely).</dd>
1982 1983
    </dl>

1984
    <h3><a id="elementsFeatures">Hypervisor features</a></h3>
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    <p>
      Hypervisors may allow certain CPU / machine features to be
      toggled on/off.
    </p>

1991
<pre>
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
...
&lt;features&gt;
  &lt;pae/&gt;
  &lt;acpi/&gt;
  &lt;apic/&gt;
  &lt;hap/&gt;
  &lt;privnet/&gt;
  &lt;hyperv&gt;
    &lt;relaxed state='on'/&gt;
    &lt;vapic state='on'/&gt;
    &lt;spinlocks state='on' retries='4096'/&gt;
    &lt;vpindex state='on'/&gt;
    &lt;runtime state='on'/&gt;
    &lt;synic state='on'/&gt;
    &lt;reset state='on'/&gt;
    &lt;vendor_id state='on' value='KVM Hv'/&gt;
2008
    &lt;frequencies state='on'/&gt;
2009
    &lt;reenlightenment state='on'/&gt;
2010
    &lt;tlbflush state='on'/&gt;
2011
    &lt;ipi state='on'/&gt;
2012
    &lt;evmcs state='on'/&gt;
2013
    &lt;msrs unknown='ignore'/&gt;
2014 2015 2016 2017 2018 2019
  &lt;/hyperv&gt;
  &lt;kvm&gt;
    &lt;hidden state='on'/&gt;
  &lt;/kvm&gt;
  &lt;pvspinlock state='on'/&gt;
  &lt;gic version='2'/&gt;
2020
  &lt;ioapic driver='qemu'/&gt;
2021 2022 2023
  &lt;hpt resizing='required'&gt;
    &lt;maxpagesize unit='MiB'&gt;16&lt;/maxpagesize&gt;
  &lt;/hpt&gt;
2024
  &lt;vmcoreinfo state='on'/&gt;
2025 2026 2027
  &lt;smm state='on'&gt;
    &lt;tseg unit='MiB'&gt;48&lt;/tseg&gt;
  &lt;/smm&gt;
2028
  &lt;htm state='on'/&gt;
2029 2030
&lt;/features&gt;
...</pre>
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    <p>
      All features are listed within the <code>features</code>
      element, omitting a togglable feature tag turns it off.
      The available features can be found by asking
2036 2037
      for the <a href="formatcaps.html">capabilities XML</a> and
      <a href="formatdomaincaps.html">domain capabilities XML</a>,
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      but a common set for fully virtualized domains are:
    </p>

    <dl>
      <dt><code>pae</code></dt>
      <dd>Physical address extension mode allows 32-bit guests
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        to address more than 4 GB of memory.</dd>
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      <dt><code>acpi</code></dt>
      <dd>ACPI is useful for power management, for example, with
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        KVM guests it is required for graceful shutdown to work.
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      </dd>
2049 2050
      <dt><code>apic</code></dt>
      <dd>APIC allows the use of programmable IRQ
2051 2052 2053
      management. <span class="since">Since 0.10.2 (QEMU only)</span> there is
      an optional attribute <code>eoi</code> with values <code>on</code>
      and <code>off</code> which toggles the availability of EOI (End of
2054 2055
      Interrupt) for the guest.
      </dd>
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      <dt><code>hap</code></dt>
2057 2058 2059 2060
      <dd>Depending on the <code>state</code> attribute (values <code>on</code>,
        <code>off</code>) enable or disable use of Hardware Assisted Paging.
        The default is <code>on</code> if the hypervisor detects availability
        of Hardware Assisted Paging.
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      </dd>
2062 2063 2064 2065
      <dt><code>viridian</code></dt>
      <dd>Enable Viridian hypervisor extensions for paravirtualizing
        guest operating systems
      </dd>
2066 2067 2068 2069 2070 2071
      <dt><code>privnet</code></dt>
      <dd>Always create a private network namespace. This is
        automatically set if any interface devices are defined.
        This feature is only relevant for container based
        virtualization drivers, such as LXC.
      </dd>
2072 2073 2074 2075 2076 2077 2078 2079
      <dt><code>hyperv</code></dt>
      <dd>Enable various features improving behavior of guests
        running Microsoft Windows.
      <table class="top_table">
        <tr>
          <th>Feature</th>
          <th>Description</th>
          <th>Value</th>
2080
          <th>Since</th>
2081 2082 2083
        </tr>
        <tr>
          <td>relaxed</td>
2084
          <td>Relax constraints on timers</td>
2085
          <td>on, off</td>
2086
          <td><span class="since">1.0.0 (QEMU 2.0)</span></td>
2087 2088 2089 2090 2091
        </tr>
        <tr>
          <td>vapic</td>
          <td>Enable virtual APIC</td>
          <td>on, off</td>
2092
          <td><span class="since">1.1.0 (QEMU 2.0)</span></td>
2093 2094 2095 2096 2097
        </tr>
        <tr>
          <td>spinlocks</td>
          <td>Enable spinlock support</td>
          <td>on, off; retries - at least 4095</td>
2098
          <td><span class="since">1.1.0 (QEMU 2.0)</span></td>
2099
        </tr>
2100 2101 2102
        <tr>
          <td>vpindex</td>
          <td>Virtual processor index</td>
2103
          <td>on, off</td>
2104 2105 2106 2107 2108
          <td><span class="since">1.3.3 (QEMU 2.5)</span></td>
        </tr>
        <tr>
          <td>runtime</td>
          <td>Processor time spent on running guest code and on behalf of guest code</td>
2109
          <td>on, off</td>
2110 2111 2112 2113 2114
          <td><span class="since">1.3.3 (QEMU 2.5)</span></td>
        </tr>
        <tr>
          <td>synic</td>
          <td>Enable Synthetic Interrupt Controller (SyNIC)</td>
2115
          <td>on, off</td>
2116
          <td><span class="since">1.3.3 (QEMU 2.6)</span></td>
2117 2118 2119 2120
        </tr>
        <tr>
          <td>stimer</td>
          <td>Enable SyNIC timers</td>
2121
          <td>on, off</td>
2122
          <td><span class="since">1.3.3 (QEMU 2.6)</span></td>
2123 2124 2125 2126
        </tr>
        <tr>
          <td>reset</td>
          <td>Enable hypervisor reset</td>
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          <td>on, off</td>
2128 2129 2130 2131 2132 2133 2134 2135
          <td><span class="since">1.3.3 (QEMU 2.5)</span></td>
        </tr>
        <tr>
          <td>vendor_id</td>
          <td>Set hypervisor vendor id</td>
          <td>on, off; value - string, up to 12 characters</td>
          <td><span class="since">1.3.3 (QEMU 2.5)</span></td>
        </tr>
2136 2137 2138
        <tr>
          <td>frequencies</td>
          <td>Expose frequency MSRs</td>
2139
          <td>on, off</td>
2140 2141
          <td><span class="since">4.7.0 (QEMU 2.12)</span></td>
        </tr>
2142 2143 2144
        <tr>
          <td>reenlightenment</td>
          <td>Enable re-enlightenment notification on migration</td>
2145
          <td>on, off</td>
2146 2147
          <td><span class="since">4.7.0 (QEMU 3.0)</span></td>
        </tr>
2148 2149 2150
        <tr>
          <td>tlbflush</td>
          <td>Enable PV TLB flush support</td>
2151
          <td>on, off</td>
2152 2153
          <td><span class="since">4.7.0 (QEMU 3.0)</span></td>
        </tr>
2154 2155 2156 2157 2158 2159
        <tr>
          <td>ipi</td>
          <td>Enable PV IPI support</td>
          <td>on, off</td>
          <td><span class="since">4.10.0 (QEMU 3.1)</span></td>
        </tr>
2160 2161 2162 2163 2164 2165
        <tr>
          <td>evmcs</td>
          <td>Enable Enlightened VMCS</td>
          <td>on, off</td>
          <td><span class="since">4.10.0 (QEMU 3.1)</span></td>
        </tr>
2166 2167
      </table>
      </dd>
2168 2169 2170 2171 2172 2173
      <dt><code>pvspinlock</code></dt>
      <dd>Notify the guest that the host supports paravirtual spinlocks
          for example by exposing the pvticketlocks mechanism. This feature
          can be explicitly disabled by using <code>state='off'</code>
          attribute.
      </dd>
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      <dt><code>kvm</code></dt>
      <dd>Various features to change the behavior of the KVM hypervisor.
      <table class="top_table">
        <tr>
          <th>Feature</th>
          <th>Description</th>
          <th>Value</th>
          <th>Since</th>
        </tr>
        <tr>
          <td>hidden</td>
          <td>Hide the KVM hypervisor from standard MSR based discovery</td>
          <td>on, off</td>
2187
          <td><span class="since">1.2.8 (QEMU 2.1.0)</span></td>
2188 2189 2190
        </tr>
      </table>
      </dd>
2191 2192 2193 2194 2195 2196
      <dt><code>pmu</code></dt>
      <dd>Depending on the <code>state</code> attribute (values <code>on</code>,
        <code>off</code>, default <code>on</code>) enable or disable the
        performance monitoring unit for the guest.
        <span class="since">Since 1.2.12</span>
      </dd>
2197 2198 2199
      <dt><code>vmport</code></dt>
      <dd>Depending on the <code>state</code> attribute (values <code>on</code>,
        <code>off</code>, default <code>on</code>) enable or disable
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        the emulation of VMware IO port, for vmmouse etc.
2201 2202
        <span class="since">Since 1.2.16</span>
      </dd>
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      <dt><code>gic</code></dt>
      <dd>Enable for architectures using a General Interrupt
          Controller instead of APIC in order to handle interrupts.
          For example, the 'aarch64' architecture uses
          <code>gic</code> instead of <code>apic</code>. The optional
          attribute <code>version</code> specifies the GIC version;
2209 2210 2211
          however, it may not be supported by all hypervisors. Accepted
          values are <code>2</code>, <code>3</code> and <code>host</code>.
          <span class="since">Since 1.2.16</span>
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      </dd>
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      <dt><code>smm</code></dt>
2214 2215 2216
      <dd>
        <p>
          Depending on the <code>state</code> attribute (values <code>on</code>,
2217 2218
          <code>off</code>, default <code>on</code>) enable or disable
          System Management Mode.
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          <span class="since">Since 2.1.0</span>
2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237
        </p><p> Optional sub-element <code>tseg</code> can be used to specify
          the amount of memory dedicated to SMM's extended TSEG. That offers a
          fourth option size apart from the existing ones (1 MiB, 2 MiB and 8
          MiB) that the guest OS (or rather loader) can choose from. The size
          can be specified as a value of that element, optional attribute
          <code>unit</code> can be used to specify the unit of the
          aforementioned value (defaults to 'MiB').  If set to 0 the extended
          size is not advertised and only the default ones (see above) are
          available.
        </p><p>
          <b>If the VM is booting you should leave this option alone, unless you
          are very certain you know what you are doing.</b>
        </p><p>
          This value is configurable due to the fact that the calculation cannot
          be done right with the guarantee that it will work correctly.  In
          QEMU, the user-configurable extended TSEG feature was unavailable up
          to and including <code>pc-q35-2.9</code>. Starting with
          <code>pc-q35-2.10</code> the feature is available, with default size
2238
          16 MiB.  That should suffice for up to roughly 272 vCPUs, 5 GiB guest
2239
          RAM in total, no hotplug memory range, and 32 GiB of 64-bit PCI MMIO
2240
          aperture.  Or for 48 vCPUs, with 1TB of guest RAM, no hotplug DIMM
2241 2242 2243
          range, and 32GB of 64-bit PCI MMIO aperture. The values may also vary
          based on the loader the VM is using.
        </p><p>
2244
          Additional size might be needed for significantly higher vCPU counts
2245 2246 2247 2248 2249 2250 2251 2252 2253
          or increased address space (that can be memory, maxMemory, 64-bit PCI
          MMIO aperture size; roughly 8 MiB of TSEG per 1 TiB of address space)
          which can also be rounded up.
        </p><p>
          Due to the nature of this setting being similar to "how much RAM
          should the guest have" users are advised to either consult the
          documentation of the guest OS or loader (if there is any), or test
          this by trial-and-error changing the value until the VM boots
          successfully.  Yet another guiding value for users might be the fact
2254
          that 48 MiB should be enough for pretty large guests (240 vCPUs and
2255 2256 2257 2258 2259 2260 2261 2262
          4TB guest RAM), but it is on purpose not set as default as 48 MiB of
          unavailable RAM might be too much for small guests (e.g. with 512 MiB
          of RAM).
        </p><p>
          See <a href="#elementsMemoryAllocation">Memory Allocation</a>
          for more details about the <code>unit</code> attribute.
          <span class="since">Since 4.5.0</span> (QEMU only)
        </p>
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      </dd>
2264 2265 2266 2267 2268 2269 2270 2271
      <dt><code>ioapic</code></dt>
      <dd>Tune the I/O APIC. Possible values for the
          <code>driver</code> attribute are:
          <code>kvm</code> (default for KVM domains)
          and <code>qemu</code> which puts I/O APIC in userspace
          which is also known as a split I/O APIC mode.
          <span class="since">Since 3.4.0</span> (QEMU/KVM only)
      </dd>
2272 2273 2274 2275 2276 2277 2278 2279 2280
      <dt><code>hpt</code></dt>
      <dd>Configure the HPT (Hash Page Table) of a pSeries guest. Possible
          values for the <code>resizing</code> attribute are
          <code>enabled</code>, which causes HPT resizing to be enabled if
          both the guest and the host support it; <code>disabled</code>, which
          causes HPT resizing to be disabled regardless of guest and host
          support; and <code>required</code>, which prevents the guest from
          starting unless both the guest and the host support HPT resizing. If
          the attribute is not defined, the hypervisor default will be used.
2281 2282 2283 2284 2285 2286
          <span class="since">Since 3.10.0</span> (QEMU/KVM only).

          <p>The optional <code>maxpagesize</code> subelement can be used to
          limit the usable page size for HPT guests. Common values are 64 KiB,
          16 MiB and 16 GiB; when not specified, the hypervisor default will
          be used. <span class="since">Since 4.5.0</span> (QEMU/KVM only).</p>
2287
      </dd>
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      <dt><code>vmcoreinfo</code></dt>
      <dd>Enable QEMU vmcoreinfo device to let the guest kernel save debug
2290
          details. <span class="since">Since 4.4.0</span> (QEMU only)
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      </dd>
2292 2293 2294 2295 2296 2297 2298
      <dt><code>htm</code></dt>
      <dd>Configure HTM (Hardware Transational Memory) availability for
          pSeries guests. Possible values for the <code>state</code> attribute
          are <code>on</code> and <code>off</code>. If the attribute is not
          defined, the hypervisor default will be used.
          <span class="since">Since 4.6.0</span> (QEMU/KVM only)
      </dd>
2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310
      <dt><code>nested-hv</code></dt>
      <dd>Configure nested HV availability for pSeries guests. This needs to
          be enabled from the host (L0) in order to be effective; having HV
          support in the (L1) guest is very desiderable if it's planned to
          run nested (L2) guests inside it, because it will result in those
          nested guests having much better performance than they would when
          using KVM PR or TCG.
          Possible values for the <code>state</code> attribute are
          <code>on</code> and <code>off</code>. If the attribute is not
          defined, the hypervisor default will be used.
          <span class="since">Since 4.10.0</span> (QEMU/KVM only)
      </dd>
2311 2312 2313 2314 2315 2316 2317 2318 2319
      <dt><code>msrs</code></dt>
      <dd>Some guests might require ignoring unknown
          Model Specific Registers (MSRs) reads and writes. It's possible
          to switch this by setting <code>unknown</code> attribute
          of <code>msrs</code> to <code>ignore</code>. If the attribute is
          not defined, or set to <code>fault</code>, unknown reads and writes
          will not be ignored.
          <span class="since">Since 5.1.0</span> (bhyve only)
      </dd>
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    </dl>

2322
    <h3><a id="elementsTime">Time keeping</a></h3>
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    <p>
      The guest clock is typically initialized from the host clock.
      Most operating systems expect the hardware clock to be kept
      in UTC, and this is the default. Windows, however, expects
      it to be in so called 'localtime'.
    </p>

2331
<pre>
2332 2333 2334 2335 2336 2337 2338 2339
...
&lt;clock offset='localtime'&gt;
  &lt;timer name='rtc' tickpolicy='catchup' track='guest'&gt;
    &lt;catchup threshold='123' slew='120' limit='10000'/&gt;
  &lt;/timer&gt;
  &lt;timer name='pit' tickpolicy='delay'/&gt;
&lt;/clock&gt;
...</pre>
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    <dl>
      <dt><code>clock</code></dt>
2343
      <dd>
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        <p>The <code>offset</code> attribute takes four possible
          values, allowing fine grained control over how the guest
          clock is synchronized to the host. NB, not all hypervisors
          support all modes.</p>
        <dl>
          <dt><code>utc</code></dt>
          <dd>
            The guest clock will always be synchronized to UTC when
2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362
            booted.
            <span class="since">Since 0.9.11</span> 'utc' mode can be converted
            to 'variable' mode, which can be controlled by using the
            <code>adjustment</code> attribute. If the value is 'reset', the
            conversion is never done (not all hypervisors can
            synchronize to UTC on each boot; use of 'reset' will cause
            an error on those hypervisors). A numeric value
            forces the conversion to 'variable' mode using the value as the
            initial adjustment. The default <code>adjustment</code> is
            hypervisor specific.
          </dd>
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          <dt><code>localtime</code></dt>
          <dd>
            The guest clock will be synchronized to the host's configured
            timezone when booted, if any.
2367 2368
            <span class="since">Since 0.9.11,</span> the <code>adjustment</code>
            attribute behaves the same as in 'utc' mode.
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          </dd>
          <dt><code>timezone</code></dt>
          <dd>
            The guest clock will be synchronized to the requested timezone
            using the <code>timezone</code> attribute.
            <span class="since">Since 0.7.7</span>
          </dd>
          <dt><code>variable</code></dt>
          <dd>
            The guest clock will have an arbitrary offset applied
2379 2380
            relative to UTC or localtime, depending on the <code>basis</code>
            attribute. The delta relative to UTC (or localtime) is specified
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            in seconds, using the <code>adjustment</code> attribute.
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            The guest is free to adjust the RTC over time and expect
2383 2384 2385
            that it will be honored at next reboot. This is in
            contrast to 'utc' and 'localtime' mode (with the optional
            attribute adjustment='reset'), where the RTC adjustments are
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            lost at each reboot. <span class="since">Since 0.7.7</span>
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            <span class="since">Since 0.9.11</span> the <code>basis</code>
            attribute can be either 'utc' (default) or 'localtime'.
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          </dd>
        </dl>
        <p>
          A <code>clock</code> may have zero or more
2393
          <code>timer</code> sub-elements. <span class="since">Since
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          0.8.0</span>
        </p>
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      </dd>
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      <dt><code>timer</code></dt>
      <dd>
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        <p>
          Each timer element requires a <code>name</code> attribute,
          and has other optional attributes that depend on
          the <code>name</code> specified.  Various hypervisors
          support different combinations of attributes.
        </p>
        <dl>
          <dt><code>name</code></dt>
          <dd>
            The <code>name</code> attribute selects which timer is
2409 2410 2411
            being modified, and can be one of
            "platform" (currently unsupported),
            "hpet" (libxl, xen, qemu), "kvmclock" (qemu),
2412 2413 2414 2415 2416 2417 2418
            "pit" (qemu), "rtc" (qemu), "tsc" (libxl) or "hypervclock"
            (qemu - <span class="since">since 1.2.2</span>).

            The <code>hypervclock</code> timer adds support for the
            reference time counter and the reference page for iTSC
            feature for guests running the Microsoft Windows
            operating system.
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          </dd>
          <dt><code>track</code></dt>
          <dd>
            The <code>track</code> attribute specifies what the timer
            tracks, and can be "boot", "guest", or "wall".
            Only valid for <code>name="rtc"</code>
            or <code>name="platform"</code>.
          </dd>
          <dt><code>tickpolicy</code></dt>
          <dd>
2429 2430
            <p>
            The <code>tickpolicy</code> attribute determines what
2431
            happens when QEMU misses a deadline for injecting a
2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454
            tick to the guest:
            </p>
            <dl>
              <dt><code>delay</code></dt>
              <dd>Continue to deliver ticks at the normal rate.
                The guest time will be delayed due to the late
                tick</dd>
              <dt><code>catchup</code></dt>
              <dd>Deliver ticks at a higher rate to catch up
                with the missed tick. The guest time should
                not be delayed once catchup is complete.</dd>
              <dt><code>merge</code></dt>
              <dd>Merge the missed tick(s) into one tick and
                inject. The guest time may be delayed, depending
                on how the OS reacts to the merging of ticks</dd>
              <dt><code>discard</code></dt>
              <dd>Throw away the missed tick(s) and continue
                with future injection normally. The guest time
                may be delayed, unless the OS has explicit
                handling of lost ticks</dd>
            </dl>
            <p>If the policy is "catchup", there can be further details in
            the <code>catchup</code> sub-element.</p>
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            <dl>
              <dt><code>catchup</code></dt>
              <dd>
                The <code>catchup</code> element has three optional
                attributes, each a positive integer.  The attributes
                are <code>threshold</code>, <code>slew</code>,
                and <code>limit</code>.
              </dd>
            </dl>
2464 2465 2466
            <p>
              Note that hypervisors are not required to support all policies across all time sources
            </p>
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          </dd>
          <dt><code>frequency</code></dt>
          <dd>
            The <code>frequency</code> attribute is an unsigned
            integer specifying the frequency at
            which <code>name="tsc"</code> runs.
          </dd>
          <dt><code>mode</code></dt>
          <dd>
            The <code>mode</code> attribute controls how
            the <code>name="tsc"</code> timer is managed, and can be
            "auto", "native", "emulate", "paravirt", or "smpsafe".
            Other timers are always emulated.
          </dd>
          <dt><code>present</code></dt>
          <dd>
            The <code>present</code> attribute can be "yes" or "no" to
            specify whether a particular timer is available to the guest.
          </dd>
        </dl>
2487
      </dd>
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    </dl>

2490
    <h3><a id="elementsPerf">Performance monitoring events</a></h3>
2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501

    <p>
      Some platforms allow monitoring of performance of the virtual machine and
      the code executed inside. To enable the performance monitoring events
      you can either specify them in the <code>perf</code> element or enable
      them via <code>virDomainSetPerfEvents</code> API. The performance values
      are then retrieved using the virConnectGetAllDomainStats API.
      <span class="since">Since 2.0.0</span>
    </p>

<pre>
2502 2503 2504 2505 2506 2507 2508 2509 2510
...
&lt;perf&gt;
  &lt;event name='cmt' enabled='yes'/&gt;
  &lt;event name='mbmt' enabled='no'/&gt;
  &lt;event name='mbml' enabled='yes'/&gt;
  &lt;event name='cpu_cycles' enabled='no'/&gt;
  &lt;event name='instructions' enabled='yes'/&gt;
  &lt;event name='cache_references' enabled='no'/&gt;
  &lt;event name='cache_misses' enabled='no'/&gt;
2511
  &lt;event name='branch_instructions' enabled='no'/&gt;
2512
  &lt;event name='branch_misses' enabled='no'/&gt;
2513
  &lt;event name='bus_cycles' enabled='no'/&gt;
2514
  &lt;event name='stalled_cycles_frontend' enabled='no'/&gt;
2515
  &lt;event name='stalled_cycles_backend' enabled='no'/&gt;
2516
  &lt;event name='ref_cpu_cycles' enabled='no'/&gt;
2517
  &lt;event name='cpu_clock' enabled='no'/&gt;
2518
  &lt;event name='task_clock' enabled='no'/&gt;
2519
  &lt;event name='page_faults' enabled='no'/&gt;
2520
  &lt;event name='context_switches' enabled='no'/&gt;
2521
  &lt;event name='cpu_migrations' enabled='no'/&gt;
2522
  &lt;event name='page_faults_min' enabled='no'/&gt;
2523
  &lt;event name='page_faults_maj' enabled='no'/&gt;
2524
  &lt;event name='alignment_faults' enabled='no'/&gt;
2525
  &lt;event name='emulation_faults' enabled='no'/&gt;
2526 2527
&lt;/perf&gt;
...
2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550
</pre>

  <table class="top_table">
    <tr>
      <th>event name</th>
      <th>Description</th>
      <th>stats parameter name</th>
    </tr>
    <tr>
      <td><code>cmt</code></td>
      <td>usage of l3 cache in bytes by applications running on the platform</td>
      <td><code>perf.cmt</code></td>
    </tr>
    <tr>
      <td><code>mbmt</code></td>
      <td>total system bandwidth from one level of cache</td>
      <td><code>perf.mbmt</code></td>
    </tr>
    <tr>
      <td><code>mbml</code></td>
      <td>bandwidth of memory traffic for a memory controller</td>
      <td><code>perf.mbml</code></td>
    </tr>
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    <tr>
      <td><code>cpu_cycles</code></td>
2553
      <td>the count of CPU cycles (total/elapsed)</td>
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      <td><code>perf.cpu_cycles</code></td>
    </tr>
    <tr>
      <td><code>instructions</code></td>
      <td>the count of instructions by applications running on the platform</td>
      <td><code>perf.instructions</code></td>
    </tr>
    <tr>
      <td><code>cache_references</code></td>
      <td>the count of cache hits by applications running on the platform</td>
      <td><code>perf.cache_references</code></td>
    </tr>
    <tr>
      <td><code>cache_misses</code></td>
      <td>the count of cache misses by applications running on the platform</td>
      <td><code>perf.cache_misses</code></td>
    </tr>
2571 2572 2573 2574 2575
    <tr>
      <td><code>branch_instructions</code></td>
      <td>the count of branch instructions by applications running on the platform</td>
      <td><code>perf.branch_instructions</code></td>
    </tr>
2576 2577 2578 2579 2580
    <tr>
      <td><code>branch_misses</code></td>
      <td>the count of branch misses by applications running on the platform</td>
      <td><code>perf.branch_misses</code></td>
    </tr>
2581 2582 2583 2584 2585
    <tr>
      <td><code>bus_cycles</code></td>
      <td>the count of bus cycles by applications running on the platform</td>
      <td><code>perf.bus_cycles</code></td>
    </tr>
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    <tr>
      <td><code>stalled_cycles_frontend</code></td>
2588
      <td>the count of stalled CPU cycles in the frontend of the instruction
2589 2590 2591
          processor pipeline by applications running on the platform</td>
      <td><code>perf.stalled_cycles_frontend</code></td>
    </tr>
2592 2593
    <tr>
      <td><code>stalled_cycles_backend</code></td>
2594
      <td>the count of stalled CPU cycles in the backend of the instruction
2595 2596 2597
          processor pipeline by applications running on the platform</td>
      <td><code>perf.stalled_cycles_backend</code></td>
    </tr>
2598 2599
    <tr>
      <td><code>ref_cpu_cycles</code></td>
2600
      <td>the count of total CPU cycles not affected by CPU frequency scaling
2601 2602 2603
         by applications running on the platform</td>
      <td><code>perf.ref_cpu_cycles</code></td>
    </tr>
2604 2605
    <tr>
      <td><code>cpu_clock</code></td>
2606
      <td>the count of CPU clock time, as measured by a monotonic
2607 2608 2609 2610
          high-resolution per-CPU timer, by applications running on
          the platform</td>
      <td><code>perf.cpu_clock</code></td>
    </tr>
2611 2612 2613 2614 2615 2616 2617
    <tr>
      <td><code>task_clock</code></td>
      <td>the count of task clock time, as measured by a monotonic
          high-resolution CPU timer, specific to the task that
          is run by applications running on the platform</td>
      <td><code>perf.task_clock</code></td>
    </tr>
2618 2619 2620 2621 2622 2623 2624
    <tr>
      <td><code>page_faults</code></td>
      <td>the count of page faults by applications running on the
          platform. This includes minor, major, invalid and other
          types of page faults</td>
      <td><code>perf.page_faults</code></td>
    </tr>
2625 2626 2627 2628 2629 2630
    <tr>
      <td><code>context_switches</code></td>
      <td>the count of context switches by applications running on
          the platform</td>
      <td><code>perf.context_switches</code></td>
    </tr>
2631 2632
    <tr>
      <td><code>cpu_migrations</code></td>
2633
      <td>the count of CPU migrations, that is, where the process
2634 2635 2636 2637
          moved from one logical processor to another, by
          applications running on the platform</td>
      <td><code>perf.cpu_migrations</code></td>
    </tr>
2638 2639 2640 2641 2642 2643 2644 2645
    <tr>
      <td><code>page_faults_min</code></td>
      <td>the count of minor page faults, that is, where the
          page was present in the page cache, and therefore
          the fault avoided loading it from storage, by
          applications running on the platform</td>
      <td><code>perf.page_faults_min</code></td>
    </tr>
2646 2647 2648 2649 2650 2651 2652 2653
    <tr>
      <td><code>page_faults_maj</code></td>
      <td>the count of major page faults, that is, where the
          page was not present in the page cache, and
          therefore had to be fetched from storage, by
          applications running on the platform</td>
      <td><code>perf.page_faults_maj</code></td>
    </tr>
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    <tr>
      <td><code>alignment_faults</code></td>
      <td>the count of alignment faults, that is when
          the load or store is not aligned properly, by
          applications running on the platform</td>
      <td><code>perf.alignment_faults</code></td>
    </tr>
2661 2662 2663 2664 2665 2666 2667 2668
    <tr>
      <td><code>emulation_faults</code></td>
      <td>the count of emulation faults, that is when
          the kernel traps on unimplemented instrucions
          and emulates them for user space, by
          applications running on the platform</td>
      <td><code>perf.emulation_faults</code></td>
    </tr>
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  </table>

2671
    <h3><a id="elementsDevices">Devices</a></h3>
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    <p>
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      The final set of XML elements are all used to describe devices
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      provided to the guest domain. All devices occur as children
      of the main <code>devices</code> element.
      <span class="since">Since 0.1.3</span>
    </p>

2680
<pre>
2681 2682 2683 2684 2685
...
&lt;devices&gt;
  &lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&gt;
&lt;/devices&gt;
...</pre>
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    <dl>
2688
      <dt><a id="elementEmulator"><code>emulator</code></a></dt>
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      <dd>
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        The contents of the <code>emulator</code> element specify
        the fully qualified path to the device model emulator binary.
        The <a href="formatcaps.html">capabilities XML</a> specifies
        the recommended default emulator to use for each particular
        domain type / architecture combination.
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      </dd>
    </dl>

M
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    <p>
      To help users identifying devices they care about, every
      device can have direct child <code>alias</code> element
      which then has <code>name</code> attribute where users can
      store identifier for the device. The identifier has to have
      "ua-" prefix and must be unique within the domain. Additionally, the
      identifier must consist only of the following characters:
      <code>[a-zA-Z0-9_-]</code>.
      <span class="since">Since 3.9.0</span>
    </p>

<pre>
&lt;devices&gt;
  &lt;disk type='file'&gt;
    &lt;alias name='ua-myDisk'/&gt;
  &lt;/disk&gt;
  &lt;interface type='network' trustGuestRxFilters='yes'&gt;
    &lt;alias name='ua-myNIC'/&gt;
  &lt;/interface&gt;
  ...
&lt;/devices&gt;
</pre>

2721
    <h4><a id="elementsDisks">Hard drives, floppy disks, CDROMs</a></h4>
D
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    <p>
      Any device that looks like a disk, be it a floppy, harddisk,
      cdrom, or paravirtualized driver is specified via the <code>disk</code>
      element.
    </p>

2729
<pre>
2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744
...
&lt;devices&gt;
  &lt;disk type='file' snapshot='external'&gt;
    &lt;driver name="tap" type="aio" cache="default"/&gt;
    &lt;source file='/var/lib/xen/images/fv0' startupPolicy='optional'&gt;
      &lt;seclabel relabel='no'/&gt;
    &lt;/source&gt;
    &lt;target dev='hda' bus='ide'/&gt;
    &lt;iotune&gt;
      &lt;total_bytes_sec&gt;10000000&lt;/total_bytes_sec&gt;
      &lt;read_iops_sec&gt;400000&lt;/read_iops_sec&gt;
      &lt;write_iops_sec&gt;100000&lt;/write_iops_sec&gt;
    &lt;/iotune&gt;
    &lt;boot order='2'/&gt;
    &lt;encryption type='...'&gt;
M
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      ...
2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768
    &lt;/encryption&gt;
    &lt;shareable/&gt;
    &lt;serial&gt;
      ...
    &lt;/serial&gt;
  &lt;/disk&gt;
    ...
  &lt;disk type='network'&gt;
    &lt;driver name="qemu" type="raw" io="threads" ioeventfd="on" event_idx="off"/&gt;
    &lt;source protocol="sheepdog" name="image_name"&gt;
      &lt;host name="hostname" port="7000"/&gt;
    &lt;/source&gt;
    &lt;target dev="hdb" bus="ide"/&gt;
    &lt;boot order='1'/&gt;
    &lt;transient/&gt;
    &lt;address type='drive' controller='0' bus='1' unit='0'/&gt;
  &lt;/disk&gt;
  &lt;disk type='network'&gt;
    &lt;driver name="qemu" type="raw"/&gt;
    &lt;source protocol="rbd" name="image_name2"&gt;
      &lt;host name="hostname" port="7000"/&gt;
      &lt;snapshot name="snapname"/&gt;
      &lt;config file="/path/to/file"/&gt;
2769 2770 2771
      &lt;auth username='myuser'&gt;
        &lt;secret type='ceph' usage='mypassid'/&gt;
      &lt;/auth&gt;
2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821
    &lt;/source&gt;
    &lt;target dev="hdc" bus="ide"/&gt;
  &lt;/disk&gt;
  &lt;disk type='block' device='cdrom'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;target dev='hdd' bus='ide' tray='open'/&gt;
    &lt;readonly/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='cdrom'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol="http" name="url_path"&gt;
      &lt;host name="hostname" port="80"/&gt;
    &lt;/source&gt;
    &lt;target dev='hde' bus='ide' tray='open'/&gt;
    &lt;readonly/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='cdrom'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol="https" name="url_path"&gt;
      &lt;host name="hostname" port="443"/&gt;
    &lt;/source&gt;
    &lt;target dev='hdf' bus='ide' tray='open'/&gt;
    &lt;readonly/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='cdrom'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol="ftp" name="url_path"&gt;
      &lt;host name="hostname" port="21"/&gt;
    &lt;/source&gt;
    &lt;target dev='hdg' bus='ide' tray='open'/&gt;
    &lt;readonly/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='cdrom'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol="ftps" name="url_path"&gt;
      &lt;host name="hostname" port="990"/&gt;
    &lt;/source&gt;
    &lt;target dev='hdh' bus='ide' tray='open'/&gt;
    &lt;readonly/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='cdrom'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol="tftp" name="url_path"&gt;
      &lt;host name="hostname" port="69"/&gt;
    &lt;/source&gt;
    &lt;target dev='hdi' bus='ide' tray='open'/&gt;
    &lt;readonly/&gt;
  &lt;/disk&gt;
  &lt;disk type='block' device='lun'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
2822
    &lt;source dev='/dev/sda'&gt;
2823
      &lt;reservations managed='no'&gt;
2824 2825
        &lt;source type='unix' path='/path/to/qemu-pr-helper' mode='client'/&gt;
      &lt;/reservations&gt;
2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844
    &lt;target dev='sda' bus='scsi'/&gt;
    &lt;address type='drive' controller='0' bus='0' target='3' unit='0'/&gt;
  &lt;/disk&gt;
  &lt;disk type='block' device='disk'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source dev='/dev/sda'/&gt;
    &lt;geometry cyls='16383' heads='16' secs='63' trans='lba'/&gt;
    &lt;blockio logical_block_size='512' physical_block_size='4096'/&gt;
    &lt;target dev='hdj' bus='ide'/&gt;
  &lt;/disk&gt;
  &lt;disk type='volume' device='disk'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source pool='blk-pool0' volume='blk-pool0-vol0'/&gt;
    &lt;target dev='hdk' bus='ide'/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='disk'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/2'&gt;
      &lt;host name='example.com' port='3260'/&gt;
2845 2846 2847
      &lt;auth username='myuser'&gt;
        &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
2848 2849 2850 2851 2852 2853 2854
    &lt;/source&gt;
    &lt;target dev='vda' bus='virtio'/&gt;
  &lt;/disk&gt;
  &lt;disk type='network' device='lun'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/1'&gt;
      &lt;host name='example.com' port='3260'/&gt;
2855 2856 2857
      &lt;auth username='myuser'&gt;
        &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
2858 2859 2860
    &lt;/source&gt;
    &lt;target dev='sdb' bus='scsi'/&gt;
  &lt;/disk&gt;
2861 2862 2863 2864 2865 2866 2867 2868 2869 2870
  &lt;disk type='network' device='lun'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/0'&gt;
      &lt;host name='example.com' port='3260'/&gt;
      &lt;initiator&gt;
        &lt;iqn name='iqn.2013-07.com.example:client'/&gt;
      &lt;/initiator&gt;
    &lt;/source&gt;
    &lt;target dev='sdb' bus='scsi'/&gt;
  &lt;/disk&gt;
2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881
  &lt;disk type='volume' device='disk'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source pool='iscsi-pool' volume='unit:0:0:1' mode='host'/&gt;
    &lt;target dev='vdb' bus='virtio'/&gt;
  &lt;/disk&gt;
  &lt;disk type='volume' device='disk'&gt;
    &lt;driver name='qemu' type='raw'/&gt;
    &lt;source pool='iscsi-pool' volume='unit:0:0:2' mode='direct'/&gt;
    &lt;target dev='vdc' bus='virtio'/&gt;
  &lt;/disk&gt;
  &lt;disk type='file' device='disk'&gt;
L
Lin Ma 已提交
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    &lt;driver name='qemu' type='qcow2' queues='4'/&gt;
2883 2884 2885 2886 2887 2888 2889 2890
    &lt;source file='/var/lib/libvirt/images/domain.qcow'/&gt;
    &lt;backingStore type='file'&gt;
      &lt;format type='qcow2'/&gt;
      &lt;source file='/var/lib/libvirt/images/snapshot.qcow'/&gt;
      &lt;backingStore type='block'&gt;
        &lt;format type='raw'/&gt;
        &lt;source dev='/dev/mapper/base'/&gt;
        &lt;backingStore/&gt;
2891
      &lt;/backingStore&gt;
2892 2893 2894 2895 2896
    &lt;/backingStore&gt;
    &lt;target dev='vdd' bus='virtio'/&gt;
  &lt;/disk&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
2897 2898 2899

    <dl>
      <dt><code>disk</code></dt>
2900 2901
      <dd>The <code>disk</code> element is the main container for
      describing disks and supports the following attributes:
2902
        <dl>
2903
          <dt><code>type</code></dt>
2904 2905 2906 2907 2908 2909
            <dd>
            Valid values are "file", "block",
            "dir" (<span class="since">since 0.7.5</span>),
            "network" (<span class="since">since 0.8.7</span>), or
            "volume" (<span class="since">since 1.0.5</span>)
            and refer to the underlying source for the disk.
2910
            <span class="since">Since 0.0.3</span>
2911
            </dd>
2912
          <dt><code>device</code></dt>
2913 2914 2915 2916 2917 2918
            <dd>
            Indicates how the disk is to be exposed to the guest OS. Possible
            values for this attribute are "floppy", "disk", "cdrom", and "lun",
            defaulting to "disk".
            <p>
            Using "lun" (<span class="since">since 0.9.10</span>) is only
2919 2920
            valid when the <code>type</code> is "block" or "network" for
            <code>protocol='iscsi'</code> or when the <code>type</code>
2921
            is "volume" when using an iSCSI source <code>pool</code>
2922 2923 2924
            for <code>mode</code> "host" or as an
            <a href="http://wiki.libvirt.org/page/NPIV_in_libvirt">NPIV</a>
            virtual Host Bus Adapter (vHBA) using a Fibre Channel storage pool.
2925
            Configured in this manner, the LUN behaves identically to "disk",
2926 2927 2928 2929 2930 2931
            except that generic SCSI commands from the guest are accepted
            and passed through to the physical device. Also note that
            device='lun' will only be recognized for actual raw devices,
            but never for individual partitions or LVM partitions (in those
            cases, the kernel will reject the generic SCSI commands, making
            it identical to device='disk').
2932
            <span class="since">Since 0.1.4</span>
2933 2934
            </p>
            </dd>
2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945
          <dt><code>model</code></dt>
            <dd>
            Indicates the emulated device model of the disk. Typically
            this is indicated solely by the <code>bus</code> property but
            for <code>bus</code> "virtio" the model can be specified further
            with "virtio-transitional", "virtio-non-transitional", or
            "virtio". See
            <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
            for more details.
            <span class="since">Since 5.2.0</span>
            </dd>
2946
          <dt><code>rawio</code></dt>
2947
            <dd>
2948
            Indicates whether the disk needs rawio capability. Valid
2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959
            settings are "yes" or "no" (default is "no"). If any one disk
            in a domain has rawio='yes', rawio capability will be enabled
            for all disks in the domain (because, in the case of QEMU, this
            capability can only be set on a per-process basis). This attribute
            is only valid when device is "lun". NB, <code>rawio</code> intends
            to confine the capability per-device, however, current QEMU
            implementation gives the domain process broader capability
            than that (per-process basis, affects all the domain disks).
            To confine the capability as much as possible for QEMU driver
            as this stage, <code>sgio</code> is recommended, it's more
            secure than <code>rawio</code>.
2960
            <span class="since">Since 0.9.10</span>
2961
            </dd>
2962
          <dt><code>sgio</code></dt>
2963
            <dd>
2964 2965 2966 2967
            If supported by the hypervisor and OS, indicates whether
            unprivileged SG_IO commands are filtered for the disk. Valid
            settings are "filtered" or "unfiltered" where the default is
            "filtered". Only available when the <code>device</code> is 'lun'.
2968
            <span class="since">Since 1.0.2</span>
2969
            </dd>
2970
          <dt><code>snapshot</code></dt>
2971 2972
            <dd>
            Indicates the default behavior of the disk during disk snapshots:
2973 2974 2975 2976 2977 2978 2979
            "<code>internal</code>" requires a file format such as qcow2 that
            can store both the snapshot and the data changes since the snapshot;
            "<code>external</code>" will separate the snapshot from the live
            data; and "<code>no</code>" means the disk will not participate in
            snapshots. Read-only disks default to "<code>no</code>", while the
            default for other disks depends on the hypervisor's capabilities.
            Some hypervisors allow a per-snapshot choice as well, during
2980
            <a href="formatsnapshot.html">domain snapshot creation</a>.
2981 2982
            Not all snapshot modes are supported; for example, enabling
            snapshots with a transient disk generally does not make sense.
2983
            <span class="since">Since 0.9.5</span>
2984 2985 2986
            </dd>
        </dl>
      </dd>
D
Daniel P. Berrange 已提交
2987
      <dt><code>source</code></dt>
2988 2989 2990
      <dd>Representation of the disk <code>source</code> depends on the
      disk <code>type</code> attribute value as follows:
          <dl>
2991
            <dt><code>file</code></dt>
2992 2993 2994
              <dd>
              The <code>file</code> attribute specifies the fully-qualified
              path to the file holding the disk.
2995
              <span class="since">Since 0.0.3</span>
2996
              </dd>
2997
            <dt><code>block</code></dt>
2998
              <dd>
2999 3000
              The <code>dev</code> attribute specifies the fully-qualified path
              to the host device to serve as the disk.
3001
              <span class="since">Since 0.0.3</span>
3002
              </dd>
3003
            <dt><code>dir</code></dt>
3004 3005 3006
              <dd>
              The <code>dir</code> attribute specifies the fully-qualified path
              to the directory to use as the disk.
3007
              <span class="since">Since 0.7.5</span>
3008
              </dd>
3009
            <dt><code>network</code></dt>
3010 3011 3012
              <dd>
              The <code>protocol</code> attribute specifies the protocol to
              access to the requested image. Possible values are "nbd",
3013 3014 3015 3016 3017 3018 3019
              "iscsi", "rbd", "sheepdog", "gluster" or "vxhs".

              <p>If the <code>protocol</code> attribute is "rbd", "sheepdog",
              "gluster", or "vxhs", an additional attribute <code>name</code>
              is mandatory to specify which volume/image will be used.
              </p>

3020 3021 3022 3023 3024 3025 3026
              <p>For "nbd", the <code>name</code> attribute is optional. TLS
              transport for NBD can be enabled by setting the <code>tls</code>
              attribute to <code>yes</code>. For the QEMU hypervisor, usage of
              a TLS environment can also be globally controlled on the host by
              the <code>nbd_tls</code> and <code>nbd_tls_x509_cert_dir</code> in
              /etc/libvirt/qemu.conf.
              ('tls' <span class="since">Since 4.5.0</span>)
3027 3028 3029 3030 3031
              </p>

              <p>For "iscsi" (<span class="since">since 1.0.4</span>), the
              <code>name</code> attribute may include a logical unit number,
              separated from the target's name by a slash (e.g.,
3032 3033
              <code>iqn.2013-07.com.example:iscsi-pool/1</code>). If not
              specified, the default LUN is zero.
3034 3035
              </p>

3036
              <p>For "vxhs" (<span class="since">since 3.8.0</span>), the
3037
              <code>name</code> is the UUID of the volume, assigned by the
3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050
              HyperScale server. Additionally, an optional attribute
              <code>tls</code> (QEMU only) can be used to control whether a
              VxHS block device would utilize a hypervisor configured TLS
              X.509 certificate environment in order to encrypt the data
              channel. For the QEMU hypervisor, usage of a TLS environment can
              also be globally controlled on the host by the
              <code>vxhs_tls</code> and <code>vxhs_tls_x509_cert_dir</code> or
              <code>default_tls_x509_cert_dir</code> settings in the file
              /etc/libvirt/qemu.conf. If <code>vxhs_tls</code> is enabled,
              then unless the domain <code>tls</code> attribute is set to "no",
              libvirt will use the host configured TLS environment. If the
              <code>tls</code> attribute is set to "yes", then regardless of
              the qemu.conf setting, TLS authentication will be attempted.
3051
              </p>
3052
              <span class="since">Since 0.8.7</span>
3053
              </dd>
3054
            <dt><code>volume</code></dt>
3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080
              <dd>
              The underlying disk source is represented by attributes
              <code>pool</code> and <code>volume</code>. Attribute
              <code>pool</code> specifies the name of the
              <a href="formatstorage.html">storage pool</a> (managed
              by libvirt) where the disk source resides. Attribute
              <code>volume</code> specifies the name of storage volume (managed
              by libvirt) used as the disk source. The value for the
              <code>volume</code> attribute will be the output from the "Name"
              column of a <code>virsh vol-list [pool-name]</code> command.
              <p>
              Use the attribute <code>mode</code>
              (<span class="since">since 1.1.1</span>) to indicate how to
              represent the LUN as the disk source. Valid values are
              "direct" and "host". If <code>mode</code> is not specified,
              the default is to use "host".

              Using "direct" as the <code>mode</code> value indicates to use
              the <a href="formatstorage.html">storage pool's</a>
              <code>source</code> element <code>host</code> attribute as
              the disk source to generate the libiscsi URI (e.g.
              'file=iscsi://example.com:3260/iqn.2013-07.com.example:iscsi-pool/1').

              Using "host" as the <code>mode</code> value indicates to use the
              LUN's path as it shows up on host (e.g.
              'file=/dev/disk/by-path/ip-example.com:3260-iscsi-iqn.2013-07.com.example:iscsi-pool-lun-1').
3081 3082 3083

              Using a LUN from an iSCSI source pool provides the same
              features as a <code>disk</code> configured using
3084
              <code>type</code> 'block' or 'network' and <code>device</code>
3085
              of 'lun' with respect to how the LUN is presented to and
3086
              may be used by the guest.
3087

3088
              <span class="since">Since 1.0.5</span>
3089 3090 3091 3092
              </p>
              </dd>
          </dl>
        With "file", "block", and "volume", one or more optional
3093
        sub-elements <code>seclabel</code>, <a href="#seclabel">described
3094 3095
        below</a> (and <span class="since">since 0.9.9</span>), can be
        used to override the domain security labeling policy for just
3096 3097
        that source file. (NB, for "volume" type disk, <code>seclabel</code>
        is only valid when the specified storage volume is of 'file' or
3098 3099
        'block' type).
        <p>
3100 3101 3102 3103 3104
        The <code>source</code> element may also have the <code>index</code>
        attribute with same semantics the <a href='#elementsDiskBackingStoreIndex'>
        <code>index</code></a> attribute of <code>backingStore</code>
        </p>
        <p>
3105
        The <code>source</code> element may contain the following sub elements:
3106
        </p>
3107 3108 3109 3110 3111

        <dl>
          <dt><code>host</code></dt>
          <dd>
            <p>
3112 3113 3114 3115
            When the disk <code>type</code> is "network", the <code>source</code>
            may have zero or more <code>host</code> sub-elements used to
            specify the hosts to connect.

3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144
            The <code>host</code> element supports 4 attributes, viz.  "name",
            "port", "transport" and "socket", which specify the hostname,
            the port number, transport type and path to socket, respectively.
            The meaning of this element and the number of the elements depend
            on the protocol attribute.
            </p>
            <table class="top_table">
              <tr>
                <th> Protocol </th>
                <th> Meaning </th>
                <th> Number of hosts </th>
                <th> Default port </th>
              </tr>
              <tr>
                <td> nbd </td>
                <td> a server running nbd-server </td>
                <td> only one </td>
                <td> 10809 </td>
              </tr>
              <tr>
                <td> iscsi </td>
                <td> an iSCSI server </td>
                <td> only one </td>
                <td> 3260 </td>
              </tr>
              <tr>
                <td> rbd </td>
                <td> monitor servers of RBD </td>
                <td> one or more </td>
3145
                <td> librados default </td>
3146 3147 3148 3149 3150 3151 3152 3153 3154 3155
              </tr>
              <tr>
                <td> sheepdog </td>
                <td> one of the sheepdog servers (default is localhost:7000) </td>
                <td> zero or one </td>
                <td> 7000 </td>
              </tr>
              <tr>
                <td> gluster </td>
                <td> a server running glusterd daemon </td>
3156
                <td> one or more (<span class="since">Since 2.1.0</span>), just one prior to that </td>
3157 3158
                <td> 24007 </td>
              </tr>
3159 3160 3161 3162 3163 3164
              <tr>
                <td> vxhs </td>
                <td> a server running Veritas HyperScale daemon </td>
                <td> only one </td>
                <td> 9999 </td>
              </tr>
3165 3166 3167 3168 3169 3170 3171 3172 3173
            </table>
            <p>
            gluster supports "tcp", "rdma", "unix" as valid values for the
            transport attribute.  nbd supports "tcp" and "unix".  Others only
            support "tcp".  If nothing is specified, "tcp" is assumed. If the
            transport is "unix", the socket attribute specifies the path to an
            AF_UNIX socket.
            </p>
          </dd>
3174 3175 3176 3177 3178 3179 3180
          <dt><code>snapshot</code></dt>
          <dd>
            The <code>name</code> attribute of <code>snapshot</code> element can
            optionally specify an internal snapshot name to be used as the
            source for storage protocols.
            Supported for 'rbd' <span class="since">since 1.2.11 (QEMU only).</span>
          </dd>
3181 3182 3183 3184 3185 3186 3187 3188
          <dt><code>config</code></dt>
          <dd>
            The <code>file</code> attribute for the <code>config</code> element
            provides a fully qualified path to a configuration file to be
            provided as a parameter to the client of a networked storage
            protocol. Supported for 'rbd' <span class="since">since 1.2.11
            (QEMU only).</span>
          </dd>
3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210
          <dt><code>auth</code></dt>
          <dd><span class="since">Since libvirt 3.9.0</span>, the
            <code>auth</code> element is supported for a disk
            <code>type</code> "network" that is using a <code>source</code>
            element with the <code>protocol</code> attributes "rbd" or "iscsi".
            If present, the <code>auth</code> element provides the
            authentication credentials needed to access the source.  It
            includes a mandatory attribute <code>username</code>, which
            identifies the username to use during authentication, as well
            as a sub-element <code>secret</code> with mandatory
            attribute <code>type</code>, to tie back to
            a <a href="formatsecret.html">libvirt secret object</a> that
            holds the actual password or other credentials (the domain XML
            intentionally does not expose the password, only the reference
            to the object that does manage the password).
            Known secret types are "ceph" for Ceph RBD network sources and
            "iscsi" for CHAP authentication of iSCSI targets.
            Both will require either a <code>uuid</code> attribute
            with the UUID of the secret object or a <code>usage</code>
            attribute matching the key that was specified in the
            secret object.
          </dd>
3211
          <dt><code>encryption</code></dt>
3212 3213 3214 3215 3216 3217 3218
          <dd><span class="since">Since libvirt 3.9.0</span>, the
            <code>encryption</code> can be a sub-element of the
            <code>source</code> element for encrypted storage sources.
            If present, specifies how the storage source is encrypted
            See the
            <a href="formatstorageencryption.html">Storage Encryption</a>
            page for more information.
3219 3220 3221 3222
            <p/>
            Note that the 'qcow' format of encryption is broken and thus is no
            longer supported for use with disk images.
            (<span class="since">Since libvirt 4.5.0</span>)
3223
          </dd>
3224 3225 3226 3227
          <dt><code>reservations</code></dt>
          <dd><span class="since">Since libvirt 4.4.0</span>, the
            <code>reservations</code> can be a sub-element of the
            <code>source</code> element for storage sources (QEMU driver only).
3228
            If present it enables persistent reservations for SCSI
3229
            based disks. The element has one mandatory attribute
3230 3231 3232 3233 3234 3235 3236 3237 3238
            <code>managed</code> with accepted values <code>yes</code> and
            <code>no</code>. If <code>managed</code> is enabled libvirt prepares
            and manages any resources needed. When the persistent reservations
            are unmanaged, then the hypervisor acts as a client and the path to
            the server socket must be provided in the child element
            <code>source</code>, which currently accepts only the following
            attributes:
            <code>type</code> with one value <code>unix</code>,
            <code>path</code> path to the socket, and
3239
            finally <code>mode</code> which accepts one value
3240
            <code>client</code> specifying the role of hypervisor.
3241 3242 3243
            It's recommended to allow libvirt manage the persistent
            reservations.
          </dd>
3244 3245 3246 3247 3248 3249 3250 3251 3252
          <dt><code>initiator</code></dt>
          <dd><span class="since">Since libvirt 4.7.0</span>, the
            <code>initiator</code> element is supported for a disk
            <code>type</code> "network" that is using a <code>source</code>
            element with the <code>protocol</code> attribute "iscsi".
            If present, the <code>initiator</code> element provides the
            initiator IQN needed to access the source via mandatory
            attribute <code>name</code>.
          </dd>
3253 3254
        </dl>

3255
        <p>
3256
        For a "file" or "volume" disk type which represents a cdrom or floppy
3257 3258
        (the <code>device</code> attribute), it is possible to define
        policy what to do with the disk if the source file is not accessible.
3259 3260
        (NB, <code>startupPolicy</code> is not valid for "volume" disk unless
         the specified storage volume is of "file" type). This is done by the
3261 3262
        <code>startupPolicy</code> attribute
        (<span class="since">since 0.9.7</span>),
3263
        accepting these values:
3264
        </p>
3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279
        <table class="top_table">
          <tr>
            <td> mandatory </td>
            <td> fail if missing for any reason (the default) </td>
          </tr>
          <tr>
            <td> requisite </td>
            <td> fail if missing on boot up,
                 drop if missing on migrate/restore/revert </td>
          </tr>
          <tr>
            <td> optional </td>
            <td> drop if missing at any start attempt </td>
          </tr>
        </table>
3280 3281 3282 3283 3284 3285 3286
        <p>
        <span class="since">Since 1.1.2</span> the <code>startupPolicy</code>
        is extended to support hard disks besides cdrom and floppy. On guest
        cold bootup, if a certain disk is not accessible or its disk chain is
        broken, with startupPolicy 'optional' the guest will drop this disk.
        This feature doesn't support migration currently.
        </p>
3287
        </dd>
3288 3289
      <dt><code>backingStore</code></dt>
      <dd>
D
Deepak Shetty 已提交
3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303
        This element describes the backing store used by the disk
        specified by sibling <code>source</code> element. It is
        currently ignored on input and only used for output to
        describe the detected backing chains of running
        domains <span class="since">since 1.2.4</span> (although a
        future version of libvirt may start accepting chains on input,
        or output information for offline domains). An
        empty <code>backingStore</code> element means the sibling
        source is self-contained and is not based on any backing
        store. For backing chain information to be accurate, the
        backing format must be correctly specified in the metadata of
        each file of the chain (files created by libvirt satisfy this
        property, but using existing external files for snapshot or
        block copy operations requires the end user to pre-create the
3304
        file correctly). The following attributes are
D
Deepak Shetty 已提交
3305
        supported in <code>backingStore</code>:
3306
        <dl>
3307
          <dt><code>type</code></dt>
3308 3309 3310 3311 3312
          <dd>
            The <code>type</code> attribute represents the type of disk used
            by the backing store, see disk type attribute above for more
            details and possible values.
          </dd>
3313
          <dt><code><a id="elementsDiskBackingStoreIndex">index</a></code></dt>
3314 3315 3316 3317 3318 3319 3320 3321
          <dd>
            This attribute is only valid in output (and ignored on input) and
            it can be used to refer to a specific part of the disk chain when
            doing block operations (such as via the
            <code>virDomainBlockRebase</code> API). For example,
            <code>vda[2]</code> refers to the backing store with
            <code>index='2'</code> of the disk with <code>vda</code> target.
          </dd>
3322 3323 3324 3325
        </dl>
        Moreover, <code>backingStore</code> supports the following sub-elements:
        <dl>
          <dt><code>format</code></dt>
3326 3327 3328 3329 3330
          <dd>
            The <code>format</code> element contains <code>type</code>
            attribute which specifies the internal format of the backing
            store, such as <code>raw</code> or <code>qcow2</code>.
          </dd>
3331
          <dt><code>source</code></dt>
3332 3333 3334 3335 3336 3337
          <dd>
            This element has the same structure as the <code>source</code>
            element in <code>disk</code>. It specifies which file, device,
            or network location contains the data of the described backing
            store.
          </dd>
3338
          <dt><code>backingStore</code></dt>
3339 3340 3341 3342 3343 3344 3345
          <dd>
            If the backing store is not self-contained, the next element
            in the chain is described by nested <code>backingStore</code>
            element.
          </dd>
        </dl>
      </dd>
3346 3347
      <dt><code>mirror</code></dt>
      <dd>
E
Eric Blake 已提交
3348 3349 3350 3351
        This element is present if the hypervisor has started a
        long-running block job operation, where the mirror location in
        the <code>source</code> sub-element will eventually have the
        same contents as the source, and with the file format in the
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        sub-element <code>format</code> (which might differ from the
        format of the source).  The details of the <code>source</code>
        sub-element are determined by the <code>type</code> attribute
        of the mirror, similar to what is done for the
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        overall <code>disk</code> device element. The <code>job</code>
        attribute mentions which API started the operation ("copy" for
        the <code>virDomainBlockRebase</code> API, or "active-commit"
        for the <code>virDomainBlockCommit</code>
        API), <span class="since">since 1.2.7</span>.  The
3361 3362 3363 3364 3365 3366
        attribute <code>ready</code>, if present, tracks progress of
        the job: <code>yes</code> if the disk is known to be ready to
        pivot, or, <span class="since">since
        1.2.7</span>, <code>abort</code> or <code>pivot</code> if the
        job is in the process of completing.  If <code>ready</code> is
        not present, the disk is probably still
3367
        copying.  For now, this element only valid in output; it is
3368 3369 3370 3371 3372 3373 3374
        ignored on input.  The <code>source</code> sub-element exists
        for all two-phase jobs <span class="since">since 1.2.6</span>.
        Older libvirt supported only block copy to a
        file, <span class="since">since 0.9.12</span>; for
        compatibility with older clients, such jobs include redundant
        information in the attributes <code>file</code>
        and <code>format</code> in the <code>mirror</code> element.
3375
      </dd>
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      <dt><code>target</code></dt>
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      <dd>The <code>target</code> element controls the bus / device
        under which the disk is exposed to the guest
        OS. The <code>dev</code> attribute indicates the "logical"
        device name. The actual device name specified is not
        guaranteed to map to the device name in the guest OS. Treat it
        as a device ordering hint.  The optional <code>bus</code>
        attribute specifies the type of disk device to emulate;
        possible values are driver specific, with typical values being
3385 3386
        "ide", "scsi", "virtio", "xen", "usb", "sata", or
        "sd" <span class="since">"sd" since 1.1.2</span>. If omitted, the bus
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        type is inferred from the style of the device name (e.g. a device named
        'sda' will typically be exported using a SCSI bus). The optional
3389 3390 3391 3392
        attribute <code>tray</code> indicates the tray status of the
        removable disks (i.e. CDROM or Floppy disk), the value can be either
        "open" or "closed", defaults to "closed". NB, the value of
        <code>tray</code> could be updated while the domain is running.
3393 3394 3395 3396
        The optional attribute <code>removable</code> sets the
        removable flag for USB disks, and its value can be either "on"
        or "off", defaulting to "off". <span class="since">Since
        0.0.3; <code>bus</code> attribute since 0.4.3;
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        <code>tray</code> attribute since 0.9.11; "usb" attribute value since
3398 3399
        after 0.4.4; "sata" attribute value since 0.9.7; "removable" attribute
        value since 1.1.3</span>
3400
      </dd>
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      <dt><code>iotune</code></dt>
      <dd>The optional <code>iotune</code> element provides the
        ability to provide additional per-device I/O tuning, with
        values that can vary for each device (contrast this to
        the <a href="#elementsBlockTuning"><code>&lt;blkiotune&gt;</code></a>
        element, which applies globally to the domain).  Currently,
        the only tuning available is Block I/O throttling for qemu.
        This element has optional sub-elements; any sub-element not
        specified or given with a value of 0 implies no
        limit.  <span class="since">Since 0.9.8</span>
        <dl>
          <dt><code>total_bytes_sec</code></dt>
          <dd>The optional <code>total_bytes_sec</code> element is the
            total throughput limit in bytes per second.  This cannot
            appear with <code>read_bytes_sec</code>
            or <code>write_bytes_sec</code>.</dd>
          <dt><code>read_bytes_sec</code></dt>
          <dd>The optional <code>read_bytes_sec</code> element is the
            read throughput limit in bytes per second.</dd>
          <dt><code>write_bytes_sec</code></dt>
          <dd>The optional <code>write_bytes_sec</code> element is the
            write throughput limit in bytes per second.</dd>
          <dt><code>total_iops_sec</code></dt>
          <dd>The optional <code>total_iops_sec</code> element is the
            total I/O operations per second.  This cannot
            appear with <code>read_iops_sec</code>
            or <code>write_iops_sec</code>.</dd>
          <dt><code>read_iops_sec</code></dt>
          <dd>The optional <code>read_iops_sec</code> element is the
            read I/O operations per second.</dd>
          <dt><code>write_iops_sec</code></dt>
          <dd>The optional <code>write_iops_sec</code> element is the
            write I/O operations per second.</dd>
3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457
          <dt><code>total_bytes_sec_max</code></dt>
          <dd>The optional <code>total_bytes_sec_max</code> element is the
            maximum total throughput limit in bytes per second.  This cannot
            appear with <code>read_bytes_sec_max</code>
            or <code>write_bytes_sec_max</code>.</dd>
          <dt><code>read_bytes_sec_max</code></dt>
          <dd>The optional <code>read_bytes_sec_max</code> element is the
            maximum read throughput limit in bytes per second.</dd>
          <dt><code>write_bytes_sec_max</code></dt>
          <dd>The optional <code>write_bytes_sec_max</code> element is the
            maximum write throughput limit in bytes per second.</dd>
          <dt><code>total_iops_sec_max</code></dt>
          <dd>The optional <code>total_iops_sec_max</code> element is the
            maximum total I/O operations per second.  This cannot
            appear with <code>read_iops_sec_max</code>
            or <code>write_iops_sec_max</code>.</dd>
          <dt><code>read_iops_sec_max</code></dt>
          <dd>The optional <code>read_iops_sec_max</code> element is the
            maximum read I/O operations per second.</dd>
          <dt><code>write_iops_sec_max</code></dt>
          <dd>The optional <code>write_iops_sec_max</code> element is the
            maximum write I/O operations per second.</dd>
          <dt><code>size_iops_sec</code></dt>
          <dd>The optional <code>size_iops_sec</code> element is the
3458 3459 3460 3461 3462
            size of I/O operations per second.
          <p>
            <span class="since">Throughput limits since 1.2.11 and QEMU 1.7</span>
          </p>
          </dd>
3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473
          <dt><code>group_name</code></dt>
          <dd>The optional <code>group_name</code> provides the cability
            to share I/O throttling quota between multiple drives. This
            prevents end-users from circumventing a hosting provider's
            throttling policy by splitting 1 large drive in N small drives
            and getting N times the normal throttling quota. Any name may
            be used.
          <p>
            <span class="since">group_name since 3.0.0 and QEMU 2.4</span>
          </p>
          </dd>
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          <dt><code>total_bytes_sec_max_length</code></dt>
          <dd>The optional <code>total_bytes_sec_max_length</code>
            element is the maximum duration in seconds for the
            <code>total_bytes_sec_max</code> burst period. Only valid
            when the <code>total_bytes_sec_max</code> is set.</dd>
          <dt><code>read_bytes_sec_max_length</code></dt>
          <dd>The optional <code>read_bytes_sec_max_length</code>
            element is the maximum duration in seconds for the
            <code>read_bytes_sec_max</code> burst period. Only valid
            when the <code>read_bytes_sec_max</code> is set.</dd>
          <dt><code>write_bytes_sec_max</code></dt>
          <dd>The optional <code>write_bytes_sec_max_length</code>
            element is the maximum duration in seconds for the
            <code>write_bytes_sec_max</code> burst period. Only valid
            when the <code>write_bytes_sec_max</code> is set.</dd>
          <dt><code>total_iops_sec_max_length</code></dt>
          <dd>The optional <code>total_iops_sec_max_length</code>
            element is the maximum duration in seconds for the
            <code>total_iops_sec_max</code> burst period. Only valid
            when the <code>total_iops_sec_max</code> is set.</dd>
          <dt><code>read_iops_sec_max_length</code></dt>
          <dd>The optional <code>read_iops_sec_max_length</code>
            element is the maximum duration in seconds for the
            <code>read_iops_sec_max</code> burst period. Only valid
            when the <code>read_iops_sec_max</code> is set.</dd>
          <dt><code>write_iops_sec_max</code></dt>
          <dd>The optional <code>write_iops_sec_max_length</code>
            element is the maximum duration in seconds for the
            <code>write_iops_sec_max</code> burst period. Only valid
            when the <code>write_iops_sec_max</code> is set.
          <p>
            <span class="since">Throughput length since 2.4.0 and QEMU 2.6</span>
          </p>
          </dd>
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        </dl>
3509
      </dd>
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      <dt><code>driver</code></dt>
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      <dd>
        The optional driver element allows specifying further details
        related to the hypervisor driver used to provide the disk.
3514
        <span class="since">Since 0.1.8</span>
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        <ul>
          <li>
            If the hypervisor supports multiple backend drivers, then
            the <code>name</code> attribute selects the primary
            backend driver name, while the optional <code>type</code>
            attribute provides the sub-type.  For example, xen
            supports a name of "tap", "tap2", "phy", or "file", with a
            type of "aio", while qemu only supports a name of "qemu",
            but multiple types including "raw", "bochs", "qcow2", and
            "qed".
          </li>
          <li>
            The optional <code>cache</code> attribute controls the
            cache mechanism, possible values are "default", "none",
3529 3530 3531 3532 3533 3534 3535 3536 3537
            "writethrough", "writeback", "directsync" (like
            "writethrough", but it bypasses the host page cache) and
            "unsafe" (host may cache all disk io, and sync requests from
            guest are ignored).
            <span class="since">
              Since 0.6.0,
              "directsync" since 0.9.5,
              "unsafe" since 0.9.7
            </span>
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          </li>
          <li>
            The optional <code>error_policy</code> attribute controls
3541 3542 3543
            how the hypervisor will behave on a disk read or write
            error, possible values are "stop", "report", "ignore", and
            "enospace".<span class="since">Since 0.8.0, "report" since
3544 3545
            0.9.7</span> The default is left to the discretion of the
            hypervisor. There is also an
3546 3547
            optional <code>rerror_policy</code> that controls behavior
            for read errors only. <span class="since">Since
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            0.9.7</span>. If no rerror_policy is given, error_policy
3549 3550 3551 3552 3553
            is used for both read and write errors. If rerror_policy
            is given, it overrides the <code>error_policy</code> for
            read errors. Also note that "enospace" is not a valid
            policy for read errors, so if <code>error_policy</code> is
            set to "enospace" and no <code>rerror_policy</code> is
3554
            given, the read error policy will be left at its default.
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          </li>
          <li>
            The optional <code>io</code> attribute controls specific
            policies on I/O; qemu guests support "threads" and
3559
            "native". <span class="since">Since 0.8.8</span>
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          </li>
3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574
          <li>
            The optional <code>ioeventfd</code> attribute allows users to
            set <a href='https://patchwork.kernel.org/patch/43390/'>
            domain I/O asynchronous handling</a> for disk device.
            The default is left to the discretion of the hypervisor.
            Accepted values are "on" and "off". Enabling this allows
            qemu to execute VM while a separate thread handles I/O.
            Typically guests experiencing high system CPU utilization
            during I/O will benefit from this. On the other hand,
            on overloaded host it could increase guest I/O latency.
            <span class="since">Since 0.9.3 (QEMU and KVM only)</span>
            <b>In general you should leave this option alone, unless you
            are very certain you know what you are doing.</b>
          </li>
3575 3576 3577 3578
          <li>
            The optional <code>event_idx</code> attribute controls
            some aspects of device event processing. The value can be
            either 'on' or 'off' - if it is on, it will reduce the
3579
            number of interrupts and exits for the guest. The default
3580 3581 3582 3583 3584 3585 3586 3587
            is determined by QEMU; usually if the feature is
            supported, default is on. In case there is a situation
            where this behavior is suboptimal, this attribute provides
            a way to force the feature off.
            <span class="since">Since 0.9.5 (QEMU and KVM only)</span>
            <b>In general you should leave this option alone, unless you
            are very certain you know what you are doing.</b>
          </li>
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          <li>
            The optional <code>copy_on_read</code> attribute controls
3590
            whether to copy read backing file into the image file. The
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            value can be either "on" or "off".
            Copy-on-read avoids accessing the same backing file sectors
            repeatedly and is useful when the backing file is over a slow
            network. By default copy-on-read is off.
            <span class='since'>Since 0.9.10 (QEMU and KVM only)</span>
          </li>
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          <li>
            The optional <code>discard</code> attribute controls whether
3599
            discard requests (also known as "trim" or "unmap") are
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            ignored or passed to the filesystem. The value can be either
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            "unmap" (allow the discard request to be passed) or "ignore"
            (ignore the discard request).
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            <span class='since'>Since 1.0.6 (QEMU and KVM only)</span>
          </li>
3605 3606 3607 3608 3609 3610 3611 3612 3613 3614
          <li>
            The optional <code>detect_zeroes</code> attribute controls whether
            to detect zero write requests.  The value can be "off", "on" or
            "unmap".  First two values turn the detection off and on,
            respectively.  The third value ("unmap") turns the detection on
            and additionally tries to discard such areas from the image based
            on the value of <code>discard</code> above (it will act as "on"
            if <code>discard</code> is set to "ignore").  NB enabling the
            detection is a compute intensive operation, but can save file
            space and/or time on slow media.
3615
            <span class='since'>Since 2.0.0</span>
3616
          </li>
3617 3618 3619 3620
          <li>
            The optional <code>iothread</code> attribute assigns the
            disk to an IOThread as defined by the range for the domain
            <a href="#elementsIOThreadsAllocation"><code>iothreads</code></a>
3621 3622 3623 3624 3625
            value. Multiple disks may be assigned to the same IOThread and
            are numbered from 1 to the domain iothreads value. Available
            for a disk device <code>target</code> configured to use "virtio"
            <code>bus</code> and "pci" or "ccw" <code>address</code> types.
            <span class='since'>Since 1.2.8 (QEMU 2.1)</span>
3626
          </li>
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          <li>
            The optional <code>queues</code> attribute specifies the number of
            virt queues for virtio-blk. (<span class="since">Since 3.9.0</span>)
          </li>
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          <li>
          For virtio disks,
          <a href="#elementsVirtio">Virtio-specific options</a> can also be
          set. (<span class="since">Since 3.5.0</span>)
          </li>
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        </ul>
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      </dd>
3638 3639 3640 3641 3642 3643
      <dt><code>backenddomain</code></dt>
      <dd>The optional <code>backenddomain</code> element allows specifying a
          backend domain (aka driver domain) hosting the disk.  Use the
          <code>name</code> attribute to specify the backend domain name.
          <span class="since">Since 1.2.13 (Xen only)</span>
      </dd>
3644 3645 3646
      <dt><code>boot</code></dt>
      <dd>Specifies that the disk is bootable. The <code>order</code>
        attribute determines the order in which devices will be tried during
3647 3648 3649 3650 3651 3652 3653
        boot sequence. On the S390 architecture only the first boot device is
        used. The optional <code>loadparm</code> attribute is an 8 character
        string which can be queried by guests on S390 via sclp or diag 308.
        Linux guests on S390 can use <code>loadparm</code> to select a boot
        entry. <span class="since">Since 3.5.0</span>
        The per-device <code>boot</code> elements cannot be used together
        with general boot elements in
3654 3655 3656
        <a href="#elementsOSBIOS">BIOS bootloader</a> section.
        <span class="since">Since 0.8.8</span>
      </dd>
3657
      <dt><code>encryption</code></dt>
3658 3659 3660 3661 3662
      <dd>Starting with <span class="since">libvirt 3.9.0</span> the
        <code>encryption</code> element is preferred to be a sub-element
        of the <code>source</code> element. If present, specifies how the
        volume is encrypted using "qcow". See the
        <a href="formatstorageencryption.html">Storage Encryption</a> page
3663 3664
        for more information.
      </dd>
3665 3666 3667
      <dt><code>readonly</code></dt>
      <dd>If present, this indicates the device cannot be modified by
        the guest.  For now, this is the default for disks with
3668
        attribute <code>device='cdrom'</code>.
3669
      </dd>
3670 3671 3672 3673 3674
      <dt><code>shareable</code></dt>
      <dd>If present, this indicates the device is expected to be shared
          between domains (assuming the hypervisor and OS support this),
          which means that caching should be deactivated for that device.
      </dd>
3675 3676 3677 3678 3679 3680 3681
      <dt><code>transient</code></dt>
      <dd>If present, this indicates that changes to the device
        contents should be reverted automatically when the guest
        exits.  With some hypervisors, marking a disk transient
        prevents the domain from participating in migration or
        snapshots. <span class="since">Since 0.9.5</span>
      </dd>
3682 3683
      <dt><code>serial</code></dt>
      <dd>If present, this specify serial number of virtual hard drive.
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          For example, it may look
          like <code>&lt;serial&gt;WD-WMAP9A966149&lt;/serial&gt;</code>.
3686 3687 3688
          Not supported for scsi-block devices, that is those using
          disk <code>type</code> 'block' using <code>device</code> 'lun'
          on <code>bus</code> 'scsi'.
3689 3690
          <span class="since">Since 0.7.1</span>
      </dd>
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      <dt><code>wwn</code></dt>
      <dd>If present, this element specifies the WWN (World Wide Name)
        of a virtual hard disk or CD-ROM drive. It must be composed
3694
        of 16 hexadecimal digits.
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        <span class='since'>Since 0.10.1</span>
      </dd>
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      <dt><code>vendor</code></dt>
      <dd>If present, this element specifies the vendor of a virtual hard
        disk or CD-ROM device. It must not be longer than 8 printable
        characters.
        <span class='since'>Since 1.0.1</span>
      </dd>
      <dt><code>product</code></dt>
      <dd>If present, this element specifies the product of a virtual hard
        disk or CD-ROM device. It must not be longer than 16 printable
        characters.
        <span class='since'>Since 1.0.1</span>
      </dd>
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      <dt><code>address</code></dt>
      <dd>If present, the <code>address</code> element ties the disk
        to a given slot of a controller (the
        actual <code>&lt;controller&gt;</code> device can often be
        inferred by libvirt, although it can
        be <a href="#elementsControllers">explicitly specified</a>).
        The <code>type</code> attribute is mandatory, and is typically
        "pci" or "drive".  For a "pci" controller, additional
        attributes for <code>bus</code>, <code>slot</code>,
3718 3719 3720 3721 3722
        and <code>function</code> must be present, as well as
        optional <code>domain</code> and <code>multifunction</code>.
        Multifunction defaults to 'off'; any other value requires
        QEMU 0.1.3 and <span class="since">libvirt 0.9.7</span>.  For a
        "drive" controller, additional attributes
3723 3724 3725
        <code>controller</code>, <code>bus</code>, <code>target</code>
        (<span class="since">libvirt 0.9.11</span>), and <code>unit</code>
        are available, each defaulting to 0.
3726 3727
      </dd>
      <dt><code>auth</code></dt>
3728 3729 3730 3731 3732 3733 3734 3735
      <dd>Starting with <span class="since">libvirt 3.9.0</span> the
        <code>auth</code> element is preferred to be a sub-element of
        the <code>source</code> element. The element is still read and
        managed as a <code>disk</code> sub-element. It is invalid to use
        <code>auth</code> as both a sub-element of <code>disk</code>
        and <code>source</code>. The <code>auth</code> element was
        introduced as a <code>disk</code> sub-element in
        <span class="since">libvirt 0.9.7.</span>
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      </dd>
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      <dt><code>geometry</code></dt>
      <dd>The optional <code>geometry</code> element provides the
        ability to override geometry settings. This mostly useful for
        S390 DASD-disks or older DOS-disks.  <span class="since">0.10.0</span>
        <dl>
          <dt><code>cyls</code></dt>
          <dd>The <code>cyls</code> attribute is the
            number of cylinders. </dd>
          <dt><code>heads</code></dt>
          <dd>The <code>heads</code> attribute is the
            number of heads. </dd>
          <dt><code>secs</code></dt>
          <dd>The <code>secs</code> attribute is the
            number of sectors per track. </dd>
          <dt><code>trans</code></dt>
          <dd>The optional <code>trans</code> attribute is the
            BIOS-Translation-Modus (none, lba or auto)</dd>
        </dl>
      </dd>
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      <dt><code>blockio</code></dt>
      <dd>If present, the <code>blockio</code> element allows
3758 3759 3760 3761 3762 3763 3764 3765
        to override any of the block device properties listed below.
        <span class="since">Since 0.10.2 (QEMU and KVM)</span>
        <dl>
          <dt><code>logical_block_size</code></dt>
          <dd>The logical block size the disk will report to the guest
            OS. For Linux this would be the value returned by the
            BLKSSZGET ioctl and describes the smallest units for disk
            I/O.
3766
          </dd>
3767 3768 3769 3770 3771
          <dt><code>physical_block_size</code></dt>
          <dd>The physical block size the disk will report to the guest
            OS. For Linux this would be the value returned by the
            BLKPBSZGET ioctl and describes the disk's hardware sector
            size which can be relevant for the alignment of disk data.
3772
          </dd>
3773 3774
        </dl>
      </dd>
D
Daniel P. Berrange 已提交
3775 3776
    </dl>

3777
    <h4><a id="elementsFilesystems">Filesystems</a></h4>
3778 3779 3780 3781 3782 3783 3784

    <p>
      A directory on the host that can be accessed directly from the guest.
      <span class="since">since 0.3.3, since 0.8.5 for QEMU/KVM</span>
    </p>

<pre>
3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803
...
&lt;devices&gt;
  &lt;filesystem type='template'&gt;
    &lt;source name='my-vm-template'/&gt;
    &lt;target dir='/'/&gt;
  &lt;/filesystem&gt;
  &lt;filesystem type='mount' accessmode='passthrough'&gt;
    &lt;driver type='path' wrpolicy='immediate'/&gt;
    &lt;source dir='/export/to/guest'/&gt;
    &lt;target dir='/import/from/host'/&gt;
    &lt;readonly/&gt;
  &lt;/filesystem&gt;
  &lt;filesystem type='file' accessmode='passthrough'&gt;
    &lt;driver name='loop' type='raw'/&gt;
    &lt;driver type='path' wrpolicy='immediate'/&gt;
    &lt;source file='/export/to/guest.img'/&gt;
    &lt;target dir='/import/from/host'/&gt;
    &lt;readonly/&gt;
  &lt;/filesystem&gt;
3804
  ...
3805 3806
&lt;/devices&gt;
...</pre>
3807 3808 3809 3810 3811 3812 3813 3814 3815

    <dl>
      <dt><code>filesystem</code></dt>
      <dd>

      The filesystem attribute <code>type</code> specifies the type of the
      <code>source</code>. The possible values are:

        <dl>
3816
        <dt><code>mount</code></dt>
3817 3818 3819 3820
        <dd>
        A host directory to mount in the guest. Used by LXC,
        OpenVZ <span class="since">(since 0.6.2)</span>
        and QEMU/KVM <span class="since">(since 0.8.5)</span>.
3821
        This is the default <code>type</code> if one is not specified.
3822 3823 3824 3825
        This mode also has an optional
        sub-element <code>driver</code>, with an
        attribute <code>type='path'</code>
        or <code>type='handle'</code> <span class="since">(since
3826 3827 3828 3829 3830 3831
        0.9.7)</span>. The driver block has an optional attribute
        <code>wrpolicy</code> that further controls interaction with
        the host page cache; omitting the attribute gives default behavior,
        while the value <code>immediate</code> means that a host writeback
        is immediately triggered for all pages touched during a guest file
        write operation <span class="since">(since 0.9.10)</span>.
3832
        </dd>
3833
        <dt><code>template</code></dt>
3834 3835 3836
        <dd>
        OpenVZ filesystem template. Only used by OpenVZ driver.
        </dd>
3837
        <dt><code>file</code></dt>
3838
        <dd>
3839 3840 3841
        A host file will be treated as an image and mounted in
        the guest. The filesystem format will be autodetected.
        Only used by LXC driver.
3842
        </dd>
3843
        <dt><code>block</code></dt>
3844
        <dd>
3845 3846 3847
        A host block device to mount in the guest. The filesystem
        format will be autodetected. Only used by LXC driver
        <span class="since">(since 0.9.5)</span>.
3848
        </dd>
3849
        <dt><code>ram</code></dt>
3850 3851 3852
        <dd>
          An in-memory filesystem, using memory from the host OS.
          The source element has a single attribute <code>usage</code>
3853 3854
          which gives the memory usage limit in KiB, unless units
          are specified by the <code>units</code> attribute. Only used
3855 3856
          by LXC driver.
          <span class="since"> (since 0.9.13)</span></dd>
3857
        <dt><code>bind</code></dt>
3858 3859 3860 3861
        <dd>
          A directory inside the guest will be bound to another
          directory inside the guest. Only used by LXC driver
          <span class="since"> (since 0.9.13)</span></dd>
3862 3863
        </dl>

3864
      The filesystem block has an optional attribute <code>accessmode</code>
3865 3866 3867 3868 3869 3870
      which specifies the security mode for accessing the source
      <span class="since">(since 0.8.5)</span>. Currently this only works
      with <code>type='mount'</code> for the QEMU/KVM driver. The possible
      values are:

        <dl>
3871
        <dt><code>passthrough</code></dt>
3872 3873
        <dd>
        The <code>source</code> is accessed with the permissions of the
3874
        user inside the guest. This is the default <code>accessmode</code> if
3875 3876 3877
        one is not specified.
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
        </dd>
3878
        <dt><code>mapped</code></dt>
3879 3880 3881 3882 3883
        <dd>
        The <code>source</code> is accessed with the permissions of the
        hypervisor (QEMU process).
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
        </dd>
3884
        <dt><code>squash</code></dt>
3885 3886 3887 3888 3889 3890 3891 3892 3893
        <dd>
        Similar to 'passthrough', the exception is that failure of
        privileged operations like 'chown' are ignored. This makes a
        passthrough-like mode usable for people who run the hypervisor
        as non-root.
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-09/msg00121.html">More info</a>
        </dd>
        </dl>

3894 3895 3896 3897 3898
      <span class="since">Since 5.2.0</span>, the filesystem element
      has an optional attribute <code>model</code> with supported values
      "virtio-transitional", "virtio-non-transitional", or "virtio".
      See <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
      for more details.
3899 3900
      </dd>

3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911
      <dt><code>driver</code></dt>
      <dd>
        The optional driver element allows specifying further details
        related to the hypervisor driver used to provide the filesystem.
        <span class="since">Since 1.0.6</span>
        <ul>
          <li>
            If the hypervisor supports multiple backend drivers, then
            the <code>type</code> attribute selects the primary
            backend driver name, while the <code>format</code>
            attribute provides the format type. For example, LXC
3912 3913
            supports a type of "loop", with a format of "raw" or
            "nbd" with any format. QEMU supports a type of "path"
3914
            or "handle", but no formats. Virtuozzo driver supports
D
Dmitry Guryanov 已提交
3915
            a type of "ploop" with a format of "ploop".
3916
          </li>
3917 3918 3919 3920 3921
          <li>
          For virtio-backed devices,
          <a href="#elementsVirtio">Virtio-specific options</a> can also be
          set. (<span class="since">Since 3.5.0</span>)
          </li>
3922 3923 3924
        </ul>
      </dd>

3925 3926 3927 3928 3929
      <dt><code>source</code></dt>
      <dd>
        The resource on the host that is being accessed in the guest. The
        <code>name</code> attribute must be used with
        <code>type='template'</code>, and the <code>dir</code> attribute must
3930
        be used with <code>type='mount'</code>. The <code>usage</code> attribute
3931 3932
        is used with <code>type='ram'</code> to set the memory limit in KiB,
        unless units are specified by the <code>units</code> attribute.
3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944
      </dd>

      <dt><code>target</code></dt>
      <dd>
        Where the <code>source</code> can be accessed in the guest. For
        most drivers this is an automatic mount point, but for QEMU/KVM
        this is merely an arbitrary string tag that is exported to the
        guest as a hint for where to mount.
      </dd>

      <dt><code>readonly</code></dt>
      <dd>
3945
        Enables exporting filesystem as a readonly mount for guest, by
3946 3947
        default read-write access is given (currently only works for
        QEMU/KVM driver).
3948
      </dd>
3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962

      <dt><code>space_hard_limit</code></dt>
      <dd>
        Maximum space available to this guest's filesystem.
        <span class="since">Since 0.9.13</span>
      </dd>

      <dt><code>space_soft_limit</code></dt>
      <dd>
        Maximum space available to this guest's filesystem. The container is
        permitted to exceed its soft limits for a grace period of time. Afterwards the
        hard limit is enforced.
        <span class="since">Since 0.9.13</span>
      </dd>
3963 3964
    </dl>

3965
    <h4><a id="elementsAddress">Device Addresses</a></h4>
3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983

    <p>
      Many devices have an optional <code>&lt;address&gt;</code>
      sub-element to describe where the device is placed on the
      virtual bus presented to the guest.  If an address (or any
      optional attribute within an address) is omitted on
      input, libvirt will generate an appropriate address; but an
      explicit address is required if more control over layout is
      required.  See below for device examples including an address
      element.
    </p>

    <p>
      Every address has a mandatory attribute <code>type</code> that
      describes which bus the device is on.  The choice of which
      address to use for a given device is constrained in part by the
      device and the architecture of the guest.  For example,
      a <code>&lt;disk&gt;</code> device
3984
      uses <code>type='drive'</code>, while
3985 3986 3987 3988 3989 3990 3991 3992
      a <code>&lt;console&gt;</code> device would
      use <code>type='pci'</code> on i686 or x86_64 guests,
      or <code>type='spapr-vio'</code> on PowerPC64 pseries guests.
      Each address type has further optional attributes that control
      where on the bus the device will be placed:
    </p>

    <dl>
3993
      <dt><code>pci</code></dt>
3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005
      <dd>PCI addresses have the following additional
        attributes: <code>domain</code> (a 2-byte hex integer, not
        currently used by qemu), <code>bus</code> (a hex value between
        0 and 0xff, inclusive), <code>slot</code> (a hex value between
        0x0 and 0x1f, inclusive), and <code>function</code> (a value
        between 0 and 7, inclusive).  Also available is
        the <code>multifunction</code> attribute, which controls
        turning on the multifunction bit for a particular
        slot/function in the PCI control register
        (<span class="since">since 0.9.7, requires QEMU
        0.13</span>). <code>multifunction</code> defaults to 'off',
        but should be set to 'on' for function 0 of a slot that will
4006 4007 4008 4009 4010 4011 4012 4013 4014
        have multiple functions used.
        (<span class="since">Since 4.10.0</span>), PCI address extensions
        depending on the architecture are supported. For example, PCI
        addresses for S390 guests will have a <code>zpci</code> child
        element, with two attributes: <code>uid</code> (a hex value
        between 0x0001 and 0xffff, inclusive), and <code>fid</code> (a
        hex value between 0x00000000 and 0xffffffff, inclusive) used by
        PCI devices on S390 for User-defined Identifiers and Function
        Identifiers.<br/>
4015 4016 4017 4018 4019 4020
        <span class="since">Since 1.3.5</span>, some hypervisor
        drivers may accept an <code>&lt;address type='pci'/&gt;</code>
        element with no other attributes as an explicit request to
        assign a PCI address for the device rather than some other
        type of address that may also be appropriate for that same
        device (e.g. virtio-mmio).
4021
      </dd>
4022
      <dt><code>drive</code></dt>
4023 4024 4025
      <dd>Drive addresses have the following additional
        attributes: <code>controller</code> (a 2-digit controller
        number), <code>bus</code> (a 2-digit bus number),
4026
        <code>target</code> (a 2-digit target number),
4027 4028
        and <code>unit</code> (a 2-digit unit number on the bus).
      </dd>
4029
      <dt><code>virtio-serial</code></dt>
4030 4031 4032 4033 4034
      <dd>Each virtio-serial address has the following additional
        attributes: <code>controller</code> (a 2-digit controller
        number), <code>bus</code> (a 2-digit bus number),
        and <code>slot</code> (a 2-digit slot within the bus).
      </dd>
4035
      <dt><code>ccid</code></dt>
4036 4037 4038 4039
      <dd>A CCID address, for smart-cards, has the following
        additional attributes: <code>bus</code> (a 2-digit bus
        number), and <code>slot</code> attribute (a 2-digit slot
        within the bus).  <span class="since">Since 0.8.8.</span>
4040
      </dd>
4041
      <dt><code>usb</code></dt>
4042 4043 4044 4045 4046
      <dd>USB addresses have the following additional
        attributes: <code>bus</code> (a hex value between 0 and 0xfff,
        inclusive), and <code>port</code> (a dotted notation of up to
        four octets, such as 1.2 or 2.1.3.1).
      </dd>
4047
      <dt><code>spapr-vio</code></dt>
4048 4049 4050 4051 4052 4053 4054 4055
      <dd>On PowerPC pseries guests, devices can be assigned to the
        SPAPR-VIO bus.  It has a flat 64-bit address space; by
        convention, devices are generally assigned at a non-zero
        multiple of 0x1000, but other addresses are valid and
        permitted by libvirt.  Each address has the following
        additional attribute: <code>reg</code> (the hex value address
        of the starting register).  <span class="since">Since
        0.9.9.</span>
4056
      </dd>
4057
      <dt><code>ccw</code></dt>
B
Boris Fiuczynski 已提交
4058
      <dd>S390 guests with a <code>machine</code> value of
4059 4060 4061 4062 4063 4064 4065
        s390-ccw-virtio use the native CCW bus for I/O devices.
        CCW bus addresses have the following additional attributes:
        <code>cssid</code> (a hex value between 0 and 0xfe, inclusive),
        <code>ssid</code> (a value between 0 and 3, inclusive) and
        <code>devno</code> (a hex value between 0 and 0xffff, inclusive).
        Partially specified bus addresses are not allowed.
        If omitted, libvirt will assign a free bus address with
4066 4067
        cssid=0xfe and ssid=0. Virtio-ccw devices must have their cssid
        set to 0xfe.
4068
        <span class="since">Since 1.0.4</span>
4069
      </dd>
4070 4071 4072 4073 4074
      <dt><code>virtio-mmio</code></dt>
      <dd>This places the device on the virtio-mmio transport, which is
        currently only available for some <code>armv7l</code> and
        <code>aarch64</code> virtual machines. virtio-mmio addresses
        do not have any additional attributes.
4075 4076 4077 4078 4079 4080 4081
        <span class="since">Since 1.1.3</span><br/>
        If the guest architecture is <code>aarch64</code> and the machine
        type is <code>virt</code>, libvirt will automatically assign PCI
        addresses to devices; however, the presence of a single device
        with virtio-mmio address in the guest configuration will cause
        libvirt to assign virtio-mmio addresses to all further devices.
        <span class="since">Since 3.0.0</span>
4082
      </dd>
4083
      <dt><code>isa</code></dt>
H
Hu Tao 已提交
4084 4085 4086 4087
      <dd>ISA addresses have the following additional
        attributes: <code>iobase</code> and <code>irq</code>.
        <span class="since">Since 1.2.1</span>
      </dd>
4088 4089
    </dl>

4090
    <h4><a id="elementsVirtio">Virtio-related options</a></h4>
4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102

    <p>
      QEMU's virtio devices have some attributes related to the virtio transport under
      the <code>driver</code> element:
      The <code>iommu</code> attribute enables the use of emulated IOMMU
      by the device. The attribute <code>ats</code> controls the Address
      Translation Service support for PCIe devices. This is needed to make use
      of IOTLB support (see <a href="#elementsIommu">IOMMU device</a>).
      Possible values are <code>on</code> or <code>off</code>.
      <span class="since">Since 3.5.0</span>
    </p>

4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141
    <h4><a id="elementsVirtioTransitional">Virtio transitional devices</a></h4>

    <p>
      <span class="since">Since 5.2.0</span>, some of QEMU's virtio devices,
      when used with PCI/PCIe machine types, accept the following
      <code>model</code> values:
    </p>

    <dl>
      <dt><code>virtio-transitional</code></dt>
      <dd>This device can work both with virtio 0.9 and virtio 1.0 guest
      drivers, so it's the best choice when compatibility with older
      guest operating systems is desired. libvirt will plug the device
      into a conventional PCI slot.
      </dd>
      <dt><code>virtio-non-transitional</code></dt>
      <dd>This device can only work with virtio 1.0 guest drivers, and it's
      the recommended option unless compatibility with older guest
      operating systems is necessary. libvirt will plug the device into
      either a PCI Express slot or a conventional PCI slot based on the
      machine type, resulting in a more optimized PCI topology.
      </dd>
      <dt><code>virtio</code></dt>
      <dd>This device will work like a <code>virtio-non-transitional</code>
      device when plugged into a PCI Express slot, and like a
      <code>virtio-transitional</code> device otherwise; libvirt will
      pick one or the other based on the machine type. This is the best
      choice when compatibility with libvirt versions older than 5.1.0
      is necessary, but it's otherwise not recommended to use it.
      </dd>
    </dl>

    <p>
      For more details see the
      <a href="https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg00923.html">qemu patch posting</a> and the
      <a href="http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.html">virtio-1.0 spec</a>.
    </p>


4142
    <h4><a id="elementsControllers">Controllers</a></h4>
E
Eric Blake 已提交
4143 4144

    <p>
4145
      Depending on the guest architecture, some device buses can
4146 4147
      appear more than once, with a group of virtual devices tied to a
      virtual controller.  Normally, libvirt can automatically infer such
E
Eric Blake 已提交
4148
      controllers without requiring explicit XML markup, but sometimes
4149 4150 4151
      it is necessary to provide an explicit controller element, notably
      when planning the <a href="pci-hotplug.html">PCI topology</a>
      for guests where device hotplug is expected.
E
Eric Blake 已提交
4152 4153 4154
    </p>

<pre>
4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165
...
&lt;devices&gt;
  &lt;controller type='ide' index='0'/&gt;
  &lt;controller type='virtio-serial' index='0' ports='16' vectors='4'/&gt;
  &lt;controller type='virtio-serial' index='1'&gt;
    &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/&gt;
  &lt;/controller&gt;
  &lt;controller type='scsi' index='0' model='virtio-scsi'&gt;
    &lt;driver iothread='4'/&gt;
    &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x0b' function='0x0'/&gt;
  &lt;/controller&gt;
E
Eric Blake 已提交
4166
  ...
4167 4168
&lt;/devices&gt;
...</pre>
E
Eric Blake 已提交
4169 4170 4171

    <p>
      Each controller has a mandatory attribute <code>type</code>,
4172 4173
      which must be one of 'ide', 'fdc', 'scsi', 'sata', 'usb',
      'ccid', 'virtio-serial' or 'pci', and a mandatory
4174 4175
      attribute <code>index</code> which is the decimal integer
      describing in which order the bus controller is encountered (for
4176
      use in <code>controller</code> attributes of
4177 4178 4179 4180 4181
      <code>&lt;address&gt;</code> elements).
      <span class="since">Since 1.3.5</span> the index is optional; if
      not specified, it will be auto-assigned to be the lowest unused
      index for the given controller type. Some controller types have
      additional attributes that control specific features, such as:
4182 4183 4184 4185 4186 4187 4188
    </p>

      <dl>
        <dt><code>virtio-serial</code></dt>
        <dd>The <code>virtio-serial</code> controller has two additional
        optional attributes <code>ports</code> and <code>vectors</code>,
        which control how many devices can be connected through the
4189 4190 4191 4192 4193 4194
        controller. <span class="since">Since 5.2.0</span>, it
        supports an optional attribute <code>model</code> which can
        be 'virtio', 'virtio-transitional', or 'virtio-non-transitional'. See
        <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
        for more details.
        </dd>
4195 4196 4197 4198 4199 4200 4201 4202 4203
        <dt><code>scsi</code></dt>
        <dd>A <code>scsi</code> controller has an optional attribute
        <code>model</code>, which is one of 'auto', 'buslogic', 'ibmvscsi',
        'lsilogic', 'lsisas1068', 'lsisas1078', 'virtio-scsi' or
        'vmpvscsi'.</dd>
        <dt><code>usb</code></dt>
        <dd>A <code>usb</code> controller has an optional attribute
        <code>model</code>, which is one of "piix3-uhci", "piix4-uhci",
        "ehci", "ich9-ehci1", "ich9-uhci1", "ich9-uhci2", "ich9-uhci3",
4204
        "vt82c686b-uhci", "pci-ohci", "nec-xhci", "qusb1" (xen pvusb
4205 4206
        with qemu backend, version 1.1), "qusb2" (xen pvusb with qemu
        backend, version 2.0) or "qemu-xhci". Additionally,
4207 4208 4209 4210 4211 4212 4213
         <span class="since">since 0.10.0</span>, if the USB bus needs to
         be explicitly disabled for the guest, <code>model='none'</code>
         may be used.  <span class="since">Since 1.0.5</span>, no default
         USB controller will be built on s390.
         <span class="since">Since 1.3.5</span>, USB controllers accept a
         <code>ports</code> attribute to configure how many devices can be
         connected to the controller.</dd>
4214 4215 4216 4217
        <dt><code>ide</code></dt>
        <dd><span class="since">Since 3.10.0</span> for the vbox driver, the
        <code>ide</code> controller has an optional attribute
        <code>model</code>, which is one of "piix3", "piix4" or "ich6".</dd>
4218 4219 4220 4221 4222
      </dl>

    <p>
      Note: The PowerPC64 "spapr-vio" addresses do not have an
      associated controller.
E
Eric Blake 已提交
4223 4224 4225 4226 4227 4228
    </p>

    <p>
      For controllers that are themselves devices on a PCI or USB bus,
      an optional sub-element <code>&lt;address&gt;</code> can specify
      the exact relationship of the controller to its master bus, with
4229
      semantics <a href="#elementsAddress">given above</a>.
E
Eric Blake 已提交
4230 4231
    </p>

4232 4233
    <p>
      An optional sub-element <code>driver</code> can specify the driver
4234
      specific options:
4235
    </p>
4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258
    <dl>
      <dt><code>queues</code></dt>
      <dd>
        The optional <code>queues</code> attribute specifies the number of
        queues for the controller. For best performance, it's recommended to
        specify a value matching the number of vCPUs.
        <span class="since">Since 1.0.5 (QEMU and KVM only)</span>
      </dd>
      <dt><code>cmd_per_lun</code></dt>
      <dd>
        The optional <code>cmd_per_lun</code> attribute specifies the maximum
        number of commands that can be queued on devices controlled by the
        host.
        <span class="since">Since 1.2.7 (QEMU and KVM only)</span>
      </dd>
      <dt><code>max_sectors</code></dt>
      <dd>
        The optional <code>max_sectors</code> attribute specifies the maximum
        amount of data in bytes that will be transferred to or from the device
        in a single command. The transfer length is measured in sectors, where
        a sector is 512 bytes.
        <span class="since">Since 1.2.7 (QEMU and KVM only)</span>
      </dd>
4259 4260 4261 4262 4263 4264 4265 4266
      <dt><code>ioeventfd</code></dt>
      <dd>
        The optional <code>ioeventfd</code> attribute specifies
        whether the controller should use
        <a href='https://patchwork.kernel.org/patch/43390/'>
        I/O asynchronous handling</a> or not.  Accepted values are
        "on" and "off". <span class="since">Since 1.2.18</span>
      </dd>
4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283
      <dt><code>iothread</code></dt>
      <dd>
        Supported for controller type <code>scsi</code> using model
        <code>virtio-scsi</code> for <code>address</code> types
        <code>pci</code> and <code>ccw</code>
        <span class="since">since 1.3.5 (QEMU 2.4)</span>.

        The optional <code>iothread</code> attribute assigns the controller
        to an IOThread as defined by the range for the domain
        <a href="#elementsIOThreadsAllocation"><code>iothreads</code></a>
        value. Each SCSI <code>disk</code> assigned to use the specified
        <code>controller</code> will utilize the same IOThread. If a specific
        IOThread is desired for a specific SCSI <code>disk</code>, then
        multiple controllers must be defined each having a specific
        <code>iothread</code> value. The <code>iothread</code> value
        must be within the range 1 to the domain iothreads value.
      </dd>
4284 4285 4286 4287 4288 4289
      <dt>virtio options</dt>
      <dd>
        For virtio controllers,
        <a href="#elementsVirtio">Virtio-specific options</a> can also be
        set. (<span class="since">Since 3.5.0</span>)
      </dd>
4290
    </dl>
4291 4292 4293 4294 4295 4296
    <p>
      USB companion controllers have an optional
      sub-element <code>&lt;master&gt;</code> to specify the exact
      relationship of the companion to its master controller.
      A companion controller is on the same bus as its master, so
      the companion <code>index</code> value should be equal.
4297 4298 4299 4300 4301
      Not all controller models can be used as companion controllers
      and libvirt might provide some sensible defaults (settings
      of <code>master startport</code> and <code>function</code> of an
      address) for some particular models.
      Preferred companion controllers are <code>ich-uhci[123]</code>.
4302 4303 4304
    </p>

<pre>
4305 4306 4307 4308 4309 4310 4311 4312 4313
...
&lt;devices&gt;
  &lt;controller type='usb' index='0' model='ich9-ehci1'&gt;
    &lt;address type='pci' domain='0' bus='0' slot='4' function='7'/&gt;
  &lt;/controller&gt;
  &lt;controller type='usb' index='0' model='ich9-uhci1'&gt;
    &lt;master startport='0'/&gt;
    &lt;address type='pci' domain='0' bus='0' slot='4' function='0' multifunction='on'/&gt;
  &lt;/controller&gt;
4314
  ...
4315 4316
&lt;/devices&gt;
...</pre>
J
Ján Tomko 已提交
4317 4318

    <p>
4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339
      PCI controllers have an optional <code>model</code> attribute; possible
      values for this attribute are
    </p>
    <ul>
      <li>
        <code>pci-root</code>, <code>pci-bridge</code>
        (<span class="since">since 1.0.5</span>)
      </li>
      <li>
        <code>pcie-root</code>, <code>dmi-to-pci-bridge</code>
        (<span class="since">since 1.1.2</span>)
      </li>
      <li>
        <code>pcie-root-port</code>, <code>pcie-switch-upstream-port</code>,
        <code>pcie-switch-downstream-port</code>
        (<span class="since">since 1.2.19</span>)
      </li>
      <li>
        <code>pci-expander-bus</code>, <code>pcie-expander-bus</code>
        (<span class="since">since 1.3.4</span>)
      </li>
4340 4341 4342 4343
      <li>
        <code>pcie-to-pci-bridge</code>
        (<span class="since">since 4.3.0</span>)
      </li>
4344 4345 4346
    </ul>
    <p>
      The root controllers (<code>pci-root</code>
4347 4348 4349
      and <code>pcie-root</code>) have an
      optional <code>pcihole64</code> element specifying how big (in
      kilobytes, or in the unit specified by <code>pcihole64</code>'s
4350 4351 4352 4353 4354
      <code>unit</code> attribute) the 64-bit PCI hole should be. Some guests (like
      Windows XP or Windows Server 2003) might crash when QEMU and Seabios
      are recent enough to support 64-bit PCI holes, unless this is disabled
      (set to 0). <span class="since">Since 1.1.2 (QEMU only)</span>
    </p>
4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367
    <p>
      PCI controllers also have an optional
      subelement <code>&lt;model&gt;</code> with an attribute
      <code>name</code>. The name attribute holds the name of the
      specific device that qemu is emulating (e.g. "i82801b11-bridge")
      rather than simply the class of device ("dmi-to-pci-bridge",
      "pci-bridge"), which is set in the controller element's
      model <b>attribute</b>.  In almost all cases, you should not
      manually add a <code>&lt;model&gt;</code> subelement to a
      controller, nor should you modify one that is automatically
      generated by libvirt. <span class="since">Since 1.2.19 (QEMU
      only).</span>
    </p>
4368 4369
    <p>
      PCI controllers also have an optional
4370 4371 4372
      subelement <code>&lt;target&gt;</code> with the attributes and
      subelements listed below. These are configurable items that 1)
      are visible to the guest OS so must be preserved for guest ABI
4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388
      compatibility, and 2) are usually left to default values or
      derived automatically by libvirt. In almost all cases, you
      should not manually add a <code>&lt;target&gt;</code> subelement
      to a controller, nor should you modify the values in the those
      that are automatically generated by
      libvirt. <span class="since">Since 1.2.19 (QEMU only).</span>
    </p>
    <dl>
      <dt><code>chassisNr</code></dt>
      <dd>
        PCI controllers that have attribute model="pci-bridge", can
        also have a <code>chassisNr</code> attribute in
        the <code>&lt;target&gt;</code> subelement, which is used to
        control QEMU's "chassis_nr" option for the pci-bridge device
        (normally libvirt automatically sets this to the same value as
        the index attribute of the pci controller). If set, chassisNr
4389
        must be between 1 and 255.
4390
      </dd>
4391 4392
      <dt><code>chassis</code></dt>
      <dd>
4393 4394
        pcie-root-port and pcie-switch-downstream-port controllers can
        also have a <code>chassis</code> attribute in
4395 4396 4397 4398 4399 4400 4401
        the <code>&lt;target&gt;</code> subelement, which is used to
        set the controller's "chassis" configuration value, which is
        visible to the virtual machine. If set, chassis must be
        between 0 and 255.
      </dd>
      <dt><code>port</code></dt>
      <dd>
4402 4403 4404
        pcie-root-port and pcie-switch-downstream-port controllers can
        also have a <code>port</code> attribute in
        the <code>&lt;target&gt;</code> subelement, which
4405 4406 4407 4408
        is used to set the controller's "port" configuration value,
        which is visible to the virtual machine. If set, port must be
        between 0 and 255.
      </dd>
4409 4410
      <dt><code>busNr</code></dt>
      <dd>
4411
        pci-expander-bus and pcie-expander-bus controllers can have an
4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425
        optional <code>busNr</code> attribute (1-254). This will be
        the bus number of the new bus; All bus numbers between that
        specified and 255 will be available only for assignment to
        PCI/PCIe controllers plugged into the hierarchy starting with
        this expander bus, and bus numbers less than the specified
        value will be available to the next lower expander-bus (or the
        root-bus if there are no lower expander buses). If you do not
        specify a busNumber, libvirt will find the lowest existing
        busNumber in all other expander buses (or use 256 if there are
        no others) and auto-assign the busNr of that found bus - 2,
        which provides one bus number for the pci-expander-bus and one
        for the pci-bridge that is automatically attached to it (if
        you plan on adding more pci-bridges to the hierarchy of the
        bus, you should manually set busNr to a lower value).
4426 4427 4428 4429 4430 4431 4432
        <p>
          A similar algorithm is used for automatically determining
          the busNr attribute for pcie-expander-bus, but since the
          pcie-expander-bus doesn't have any built-in pci-bridge, the
          2nd bus-number is just being reserved for the pcie-root-port
          that must necessarily be connected to the bus in order to
          actually plug in an endpoint device. If you intend to plug
4433 4434 4435 4436 4437 4438 4439
          multiple devices into a pcie-expander-bus, you must connect
          a pcie-switch-upstream-port to the pcie-root-port that is
          plugged into the pcie-expander-bus, and multiple
          pcie-switch-downstream-ports to the
          pcie-switch-upstream-port, and of course for this to work
          properly, you will need to decrease the pcie-expander-bus'
          busNr accordingly so that there are enough unused bus
V
Ville Skyttä 已提交
4440
          numbers above it to accommodate giving out one bus number for
4441 4442 4443
          the upstream-port and one for each downstream-port (in
          addition to the pcie-root-port and the pcie-expander-bus
          itself).
4444
        </p>
4445
      </dd>
4446
      <dt><code>node</code></dt>
4447
      <dd>
4448 4449 4450 4451
        Some PCI controllers (<code>pci-expander-bus</code> for the pc
        machine type, <code>pcie-expander-bus</code> for the q35 machine
        type and, <span class="since">since 3.6.0</span>,
        <code>pci-root</code> for the pseries machine type) can have an
4452 4453 4454 4455 4456 4457 4458 4459
        optional <code>&lt;node&gt;</code> subelement within
        the <code>&lt;target&gt;</code> subelement, which is used to
        set the NUMA node reported to the guest OS for that bus - the
        guest OS will then know that all devices on that bus are a
        part of the specified NUMA node (it is up to the user of the
        libvirt API to attach host devices to the correct
        pci-expander-bus when assigning them to the domain).
      </dd>
4460 4461 4462 4463 4464 4465
      <dt><code>index</code></dt>
      <dd>
        pci-root controllers for pSeries guests use this attribute to
        record the order they will show up in the guest.
        <span class="since">Since 3.6.0</span>
      </dd>
4466
    </dl>
4467
    <p>
L
Laine Stump 已提交
4468
      For machine types which provide an implicit PCI bus, the pci-root
J
Ján Tomko 已提交
4469
      controller with index=0 is auto-added and required to use PCI devices.
L
Laine Stump 已提交
4470
      pci-root has no address.
4471 4472 4473
      PCI bridges are auto-added if there are too many devices to fit on
      the one bus provided by pci-root, or a PCI bus number greater than zero
      was specified.
J
Ján Tomko 已提交
4474 4475 4476 4477 4478 4479
      PCI bridges can also be specified manually, but their addresses should
      only refer to PCI buses provided by already specified PCI controllers.
      Leaving gaps in the PCI controller indexes might lead to an invalid
      configuration.
    </p>
<pre>
4480 4481 4482 4483 4484 4485 4486 4487
...
&lt;devices&gt;
  &lt;controller type='pci' index='0' model='pci-root'/&gt;
  &lt;controller type='pci' index='1' model='pci-bridge'&gt;
    &lt;address type='pci' domain='0' bus='0' slot='5' function='0' multifunction='off'/&gt;
  &lt;/controller&gt;
&lt;/devices&gt;
...</pre>
L
Laine Stump 已提交
4488 4489 4490 4491 4492 4493

    <p>
      For machine types which provide an implicit PCI Express (PCIe)
      bus (for example, the machine types based on the Q35 chipset),
      the pcie-root controller with index=0 is auto-added to the
      domain's configuration. pcie-root has also no address, provides
4494 4495 4496 4497
      31 slots (numbered 1-31) that can be used to attach PCIe or PCI
      devices (although libvirt will never auto-assign a PCI device to
      a PCIe slot, it will allow manual specification of such an
      assignment). Devices connected to pcie-root cannot be
4498 4499 4500 4501 4502 4503 4504 4505
      hotplugged. If traditional PCI devices are present in the guest
      configuration, a <code>pcie-to-pci-bridge</code> controller will
      automatically be added: this controller, which plugs into a
      <code>pcie-root-port</code>, provides 31 usable PCI slots (1-31) with
      hotplug support (<span class="since">since 4.3.0</span>). If the QEMU
      binary doesn't support the corresponding device, then a
      <code>dmi-to-pci-bridge</code> controller will be added instead,
      usually at the defacto standard location of slot=0x1e. A
4506 4507 4508
      dmi-to-pci-bridge controller plugs into a PCIe slot (as provided
      by pcie-root), and itself provides 31 standard PCI slots (which
      also do not support device hotplug). In order to have
4509 4510 4511
      hot-pluggable PCI slots in the guest system, a pci-bridge
      controller will also be automatically created and connected to
      one of the slots of the auto-created dmi-to-pci-bridge
4512
      controller; all guest PCI devices with addresses that are
4513 4514
      auto-determined by libvirt will be placed on this pci-bridge
      device.  (<span class="since">since 1.1.2</span>).
L
Laine Stump 已提交
4515
    </p>
4516 4517
    <p>
      Domains with an implicit pcie-root can also add controllers
4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543
      with <code>model='pcie-root-port'</code>,
      <code>model='pcie-switch-upstream-port'</code>,
      and <code>model='pcie-switch-downstream-port'</code>. pcie-root-port
      is a simple type of bridge device that can connect only to one
      of the 31 slots on the pcie-root bus on its upstream side, and
      makes a single (PCIe, hotpluggable) port available on the
      downstream side (at slot='0'). pcie-root-port can be used to
      provide a single slot to later hotplug a PCIe device (but is not
      itself hotpluggable - it must be in the configuration when the
      domain is started).
      (<span class="since">since 1.2.19</span>)
    </p>
    <p>
      pcie-switch-upstream-port is a more flexible (but also more
      complex) device that can only plug into a pcie-root-port or
      pcie-switch-downstream-port on the upstream side (and only
      before the domain is started - it is not hot-pluggable), and
      provides 32 ports on the downstream side (slot='0' - slot='31')
      that accept only pcie-switch-downstream-port devices; each
      pcie-switch-downstream-port device can only plug into a
      pcie-switch-upstream-port on its upstream side (again, not
      hot-pluggable), and on its downstream side provides a single
      hotpluggable pcie port that can accept any standard pci or pcie
      device (or another pcie-switch-upstream-port), i.e. identical in
      function to a pcie-root-port.  (<span class="since">since
      1.2.19</span>)
4544
    </p>
L
Laine Stump 已提交
4545
<pre>
4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556
...
&lt;devices&gt;
  &lt;controller type='pci' index='0' model='pcie-root'/&gt;
  &lt;controller type='pci' index='1' model='dmi-to-pci-bridge'&gt;
    &lt;address type='pci' domain='0' bus='0' slot='0xe' function='0'/&gt;
  &lt;/controller&gt;
  &lt;controller type='pci' index='2' model='pci-bridge'&gt;
    &lt;address type='pci' domain='0' bus='1' slot='1' function='0'/&gt;
  &lt;/controller&gt;
&lt;/devices&gt;
...</pre>
4557

4558
    <h4><a id="elementsLease">Device leases</a></h4>
4559 4560 4561 4562 4563 4564 4565 4566

    <p>
      When using a lock manager, it may be desirable to record device leases
      against a VM. The lock manager will ensure the VM won't start unless
      the leases can be acquired.
    </p>

<pre>
4567 4568
...
&lt;devices&gt;
4569
  ...
4570 4571 4572 4573 4574 4575 4576 4577
  &lt;lease&gt;
    &lt;lockspace&gt;somearea&lt;/lockspace&gt;
    &lt;key&gt;somekey&lt;/key&gt;
    &lt;target path='/some/lease/path' offset='1024'/&gt;
  &lt;/lease&gt;
  ...
&lt;/devices&gt;
...</pre>
4578 4579

    <dl>
4580
      <dt><code>lockspace</code></dt>
4581 4582 4583 4584
      <dd>This is an arbitrary string, identifying the lockspace
        within which the key is held. Lock managers may impose
        extra restrictions on the format, or length of the lockspace
        name.</dd>
4585
      <dt><code>key</code></dt>
4586 4587 4588 4589
      <dd>This is an arbitrary string, uniquely identifying the
        lease to be acquired. Lock managers may impose extra
        restrictions on the format, or length of the key.
      </dd>
4590
      <dt><code>target</code></dt>
4591 4592 4593
      <dd>This is the fully qualified path of the file associated
        with the lockspace. The offset specifies where the lease
        is stored within the file. If the lock manager does not
V
Ville Skyttä 已提交
4594
        require an offset, just pass 0.
4595 4596
      </dd>
    </dl>
E
Eric Blake 已提交
4597

4598
    <h4><a id="elementsHostDev">Host device assignment</a></h4>
4599

4600
    <h5><a id="elementsHostDevSubsys">USB / PCI / SCSI devices</a></h5>
4601 4602

    <p>
H
Han Cheng 已提交
4603
      USB, PCI and SCSI devices attached to the host can be passed through
4604
      to the guest using the <code>hostdev</code> element.
4605 4606
      <span class="since">since after 0.4.4 for USB, 0.6.0 for PCI (KVM only)
        and 1.0.6 for SCSI (KVM only)</span>:
4607 4608
    </p>

4609
<pre>
4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620
...
&lt;devices&gt;
  &lt;hostdev mode='subsystem' type='usb'&gt;
    &lt;source startupPolicy='optional'&gt;
      &lt;vendor id='0x1234'/&gt;
      &lt;product id='0xbeef'/&gt;
    &lt;/source&gt;
    &lt;boot order='2'/&gt;
  &lt;/hostdev&gt;
&lt;/devices&gt;
...</pre>
4621

4622
    <p>or:</p>
4623 4624

<pre>
4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635
...
&lt;devices&gt;
  &lt;hostdev mode='subsystem' type='pci' managed='yes'&gt;
    &lt;source&gt;
      &lt;address domain='0x0000' bus='0x06' slot='0x02' function='0x0'/&gt;
    &lt;/source&gt;
    &lt;boot order='1'/&gt;
    &lt;rom bar='on' file='/etc/fake/boot.bin'/&gt;
  &lt;/hostdev&gt;
&lt;/devices&gt;
...</pre>
H
Han Cheng 已提交
4636 4637 4638 4639

    <p>or:</p>

<pre>
4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651
...
&lt;devices&gt;
  &lt;hostdev mode='subsystem' type='scsi' sgio='filtered' rawio='yes'&gt;
    &lt;source&gt;
      &lt;adapter name='scsi_host0'/&gt;
      &lt;address bus='0' target='0' unit='0'/&gt;
    &lt;/source&gt;
    &lt;readonly/&gt;
    &lt;address type='drive' controller='0' bus='0' target='0' unit='0'/&gt;
  &lt;/hostdev&gt;
&lt;/devices&gt;
...</pre>
4652

J
John Ferlan 已提交
4653 4654 4655 4656

    <p>or:</p>

<pre>
4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669
...
&lt;devices&gt;
  &lt;hostdev mode='subsystem' type='scsi'&gt;
    &lt;source protocol='iscsi' name='iqn.2014-08.com.example:iscsi-nopool/1'&gt;
      &lt;host name='example.com' port='3260'/&gt;
      &lt;auth username='myuser'&gt;
        &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
    &lt;/source&gt;
    &lt;address type='drive' controller='0' bus='0' target='0' unit='0'/&gt;
  &lt;/hostdev&gt;
&lt;/devices&gt;
...</pre>
J
John Ferlan 已提交
4670

4671 4672 4673 4674 4675 4676 4677 4678 4679
    <p>or:</p>

<pre>
  ...
  &lt;devices&gt;
    &lt;hostdev mode='subsystem' type='scsi_host'&gt;
      &lt;source protocol='vhost' wwpn='naa.50014057667280d8'/&gt;
    &lt;/hostdev&gt;
  &lt;/devices&gt;
4680 4681 4682 4683 4684 4685 4686 4687 4688
  ...</pre>

    <p>or:</p>

<pre>
  ...
  &lt;devices&gt;
    &lt;hostdev mode='subsystem' type='mdev' model='vfio-pci'&gt;
    &lt;source&gt;
4689
      &lt;address uuid='c2177883-f1bb-47f0-914d-32a22e3a8804'/&gt;
4690 4691
    &lt;/source&gt;
    &lt;/hostdev&gt;
4692 4693 4694 4695 4696 4697
    &lt;hostdev mode='subsystem' type='mdev' model='vfio-ccw'&gt;
    &lt;source&gt;
      &lt;address uuid='9063cba3-ecef-47b6-abcf-3fef4fdcad85'/&gt;
    &lt;/source&gt;
    &lt;address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0001'/&gt;
    &lt;/hostdev&gt;
4698
  &lt;/devices&gt;
4699 4700
  ...</pre>

4701 4702 4703
    <dl>
      <dt><code>hostdev</code></dt>
      <dd>The <code>hostdev</code> element is the main container for describing
J
John Ferlan 已提交
4704 4705 4706 4707
        host devices. For each device, the <code>mode</code> is always
        "subsystem" and the <code>type</code> is one of the following values
        with additional attributes noted.
        <dl>
4708
          <dt><code>usb</code></dt>
4709 4710 4711
          <dd>USB devices are detached from the host on guest startup
            and reattached after the guest exits or the device is
            hot-unplugged.
J
John Ferlan 已提交
4712
          </dd>
4713
          <dt><code>pci</code></dt>
J
John Ferlan 已提交
4714 4715 4716
          <dd>For PCI devices, when <code>managed</code> is "yes" it is
            detached from the host before being passed on to the guest
            and reattached to the host after the guest exits. If
4717 4718 4719 4720 4721 4722
            <code>managed</code> is omitted or "no", the user is
            responsible to call <code>virNodeDeviceDetachFlags</code>
            (or <code>virsh nodedev-detach</code> before starting the guest
            or hot-plugging the device and <code>virNodeDeviceReAttach</code>
            (or <code>virsh nodedev-reattach</code>) after hot-unplug or
            stopping the guest.
J
John Ferlan 已提交
4723
          </dd>
4724
          <dt><code>scsi</code></dt>
J
John Ferlan 已提交
4725
          <dd>For SCSI devices, user is responsible to make sure the device
4726 4727 4728 4729 4730 4731
            is not used by host. If supported by the hypervisor and OS, the
            optional <code>sgio</code> (<span class="since">since 1.0.6</span>)
            attribute indicates whether unprivileged SG_IO commands are
            filtered for the disk. Valid settings are "filtered" or
            "unfiltered", where the default is "filtered".
            The optional <code>rawio</code>
4732 4733 4734 4735 4736 4737
            (<span class="since">since 1.2.9</span>) attribute indicates
            whether the lun needs the rawio capability. Valid settings are
            "yes" or "no". See the rawio description within the
            <a href="#elementsDisks">disk</a> section.
            If a disk lun in the domain already has the rawio capability,
            then this setting not required.
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          </dd>
4739 4740 4741 4742
          <dt><code>scsi_host</code></dt>
          <dd><span class="since">since 2.5.0</span>For SCSI devices, user
            is responsible to make sure the device is not used by host. This
            <code>type</code> passes all LUNs presented by a single HBA to
4743 4744 4745 4746 4747 4748
            the guest. <span class="since">Since 5.2.0,</span> the
            <code>model</code> attribute can be specified further
            with "virtio-transitional", "virtio-non-transitional", or
            "virtio". See
            <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
            for more details.
4749
          </dd>
4750 4751 4752 4753
          <dt><code>mdev</code></dt>
          <dd>For mediated devices (<span class="since">Since 3.2.0</span>)
          the <code>model</code> attribute specifies the device API which
          determines how the host's vfio driver will expose the device to the
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          guest. Currently, <code>model='vfio-pci'</code>,
4755
          <code>model='vfio-ccw'</code> (<span class="since">Since 4.4.0</span>)
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          and <code>model='vfio-ap'</code> (<span class="since">Since 4.9.0</span>)
4757 4758 4759
          is supported. <a href="drvnodedev.html#MDEV">MDEV</a> section
          provides more information about mediated devices as well as how to
          create mediated devices on the host.
4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775
          <span class="since">Since 4.6.0 (QEMU 2.12)</span> an optional
          <code>display</code> attribute may be used to enable or disable
          support for an accelerated remote desktop backed by a mediated
          device (such as NVIDIA vGPU or Intel GVT-g) as an alternative to
          emulated <a href="#elementsVideo">video devices</a>. This attribute
          is limited to <code>model='vfio-pci'</code> only. Supported values
          are either <code>on</code> or <code>off</code> (default is 'off').
          It is required to use a
          <a href="#elementsGraphics">graphical framebuffer</a> in order to
          use this attribute, currently only supported with VNC, Spice and
          egl-headless graphics devices.
          <p>
            Note: There are also some implications on the usage of guest's
            address type depending on the <code>model</code> attribute,
            see the <code>address</code> element below.
          </p>
4776
          </dd>
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4777
        </dl>
4778
        <p>
4779 4780 4781 4782 4783 4784
          Note: The <code>managed</code> attribute is only used with
          <code>type='pci'</code> and is ignored by all the other device types,
          thus setting <code>managed</code> explicitly with other than a PCI
          device has the same effect as omitting it. Similarly,
          <code>model</code> attribute is only supported by mediated devices and
          ignored by all other device types.
4785
        </p>
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4786
      </dd>
4787
      <dt><code>source</code></dt>
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4788 4789 4790
      <dd>The source element describes the device as seen from the host using
        the following mechanism to describe:
        <dl>
4791
          <dt><code>usb</code></dt>
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4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818
          <dd>The USB device can either be addressed by vendor / product id
            using the <code>vendor</code> and <code>product</code> elements
            or by the device's address on the host using the
            <code>address</code> element.
            <p>
            <span class="since">Since 1.0.0</span>, the <code>source</code>
            element of USB devices may contain <code>startupPolicy</code>
            attribute which can be used to define policy what to do if the
            specified host USB device is not found. The attribute accepts
            the following values:
            </p>
            <table class="top_table">
              <tr>
                <td> mandatory </td>
                <td> fail if missing for any reason (the default) </td>
              </tr>
              <tr>
                <td> requisite </td>
                <td> fail if missing on boot up,
                     drop if missing on migrate/restore/revert </td>
              </tr>
              <tr>
                <td> optional </td>
                <td> drop if missing at any start attempt </td>
              </tr>
            </table>
          </dd>
4819
          <dt><code>pci</code></dt>
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4820 4821
          <dd>PCI devices can only be described by their <code>address</code>.
          </dd>
4822
          <dt><code>scsi</code></dt>
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4823
          <dd>SCSI devices are described by both the <code>adapter</code>
4824 4825 4826 4827 4828 4829 4830 4831
            and <code>address</code> elements. The <code>address</code>
            element includes a <code>bus</code> attribute (a 2-digit bus
            number), a <code>target</code> attribute (a 10-digit target
            number), and a <code>unit</code> attribute (a 20-digit unit
            number on the bus). Not all hypervisors support larger
            <code>target</code> and <code>unit</code> values. It is up
            to each hypervisor to determine the maximum value supported
            for the adapter.
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4832 4833 4834 4835 4836 4837 4838 4839 4840 4841
            <p>
            <span class="since">Since 1.2.8</span>, the <code>source</code>
            element of a SCSI device may contain the <code>protocol</code>
            attribute. When the attribute is set to "iscsi", the host
            device XML follows the network <a href="#elementsDisks">disk</a>
            device using the same <code>name</code> attribute and optionally
            using the <code>auth</code> element to provide the authentication
            credentials to the iSCSI server.
            </p>
          </dd>
4842 4843 4844 4845 4846 4847 4848
          <dt><code>scsi_host</code></dt>
          <dd><span class="since">Since 2.5.0</span>, multiple LUNs behind a
            single SCSI HBA are described by a <code>protocol</code>
            attribute set to "vhost" and a <code>wwpn</code> attribute that
            is the vhost_scsi wwpn (16 hexadecimal digits with a prefix of
            "naa.") established in the host configfs.
          </dd>
4849 4850 4851 4852 4853 4854
          <dt><code>mdev</code></dt>
          <dd>Mediated devices (<span class="since">Since 3.2.0</span>) are
            described by the <code>address</code> element. The
            <code>address</code> element contains a single mandatory attribute
            <code>uuid</code>.
          </dd>
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4855
        </dl>
4856
      </dd>
4857 4858 4859 4860 4861
      <dt><code>vendor</code>, <code>product</code></dt>
      <dd>The <code>vendor</code> and <code>product</code> elements each have an
      <code>id</code> attribute that specifies the USB vendor and product id.
      The ids can be given in decimal, hexadecimal (starting with 0x) or
      octal (starting with 0) form.</dd>
4862 4863 4864 4865 4866 4867
      <dt><code>boot</code></dt>
      <dd>Specifies that the device is bootable. The <code>order</code>
      attribute determines the order in which devices will be tried during
      boot sequence. The per-device <code>boot</code> elements cannot be
      used together with general boot elements in
      <a href="#elementsOSBIOS">BIOS bootloader</a> section.
4868 4869
      <span class="since">Since 0.8.8</span> for PCI devices,
      <span class="since">Since 1.0.1</span> for USB devices.
4870
      </dd>
4871 4872
      <dt><code>rom</code></dt>
      <dd>The <code>rom</code> element is used to change how a PCI
4873
        device's ROM is presented to the guest. The optional <code>bar</code>
4874 4875 4876 4877 4878 4879 4880
        attribute can be set to "on" or "off", and determines whether
        or not the device's ROM will be visible in the guest's memory
        map. (In PCI documentation, the "rombar" setting controls the
        presence of the Base Address Register for the ROM). If no rom
        bar is specified, the qemu default will be used (older
        versions of qemu used a default of "off", while newer qemus
        have a default of "on"). <span class="since">Since
4881
        0.9.7 (QEMU and KVM only)</span>. The optional
4882
        <code>file</code> attribute contains an absolute path to a binary file
4883 4884 4885 4886 4887
        to be presented to the guest as the device's ROM BIOS. This
        can be useful, for example, to provide a PXE boot ROM for a
        virtual function of an sr-iov capable ethernet device (which
        has no boot ROMs for the VFs).
        <span class="since">Since 0.9.10 (QEMU and KVM only)</span>.
4888 4889 4890 4891 4892 4893
        The optional <code>enabled</code> attribute can be set to
        <code>no</code> to disable PCI ROM loading completely for the device;
        if PCI ROM loading is disabled through this attribute, attempts to
        tweak the loading process further using the <code>bar</code> or
        <code>file</code> attributes will be rejected.
        <span class="since">Since 4.3.0 (QEMU and KVM only)</span>.
4894
      </dd>
4895
      <dt><code>address</code></dt>
4896 4897 4898 4899 4900
      <dd>The <code>address</code> element for USB devices has a
      <code>bus</code> and <code>device</code> attribute to specify the
      USB bus and device number the device appears at on the host.
      The values of these attributes can be given in decimal, hexadecimal
      (starting with 0x) or octal (starting with 0) form.
4901
      For PCI devices the element carries 4 attributes allowing to designate
4902
      the device as can be found with the <code>lspci</code> or
4903
      with <code>virsh nodedev-list</code>. For SCSI devices a 'drive'
4904 4905 4906 4907
      address type must be used. For mediated devices, which are software-only
      devices defining an allocation of resources on the physical parent device,
      the address type used must conform to the <code>model</code> attribute
      of element <code>hostdev</code>, e.g. any address type other than PCI for
4908 4909
      <code>vfio-pci</code> device API or any address type other than CCW for
      <code>vfio-ccw</code> device API will result in an error.
4910 4911
      <a href="#elementsAddress">See above</a> for more details on the address
      element.</dd>
4912 4913 4914 4915 4916 4917 4918
      <dt><code>driver</code></dt>
      <dd>
        PCI devices can have an optional <code>driver</code>
        subelement that specifies which backend driver to use for PCI
        device assignment. Use the <code>name</code> attribute to
        select either "vfio" (for the new VFIO device assignment
        backend, which is compatible with UEFI SecureBoot) or "kvm"
4919
        (the legacy device assignment handled directly by the KVM
4920
        kernel module)<span class="since">Since 1.0.5 (QEMU and KVM
4921 4922 4923 4924 4925 4926 4927 4928
        only, requires kernel 3.6 or newer)</span>. When specified,
        device assignment will fail if the requested method of device
        assignment isn't available on the host. When not specified,
        the default is "vfio" on systems where the VFIO driver is
        available and loaded, and "kvm" on older systems, or those
        where the VFIO driver hasn't been
        loaded <span class="since">Since 1.1.3</span> (prior to that
        the default was always "kvm").
4929
      </dd>
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4930 4931 4932 4933
      <dt><code>readonly</code></dt>
      <dd>Indicates that the device is readonly, only supported by SCSI host
        device now. <span class="since">Since 1.0.6 (QEMU and KVM only)</span>
      </dd>
4934 4935 4936 4937 4938
      <dt><code>shareable</code></dt>
      <dd>If present, this indicates the device is expected to be shared
        between domains (assuming the hypervisor and OS support this).
        Only supported by SCSI host device.
        <span class="since">Since 1.0.6</span>
4939 4940 4941 4942 4943
        <p>
          Note: Although <code>shareable</code> was introduced
          <span class="since">in 1.0.6</span>, it did not work as
          as expected until <span class="since">1.2.2</span>.
        </p>
4944
      </dd>
4945 4946
    </dl>

4947

4948
    <h5><a id="elementsHostDevCaps">Block / character devices</a></h5>
4949 4950 4951 4952

    <p>
      Block / character devices from the host can be passed through
      to the guest using the <code>hostdev</code> element. This is
4953 4954
      only possible with container based virtualization. Devices are specified
      by a fully qualified path.
4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974
      <span class="since">since after 1.0.1 for LXC</span>:
    </p>

    <pre>
...
&lt;hostdev mode='capabilities' type='storage'&gt;
  &lt;source&gt;
    &lt;block&gt;/dev/sdf1&lt;/block&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
...
    </pre>

    <pre>
...
&lt;hostdev mode='capabilities' type='misc'&gt;
  &lt;source&gt;
    &lt;char&gt;/dev/input/event3&lt;/char&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
4975 4976 4977
...
    </pre>

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4978
    <pre>
4979 4980 4981 4982 4983 4984
...
&lt;hostdev mode='capabilities' type='net'&gt;
  &lt;source&gt;
    &lt;interface&gt;eth0&lt;/interface&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
4985 4986 4987 4988 4989 4990 4991
...
    </pre>

    <dl>
      <dt><code>hostdev</code></dt>
      <dd>The <code>hostdev</code> element is the main container for describing
        host devices. For block/character device passthrough <code>mode</code> is
4992 4993
        always "capabilities" and <code>type</code> is "storage" for a block
        device, "misc" for a character device and "net" for a host network
4994
        interface.
4995 4996 4997 4998 4999
      </dd>
      <dt><code>source</code></dt>
      <dd>The source element describes the device as seen from the host.
        For block devices, the path to the block device in the host
        OS is provided in the nested "block" element, while for character
5000 5001
        devices the "char" element is used. For network interfaces, the
        name of the interface is provided in the "interface" element.
5002 5003 5004
      </dd>
    </dl>

5005
    <h4><a id="elementsRedir">Redirected devices</a></h4>
5006 5007 5008 5009 5010 5011 5012 5013

    <p>
      USB device redirection through a character device is
      supported <span class="since">since after 0.9.5 (KVM
      only)</span>:
    </p>

<pre>
5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025
...
&lt;devices&gt;
  &lt;redirdev bus='usb' type='tcp'&gt;
    &lt;source mode='connect' host='localhost' service='4000'/&gt;
    &lt;boot order='1'/&gt;
  &lt;/redirdev&gt;
  &lt;redirfilter&gt;
    &lt;usbdev class='0x08' vendor='0x1234' product='0xbeef' version='2.56' allow='yes'/&gt;
    &lt;usbdev allow='no'/&gt;
  &lt;/redirfilter&gt;
&lt;/devices&gt;
...</pre>
5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039

    <dl>
      <dt><code>redirdev</code></dt>
      <dd>The <code>redirdev</code> element is the main container for
        describing redirected devices. <code>bus</code> must be "usb"
        for a USB device.

        An additional attribute <code>type</code> is required,
        matching one of the
        supported <a href="#elementsConsole">serial device</a> types,
        to describe the host side of the
        tunnel; <code>type='tcp'</code>
        or <code>type='spicevmc'</code> (which uses the usbredir
        channel of a <a href="#elementsGraphics">SPICE graphics
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5040 5041
        device</a>) are typical. The redirdev element has an optional
        sub-element <code>&lt;address&gt;</code> which can tie the
5042 5043 5044 5045
        device to a particular controller. Further sub-elements,
        such as <code>&lt;source&gt;</code>, may be required according
        to the given type, although a <code>&lt;target&gt;</code> sub-element
        is not required (since the consumer of the character device is
5046 5047 5048 5049 5050 5051 5052 5053 5054 5055
        the hypervisor itself, rather than a device visible in the guest).
      </dd>
      <dt><code>boot</code></dt>

      <dd>Specifies that the device is bootable.
        The <code>order</code> attribute determines the order in which
        devices will be tried during boot sequence. The per-device
        <code>boot</code> elements cannot be used together with general
        boot elements in  <a href="#elementsOSBIOS">BIOS bootloader</a> section.
        (<span class="since">Since 1.0.1</span>)
5056 5057 5058 5059
      </dd>
      <dt><code>redirfilter</code></dt>
      <dd>The<code> redirfilter </code>element is used for creating the
        filter rule to filter out certain devices from redirection.
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5060 5061
        It uses sub-element <code>&lt;usbdev&gt;</code> to define each filter rule.
        <code>class</code> attribute is the USB Class code, for example,
5062
        0x08 represents mass storage devices. The USB device can be addressed by
J
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5063
        vendor / product id using the <code>vendor</code> and <code>product</code> attributes.
5064 5065
        <code>version</code> is the device revision from the bcdDevice field (not
        the version of the USB protocol).
5066
        These four attributes are optional and <code>-1</code> can be used to allow
J
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5067
        any value for them. <code>allow</code> attribute is mandatory,
5068 5069
        'yes' means allow, 'no' for deny.
      </dd>
5070 5071
    </dl>

5072
    <h4><a id="elementsSmartcard">Smartcard devices</a></h4>
5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087

    <p>
      A virtual smartcard device can be supplied to the guest via the
      <code>smartcard</code> element. A USB smartcard reader device on
      the host cannot be used on a guest with simple device
      passthrough, since it will then not be available on the host,
      possibly locking the host computer when it is "removed".
      Therefore, some hypervisors provide a specialized virtual device
      that can present a smartcard interface to the guest, with
      several modes for describing how credentials are obtained from
      the host or even a from a channel created to a third-party
      smartcard provider. <span class="since">Since 0.8.8</span>
    </p>

<pre>
5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104
...
&lt;devices&gt;
  &lt;smartcard mode='host'/&gt;
  &lt;smartcard mode='host-certificates'&gt;
    &lt;certificate&gt;cert1&lt;/certificate&gt;
    &lt;certificate&gt;cert2&lt;/certificate&gt;
    &lt;certificate&gt;cert3&lt;/certificate&gt;
    &lt;database&gt;/etc/pki/nssdb/&lt;/database&gt;
  &lt;/smartcard&gt;
  &lt;smartcard mode='passthrough' type='tcp'&gt;
    &lt;source mode='bind' host='127.0.0.1' service='2001'/&gt;
    &lt;protocol type='raw'/&gt;
    &lt;address type='ccid' controller='0' slot='0'/&gt;
  &lt;/smartcard&gt;
  &lt;smartcard mode='passthrough' type='spicevmc'/&gt;
&lt;/devices&gt;
...
5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115
</pre>

    <p>
      The <code>&lt;smartcard&gt;</code> element has a mandatory
      attribute <code>mode</code>.  The following modes are supported;
      in each mode, the guest sees a device on its USB bus that
      behaves like a physical USB CCID (Chip/Smart Card Interface
      Device) card.
    </p>

    <dl>
5116
      <dt><code>host</code></dt>
5117 5118 5119 5120 5121 5122
      <dd>The simplest operation, where the hypervisor relays all
      requests from the guest into direct access to the host's
      smartcard via NSS.  No other attributes or sub-elements are
      required.  See below about the use of an
      optional <code>&lt;address&gt;</code> sub-element.</dd>

5123
      <dt><code>host-certificates</code></dt>
5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136
      <dd>Rather than requiring a smartcard to be plugged into the
      host, it is possible to provide three NSS certificate names
      residing in a database on the host.  These certificates can be
      generated via the command <code>certutil -d /etc/pki/nssdb -x -t
      CT,CT,CT -S -s CN=cert1 -n cert1</code>, and the resulting three
      certificate names must be supplied as the content of each of
      three <code>&lt;certificate&gt;</code> sub-elements.  An
      additional sub-element <code>&lt;database&gt;</code> can specify
      the absolute path to an alternate directory (matching
      the <code>-d</code> option of the <code>certutil</code> command
      when creating the certificates); if not present, it defaults to
      /etc/pki/nssdb.</dd>

5137
      <dt><code>passthrough</code></dt>
5138 5139 5140 5141 5142 5143 5144
      <dd>Rather than having the hypervisor directly communicate with
      the host, it is possible to tunnel all requests through a
      secondary character device to a third-party provider (which may
      in turn be talking to a smartcard or using three certificate
      files).  In this mode of operation, an additional
      attribute <code>type</code> is required, matching one of the
      supported <a href="#elementsConsole">serial device</a> types, to
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5145 5146 5147 5148 5149
      describe the host side of the tunnel; <code>type='tcp'</code>
      or <code>type='spicevmc'</code> (which uses the smartcard
      channel of a <a href="#elementsGraphics">SPICE graphics
      device</a>) are typical.  Further sub-elements, such
      as <code>&lt;source&gt;</code>, may be required according to the
5150 5151 5152 5153 5154 5155 5156 5157 5158
      given type, although a <code>&lt;target&gt;</code> sub-element
      is not required (since the consumer of the character device is
      the hypervisor itself, rather than a device visible in the
      guest).</dd>
    </dl>

    <p>
      Each mode supports an optional
      sub-element <code>&lt;address&gt;</code>, which fine-tunes the
5159 5160 5161
      correlation between the smartcard and a ccid bus
      controller, <a href="#elementsAddress">documented above</a>.
      For now, qemu only supports at most one
5162 5163 5164
      smartcard, with an address of bus=0 slot=0.
    </p>

5165
    <h4><a id="elementsNICS">Network interfaces</a></h4>
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5166

5167
<pre>
5168 5169 5170 5171 5172 5173 5174 5175 5176 5177
...
&lt;devices&gt;
  &lt;interface type='direct' trustGuestRxFilters='yes'&gt;
    &lt;source dev='eth0'/&gt;
    &lt;mac address='52:54:00:5d:c7:9e'/&gt;
    &lt;boot order='1'/&gt;
    &lt;rom bar='off'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
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5179 5180 5181
    <p>
      There are several possibilities for specifying a network
      interface visible to the guest.  Each subsection below provides
5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193
      more details about common setup options.
    </p>
    <p>
      <span class="since">Since 1.2.10</span>),
      the <code>interface</code> element
      property <code>trustGuestRxFilters</code> provides the
      capability for the host to detect and trust reports from the
      guest regarding changes to the interface mac address and receive
      filters by setting the attribute to <code>yes</code>. The default
      setting for the attribute is <code>no</code> for security
      reasons and support depends on the guest network device model as
      well as the type of connection on the host - currently it is
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      only supported for the virtio device model and for macvtap
5195 5196 5197 5198
      connections on the host.
    </p>
    <p>
      Each <code>&lt;interface&gt;</code> element has an
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      optional <code>&lt;address&gt;</code> sub-element that can tie
      the interface to a particular pci slot, with
5201 5202
      attribute <code>type='pci'</code>
      as <a href="#elementsAddress">documented above</a>.
E
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    </p>

5205
    <h5><a id="elementsNICSVirtual">Virtual network</a></h5>
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    <p>
      <strong><em>
      This is the recommended config for general guest connectivity on
5210 5211 5212 5213
      hosts with dynamic / wireless networking configs (or multi-host
      environments where the host hardware details are described
      separately in a <code>&lt;network&gt;</code>
      definition <span class="since">Since 0.9.4</span>).
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      </em></strong>
    </p>

    <p>
5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244

      Provides a connection whose details are described by the named
      network definition. Depending on the virtual network's "forward
      mode" configuration, the network may be totally isolated
      (no <code>&lt;forward&gt;</code> element given), NAT'ing to an
      explicit network device or to the default route
      (<code>&lt;forward mode='nat'&gt;</code>), routed with no NAT
      (<code>&lt;forward mode='route'/&gt;</code>), or connected
      directly to one of the host's network interfaces (via macvtap)
      or bridge devices ((<code>&lt;forward
      mode='bridge|private|vepa|passthrough'/&gt;</code> <span class="since">Since
      0.9.4</span>)
    </p>
    <p>
      For networks with a forward mode of bridge, private, vepa, and
      passthrough, it is assumed that the host has any necessary DNS
      and DHCP services already setup outside the scope of libvirt. In
      the case of isolated, nat, and routed networks, DHCP and DNS are
      provided on the virtual network by libvirt, and the IP range can
      be determined by examining the virtual network config with
      '<code>virsh net-dumpxml [networkname]</code>'. There is one
      virtual network called 'default' setup out of the box which does
      NAT'ing to the default route and has an IP range
      of <code>192.168.122.0/255.255.255.0</code>. Each guest will
      have an associated tun device created with a name of vnetN,
      which can also be overridden with the &lt;target&gt; element
      (see
5245
      <a href="#elementsNICSTargetOverride">overriding the target element</a>).
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    </p>
5247 5248 5249 5250 5251 5252
    <p>
      When the source of an interface is a network,
      a <code>portgroup</code> can be specified along with the name of
      the network; one network may have multiple portgroups defined,
      with each portgroup containing slightly different configuration
      information for different classes of network
5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271
      connections. <span class="since">Since 0.9.4</span>.
    </p>
    <p>
      Also, similar to <code>direct</code> network connections
      (described below), a connection of type <code>network</code> may
      specify a <code>virtualport</code> element, with configuration
      data to be forwarded to a vepa (802.1Qbg) or 802.1Qbh compliant
      switch (<span class="since">Since 0.8.2</span>), or to an
      Open vSwitch virtual switch (<span class="since">Since
      0.9.11</span>).
    </p>
    <p>
      Since the actual type of switch may vary depending on the
      configuration in the <code>&lt;network&gt;</code> on the host,
      it is acceptable to omit the virtualport <code>type</code>
      attribute, and specify attributes from multiple different
      virtualport types (and also to leave out certain attributes); at
      domain startup time, a complete <code>&lt;virtualport&gt;</code>
      element will be constructed by merging together the type and
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      attributes defined in the network and the portgroup referenced
      by the interface. The newly-constructed virtualport is a combination
      of them. The attributes from lower virtualport can't make change
      on the ones defined in higher virtualport.
      Interface takes the highest priority, portgroup is lowest priority.
5277 5278 5279
      (<span class="since">Since 0.10.0</span>). For example, in order
      to work properly with both an 802.1Qbh switch and an Open vSwitch
      switch, you may choose to specify no type, but both
V
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      a <code>profileid</code> (in case the switch is 802.1Qbh) and
5281 5282 5283 5284 5285 5286 5287 5288 5289
      an <code>interfaceid</code> (in case the switch is Open vSwitch)
      (you may also omit the other attributes, such as managerid,
      typeid, or profileid, to be filled in from the
      network's <code>&lt;virtualport&gt;</code>). If you want to
      limit a guest to connecting only to certain types of switches,
      you can specify the virtualport type, but still omit some/all of
      the parameters - in this case if the host's network has a
      different type of virtualport, connection of the interface will
      fail.
5290
    </p>
D
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5291

5292
<pre>
5293 5294 5295 5296 5297
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
  &lt;/interface&gt;
5298
  ...
5299 5300 5301 5302 5303 5304 5305 5306 5307 5308
  &lt;interface type='network'&gt;
    &lt;source network='default' portgroup='engineering'/&gt;
    &lt;target dev='vnet7'/&gt;
    &lt;mac address="00:11:22:33:44:55"/&gt;
    &lt;virtualport&gt;
      &lt;parameters instanceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
D
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5309

5310
    <h5><a id="elementsNICSBridge">Bridge to LAN</a></h5>
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5311 5312 5313 5314

    <p>
      <strong><em>
      This is the recommended config for general guest connectivity on
5315
      hosts with static wired networking configs.
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5316 5317 5318 5319
      </em></strong>
    </p>

    <p>
E
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      Provides a bridge from the VM directly to the LAN. This assumes
D
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      there is a bridge device on the host which has one or more of the hosts
      physical NICs enslaved. The guest VM will have an associated tun device
      created with a name of vnetN, which can also be overridden with the
5324 5325 5326 5327 5328
      &lt;target&gt; element (see
      <a href="#elementsNICSTargetOverride">overriding the target element</a>).
      The tun device will be enslaved to the bridge. The IP range / network
      configuration is whatever is used on the LAN. This provides the guest VM
      full incoming &amp; outgoing net access just like a physical machine.
D
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    </p>
5330 5331 5332
    <p>
      On Linux systems, the bridge device is normally a standard Linux
      host bridge. On hosts that support Open vSwitch, it is also
5333
      possible to connect to an Open vSwitch bridge device by adding
5334 5335 5336 5337 5338 5339
      a <code>&lt;virtualport type='openvswitch'/&gt;</code> to the
      interface definition.  (<span class="since">Since
      0.9.11</span>). The Open vSwitch type virtualport accepts two
      parameters in its <code>&lt;parameters&gt;</code> element -
      an <code>interfaceid</code> which is a standard uuid used to
      uniquely identify this particular interface to Open vSwitch (if
C
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5340
      you do not specify one, a random interfaceid will be generated
5341 5342 5343 5344
      for you when you first define the interface), and an
      optional <code>profileid</code> which is sent to Open vSwitch as
      the interfaces "port-profile".
    </p>
5345
<pre>
5346 5347
...
&lt;devices&gt;
5348
  ...
5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365
  &lt;interface type='bridge'&gt;
    &lt;source bridge='br0'/&gt;
  &lt;/interface&gt;
  &lt;interface type='bridge'&gt;
    &lt;source bridge='br1'/&gt;
    &lt;target dev='vnet7'/&gt;
    &lt;mac address="00:11:22:33:44:55"/&gt;
  &lt;/interface&gt;
  &lt;interface type='bridge'&gt;
    &lt;source bridge='ovsbr'/&gt;
    &lt;virtualport type='openvswitch'&gt;
      &lt;parameters profileid='menial' interfaceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
  ...
&lt;/devices&gt;
...</pre>
5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379

    <p>
      On hosts that support Open vSwitch on the kernel side and have the
      Midonet Host Agent configured, it is also possible to connect to the
      'midonet' bridge device by adding a
      <code>&lt;virtualport type='midonet'/&gt;</code> to the
      interface definition.  (<span class="since">Since
      1.2.13</span>). The Midonet virtualport type requires an
      <code>interfaceid</code> attribute in its
      <code>&lt;parameters&gt;</code> element. This interface id is the UUID
      that specifies which port in the virtual network topology will be bound
      to the interface.
    </p>
<pre>
5380 5381
...
&lt;devices&gt;
5382
  ...
5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399
  &lt;interface type='bridge'&gt;
    &lt;source bridge='br0'/&gt;
  &lt;/interface&gt;
  &lt;interface type='bridge'&gt;
    &lt;source bridge='br1'/&gt;
    &lt;target dev='vnet7'/&gt;
    &lt;mac address="00:11:22:33:44:55"/&gt;
  &lt;/interface&gt;
  &lt;interface type='bridge'&gt;
    &lt;source bridge='midonet'/&gt;
    &lt;virtualport type='midonet'&gt;
      &lt;parameters interfaceid='0b2d64da-3d0e-431e-afdd-804415d6ebbb'/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
  ...
&lt;/devices&gt;
...</pre>
D
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5400

5401
    <h5><a id="elementsNICSSlirp">Userspace SLIRP stack</a></h5>
D
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5402 5403 5404 5405 5406 5407 5408

    <p>
      Provides a virtual LAN with NAT to the outside world. The virtual
      network has DHCP &amp; DNS services and will give the guest VM addresses
      starting from <code>10.0.2.15</code>. The default router will be
      <code>10.0.2.2</code> and the DNS server will be <code>10.0.2.3</code>.
      This networking is the only option for unprivileged users who need their
5409 5410 5411 5412 5413 5414 5415 5416 5417
      VMs to have outgoing access. <span class="since">Since 3.8.0</span>
      it is possible to override the default network address by
      including an <code>ip</code> element specifying an IPv4
      address in its one mandatory attribute, <code>address</code>.
      Optionally, a second <code>ip</code> element with a
      <code>family</code> attribute set to "ipv6" can be
      specified to add an IPv6 address to the interface.
      <code>address</code>. Optionally, address
      <code>prefix</code> can be specified.
D
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5418 5419
    </p>

5420
<pre>
5421 5422 5423
...
&lt;devices&gt;
  &lt;interface type='user'/&gt;
5424
  ...
5425 5426
  &lt;interface type='user'&gt;
    &lt;mac address="00:11:22:33:44:55"/&gt;
5427 5428
    &lt;ip family='ipv4' address='172.17.2.0' prefix='24'/&gt;
    &lt;ip family='ipv6' address='2001:db8:ac10:fd01::' prefix='64'/&gt;
5429 5430 5431
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
D
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5432 5433


5434
    <h5><a id="elementsNICSEthernet">Generic ethernet connection</a></h5>
D
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5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445

    <p>
      Provides a means for the administrator to execute an arbitrary script
      to connect the guest's network to the LAN. The guest will have a tun
      device created with a name of vnetN, which can also be overridden with the
      &lt;target&gt; element. After creating the tun device a shell script will
      be run which is expected to do whatever host network integration is
      required. By default this script is called /etc/qemu-ifup but can be
      overridden.
    </p>

5446
<pre>
5447 5448 5449
...
&lt;devices&gt;
  &lt;interface type='ethernet'/&gt;
5450
  ...
5451 5452 5453 5454 5455 5456
  &lt;interface type='ethernet'&gt;
    &lt;target dev='vnet7'/&gt;
    &lt;script path='/etc/qemu-ifup-mynet'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
D
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5457

5458
    <h5><a id="elementsNICSDirect">Direct attachment to physical interface</a></h5>
5459 5460 5461

    <p>
      Provides direct attachment of the virtual machine's NIC to the given
5462
      physical interface of the host.
E
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5463
      <span class="since">Since 0.7.7 (QEMU and KVM only)</span><br/>
5464 5465 5466
      This setup requires the Linux macvtap
      driver to be available. <span class="since">(Since Linux 2.6.34.)</span>
      One of the modes 'vepa'
5467
      ( <a href="http://www.ieee802.org/1/files/public/docs2009/new-evb-congdon-vepa-modular-0709-v01.pdf">
5468
      'Virtual Ethernet Port Aggregator'</a>), 'bridge' or 'private'
5469
      can be chosen for the operation mode of the macvtap device, 'vepa'
5470 5471
      being the default mode. The individual modes cause the delivery of
      packets to behave as follows:
5472
    </p>
5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484
    <p>
      If the model type is set to <code>virtio</code> and
      interface's <code>trustGuestRxFilters</code> attribute is set
      to <code>yes</code>, changes made to the interface mac address,
      unicast/multicast receive filters, and vlan settings in the
      guest will be monitored and propagated to the associated macvtap
      device on the host (<span class="since">Since
      1.2.10</span>). If <code>trustGuestRxFilters</code> is not set,
      or is not supported for the device model in use, an attempted
      change to the mac address originating from the guest side will
      result in a non-working network connection.
    </p>
5485

5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496
    <dl>
      <dt><code>vepa</code></dt>
      <dd>All VMs' packets are sent to the external bridge. Packets
      whose destination is a VM on the same host as where the
      packet originates from are sent back to the host by the VEPA
      capable bridge (today's bridges are typically not VEPA capable).</dd>
      <dt><code>bridge</code></dt>
      <dd>Packets whose destination is on the same host as where they
      originate from are directly delivered to the target macvtap device.
      Both origin and destination devices need to be in bridge mode
      for direct delivery. If either one of them is in <code>vepa</code> mode,
E
Eric Blake 已提交
5497
      a VEPA capable bridge is required.</dd>
5498 5499 5500 5501 5502 5503
      <dt><code>private</code></dt>
      <dd>All packets are sent to the external bridge and will only be
      delivered to a target VM on the same host if they are sent through an
      external router or gateway and that device sends them back to the
      host. This procedure is followed if either the source or destination
      device is in <code>private</code> mode.</dd>
5504 5505 5506 5507 5508 5509 5510
      <dt><code>passthrough</code></dt>
      <dd>This feature attaches a virtual function of a SRIOV capable
      NIC directly to a VM without losing the migration capability.
      All packets are sent to the VF/IF of the configured network device.
      Depending on the capabilities of the device additional prerequisites or
      limitations may apply; for example, on Linux this requires
      kernel 2.6.38 or newer. <span class="since">Since 0.9.2</span></dd>
5511 5512
    </dl>

5513
<pre>
5514 5515
...
&lt;devices&gt;
5516
  ...
5517 5518 5519 5520 5521
  &lt;interface type='direct' trustGuestRxFilters='no'&gt;
    &lt;source dev='eth0' mode='vepa'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5522

5523 5524 5525 5526
    <p>
      The network access of direct attached virtual machines can be
      managed by the hardware switch to which the physical interface
      of the host machine is connected to.
E
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5527
    </p>
5528 5529 5530 5531 5532 5533 5534
    <p>
      The interface can have additional parameters as shown below,
      if the switch is conforming to the IEEE 802.1Qbg standard.
      The parameters of the virtualport element are documented in more detail
      in the IEEE 802.1Qbg standard. The values are network specific and
      should be provided by the network administrator. In 802.1Qbg terms,
      the Virtual Station Interface (VSI) represents the virtual interface
5535
      of a virtual machine. <span class="since">Since 0.8.2</span>
5536
    </p>
5537 5538 5539 5540
    <p>
      Please note that IEEE 802.1Qbg requires a non-zero value for the
      VLAN ID.
    </p>
5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561
    <dl>
      <dt><code>managerid</code></dt>
      <dd>The VSI Manager ID identifies the database containing the VSI type
        and instance definitions. This is an integer value and the
        value 0 is reserved.</dd>
      <dt><code>typeid</code></dt>
      <dd>The VSI Type ID identifies a VSI type characterizing the network
        access. VSI types are typically managed by network administrator.
        This is an integer value.
      </dd>
      <dt><code>typeidversion</code></dt>
      <dd>The VSI Type Version allows multiple versions of a VSI Type.
        This is an integer value.
      </dd>
      <dt><code>instanceid</code></dt>
      <dd>The VSI Instance ID Identifier is generated when a VSI instance
        (i.e. a virtual interface of a virtual machine) is created.
        This is a globally unique identifier.
      </dd>
    </dl>
<pre>
5562 5563
...
&lt;devices&gt;
5564
  ...
5565 5566 5567 5568 5569 5570 5571 5572
  &lt;interface type='direct'&gt;
    &lt;source dev='eth0.2' mode='vepa'/&gt;
    &lt;virtualport type="802.1Qbg"&gt;
      &lt;parameters managerid="11" typeid="1193047" typeidversion="2" instanceid="09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f"/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5573

5574 5575 5576 5577 5578 5579 5580 5581 5582
    <p>
      The interface can have additional parameters as shown below
      if the switch is conforming to the IEEE 802.1Qbh standard.
      The values are network specific and should be provided by the
      network administrator. <span class="since">Since 0.8.2</span>
    </p>
    <dl>
      <dt><code>profileid</code></dt>
      <dd>The profile ID contains the name of the port profile that is to
E
Eric Blake 已提交
5583
        be applied to this interface.  This name is resolved by the port
5584 5585 5586 5587 5588
        profile database into the network parameters from the port profile,
        and those network parameters will be applied to this interface.
      </dd>
    </dl>
  <pre>
5589 5590
...
&lt;devices&gt;
5591
  ...
5592 5593 5594 5595 5596 5597 5598 5599 5600
  &lt;interface type='direct'&gt;
    &lt;source dev='eth0' mode='private'/&gt;
    &lt;virtualport type='802.1Qbh'&gt;
      &lt;parameters profileid='finance'/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...
</pre>
5601

5602

5603
    <h5><a id="elementsNICSHostdev">PCI Passthrough</a></h5>
5604 5605 5606 5607 5608 5609

    <p>
      A PCI network device (specified by the &lt;source&gt; element)
      is directly assigned to the guest using generic device
      passthrough, after first optionally setting the device's MAC
      address to the configured value, and associating the device with
5610
      an 802.1Qbh capable switch using an optionally specified
5611
      &lt;virtualport&gt; element (see the examples of virtualport
5612 5613 5614 5615 5616 5617 5618 5619 5620
      given above for type='direct' network devices). Note that - due
      to limitations in standard single-port PCI ethernet card driver
      design - only SR-IOV (Single Root I/O Virtualization) virtual
      function (VF) devices can be assigned in this manner; to assign
      a standard single-port PCI or PCIe ethernet card to a guest, use
      the traditional &lt;hostdev&gt; device definition and
      <span class="since">Since 0.9.11</span>
    </p>

5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632
    <p>
      To use VFIO device assignment rather than traditional/legacy KVM
      device assignment (VFIO is a new method of device assignment
      that is compatible with UEFI Secure Boot), a type='hostdev'
      interface can have an optional <code>driver</code> sub-element
      with a <code>name</code> attribute set to "vfio". To use legacy
      KVM device assignment you can set <code>name</code> to "kvm" (or
      simply omit the <code>&lt;driver&gt;</code> element, since "kvm"
      is currently the default).
      <span class="since">Since 1.0.5 (QEMU and KVM only, requires kernel 3.6 or newer)</span>
    </p>

5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646
    <p>
      Note that this "intelligent passthrough" of network devices is
      very similar to the functionality of a standard &lt;hostdev&gt;
      device, the difference being that this method allows specifying
      a MAC address and &lt;virtualport&gt; for the passed-through
      device. If these capabilities are not required, if you have a
      standard single-port PCI, PCIe, or USB network card that doesn't
      support SR-IOV (and hence would anyway lose the configured MAC
      address during reset after being assigned to the guest domain),
      or if you are using a version of libvirt older than 0.9.11, you
      should use standard &lt;hostdev&gt; to assign the device to the
      guest instead of &lt;interface type='hostdev'/&gt;.
    </p>

5647 5648 5649 5650 5651 5652
    <p>
      Similar to the functionality of a standard &lt;hostdev&gt; device,
      when <code>managed</code> is "yes", it is detached from the host
      before being passed on to the guest, and reattached to the host
      after the guest exits. If <code>managed</code> is omitted or "no",
      the user is responsible to call <code>virNodeDeviceDettach</code>
J
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5653
      (or <code>virsh nodedev-detach</code>) before starting the guest
5654 5655 5656 5657 5658
      or hot-plugging the device, and <code>virNodeDeviceReAttach</code>
      (or <code>virsh nodedev-reattach</code>) after hot-unplug or
      stopping the guest.
    </p>

5659
<pre>
5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673
...
&lt;devices&gt;
  &lt;interface type='hostdev' managed='yes'&gt;
    &lt;driver name='vfio'/&gt;
    &lt;source&gt;
      &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/&gt;
    &lt;/source&gt;
    &lt;mac address='52:54:00:6d:90:02'/&gt;
    &lt;virtualport type='802.1Qbh'&gt;
      &lt;parameters profileid='finance'/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5674 5675


5676
    <h5><a id="elementsNICSMulticast">Multicast tunnel</a></h5>
D
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5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687 5688 5689

    <p>
      A multicast group is setup to represent a virtual network. Any VMs
      whose network devices are in the same multicast group can talk to each
      other even across hosts. This mode is also available to unprivileged
      users. There is no default DNS or DHCP support and no outgoing network
      access. To provide outgoing network access, one of the VMs should have a
      2nd NIC which is connected to one of the first 4 network types and do the
      appropriate routing. The multicast protocol is compatible with that used
      by user mode linux guests too. The source address used must be from the
      multicast address block.
    </p>

5690
<pre>
5691 5692 5693 5694 5695 5696 5697 5698
...
&lt;devices&gt;
  &lt;interface type='mcast'&gt;
    &lt;mac address='52:54:00:6d:90:01'/&gt;
    &lt;source address='230.0.0.1' port='5558'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
5699

5700
    <h5><a id="elementsNICSTCP">TCP tunnel</a></h5>
D
Daniel P. Berrange 已提交
5701 5702 5703 5704 5705 5706 5707 5708 5709 5710

    <p>
      A TCP client/server architecture provides a virtual network. One VM
      provides the server end of the network, all other VMS are configured as
      clients. All network traffic is routed between the VMs via the server.
      This mode is also available to unprivileged users. There is no default
      DNS or DHCP support and no outgoing network access. To provide outgoing
      network access, one of the VMs should have a 2nd NIC which is connected
      to one of the first 4 network types and do the appropriate routing.</p>

5711
<pre>
5712 5713 5714 5715 5716 5717
...
&lt;devices&gt;
  &lt;interface type='server'&gt;
    &lt;mac address='52:54:00:22:c9:42'/&gt;
    &lt;source address='192.168.0.1' port='5558'/&gt;
  &lt;/interface&gt;
5718
  ...
5719 5720 5721 5722 5723 5724
  &lt;interface type='client'&gt;
    &lt;mac address='52:54:00:8b:c9:51'/&gt;
    &lt;source address='192.168.0.1' port='5558'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5725

5726
    <h5><a id="elementsNICSUDP">UDP unicast tunnel</a></h5>
5727 5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738

    <p>
    A UDP unicast architecture provides a virtual network which enables
    connections between QEMU instances using QEMU's UDP infrastructure.

    The xml "source" address is the endpoint address to which the UDP socket
    packets will be sent from the host running QEMU.
    The xml "local" address is the address of the interface from which the
    UDP socket packets will originate from the QEMU host.
    <span class="since">Since 1.2.20</span></p>

<pre>
5739 5740 5741 5742 5743 5744 5745 5746 5747 5748
...
&lt;devices&gt;
  &lt;interface type='udp'&gt;
    &lt;mac address='52:54:00:22:c9:42'/&gt;
    &lt;source address='127.0.0.1' port='11115'&gt;
      &lt;local address='127.0.0.1' port='11116'/&gt;
    &lt;/source&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
5749

5750
    <h5><a id="elementsNICSModel">Setting the NIC model</a></h5>
5751

5752
<pre>
5753 5754 5755 5756 5757 5758 5759 5760 5761
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet1'/&gt;
    <b>&lt;model type='ne2k_pci'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781

    <p>
      For hypervisors which support this, you can set the model of
      emulated network interface card.
    </p>

    <p>
      The values for <code>type</code> aren't defined specifically by
      libvirt, but by what the underlying hypervisor supports (if
      any).  For QEMU and KVM you can get a list of supported models
      with these commands:
    </p>

<pre>
qemu -net nic,model=? /dev/null
qemu-kvm -net nic,model=? /dev/null
</pre>

    <p>
      Typical values for QEMU and KVM include:
5782 5783 5784 5785 5786
      ne2k_isa i82551 i82557b i82559er ne2k_pci pcnet rtl8139 e1000 virtio.
      <span class="since">Since 5.2.0</span>, <code>virtio-transitional</code>
      and <code>virtio-non-transitional</code> values are supported.
      See <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
      for more details.
5787
    </p>
D
Daniel P. Berrange 已提交
5788

5789
    <h5><a id="elementsDriverBackendOptions">Setting NIC driver-specific options</a></h5>
5790 5791

<pre>
5792 5793 5794 5795 5796 5797
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet1'/&gt;
    &lt;model type='virtio'/&gt;
5798
    <b>&lt;driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5' rx_queue_size='256' tx_queue_size='256'&gt;
5799 5800 5801
      &lt;host csum='off' gso='off' tso4='off' tso6='off' ecn='off' ufo='off' mrg_rxbuf='off'/&gt;
      &lt;guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/&gt;
    &lt;/driver&gt;
5802
    </b>&lt;/interface&gt;
5803 5804
&lt;/devices&gt;
...</pre>
5805 5806 5807 5808 5809 5810 5811 5812 5813

    <p>
      Some NICs may have tunable driver-specific options. These are
      set as attributes of the <code>driver</code> sub-element of the
      interface definition. Currently the following attributes are
      available for the <code>"virtio"</code> NIC driver:
    </p>

    <dl>
5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825
      <dt><code>name</code></dt>
      <dd>
        The optional <code>name</code> attribute forces which type of
        backend driver to use. The value can be either 'qemu' (a
        user-space backend) or 'vhost' (a kernel backend, which
        requires the vhost module to be provided by the kernel); an
        attempt to require the vhost driver without kernel support
        will be rejected.  If this attribute is not present, then the
        domain defaults to 'vhost' if present, but silently falls back
        to 'qemu' without error.
        <span class="since">Since 0.8.8 (QEMU and KVM only)</span>
      </dd>
5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837
      <dd>
        For interfaces of type='hostdev' (PCI passthrough devices)
        the <code>name</code> attribute can optionally be set to
        "vfio" or "kvm". "vfio" tells libvirt to use VFIO device
        assignment rather than traditional KVM device assignment (VFIO
        is a new method of device assignment that is compatible with
        UEFI Secure Boot), and "kvm" tells libvirt to use the legacy
        device assignment performed directly by the kvm kernel module
        (the default is currently "kvm", but is subject to change).
        <span class="since">Since 1.0.5 (QEMU and KVM only, requires
        kernel 3.6 or newer)</span>
      </dd>
5838 5839 5840 5841 5842
      <dd>
        For interfaces of type='vhostuser', the <code>name</code>
        attribute is ignored. The backend driver used is always
        vhost-user.
      </dd>
5843

5844 5845 5846 5847 5848
      <dt><code>txmode</code></dt>
      <dd>
        The <code>txmode</code> attribute specifies how to handle
        transmission of packets when the transmit buffer is full. The
        value can be either 'iothread' or 'timer'.
E
Eric Blake 已提交
5849
        <span class="since">Since 0.8.8 (QEMU and KVM only)</span><br/><br/>
5850 5851 5852 5853

        If set to 'iothread', packet tx is all done in an iothread in
        the bottom half of the driver (this option translates into
        adding "tx=bh" to the qemu commandline -device virtio-net-pci
E
Eric Blake 已提交
5854
        option).<br/><br/>
5855 5856 5857 5858

        If set to 'timer', tx work is done in qemu, and if there is
        more tx data than can be sent at the present time, a timer is
        set before qemu moves on to do other things; when the timer
E
Eric Blake 已提交
5859
        fires, another attempt is made to send more data.<br/><br/>
5860 5861 5862 5863

        The resulting difference, according to the qemu developer who
        added the option is: "bh makes tx more asynchronous and reduces
        latency, but potentially causes more processor bandwidth
5864 5865
        contention since the CPU doing the tx isn't necessarily the
        CPU where the guest generated the packets."<br/><br/>
5866

5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882
        <b>In general you should leave this option alone, unless you
        are very certain you know what you are doing.</b>
      </dd>
      <dt><code>ioeventfd</code></dt>
      <dd>
        This optional attribute allows users to set
        <a href='https://patchwork.kernel.org/patch/43390/'>
        domain I/O asynchronous handling</a> for interface device.
        The default is left to the discretion of the hypervisor.
        Accepted values are "on" and "off". Enabling this allows
        qemu to execute VM while a separate thread handles I/O.
        Typically guests experiencing high system CPU utilization
        during I/O will benefit from this. On the other hand,
        on overloaded host it could increase guest I/O latency.
        <span class="since">Since 0.9.3 (QEMU and KVM only)</span><br/><br/>

5883
        <b>In general you should leave this option alone, unless you
5884 5885 5886 5887 5888 5889
        are very certain you know what you are doing.</b>
      </dd>
      <dt><code>event_idx</code></dt>
      <dd>
        The <code>event_idx</code> attribute controls some aspects of
        device event processing. The value can be either 'on' or 'off'
5890
        - if it is on, it will reduce the number of interrupts and
5891 5892 5893 5894 5895 5896 5897
        exits for the guest. The default is determined by QEMU;
        usually if the feature is supported, default is on. In case
        there is a situation where this behavior is suboptimal, this
        attribute provides a way to force the feature off.
        <span class="since">Since 0.9.5 (QEMU and KVM only)</span><br/><br/>

        <b>In general you should leave this option alone, unless you
5898 5899
        are very certain you know what you are doing.</b>
      </dd>
5900 5901
      <dt><code>queues</code></dt>
      <dd>
5902 5903
        The optional <code>queues</code> attribute controls the number
        of queues to be used for either
5904
        <a href="https://www.linux-kvm.org/page/Multiqueue"> Multiqueue
5905 5906 5907 5908
        virtio-net</a> or <a href="#elementVhostuser">vhost-user</a> network
        interfaces.  Use of multiple packet processing queues requires the
        interface having the <code>&lt;model type='virtio'/&gt;</code>
        element.  Each queue will potentially be handled by a different
5909
        processor, resulting in much higher throughput.
5910
        <span class="since">virtio-net since 1.0.6 (QEMU and KVM only)</span>
5911
        <span class="since">vhost-user since 1.2.17 (QEMU and KVM only)</span>
5912
      </dd>
5913 5914 5915 5916 5917 5918 5919 5920 5921
      <dt><code>rx_queue_size</code></dt>
      <dd>
        The optional <code>rx_queue_size</code> attribute controls
        the size of virtio ring for each queue as described above.
        The default value is hypervisor dependent and may change
        across its releases. Moreover, some hypervisors may pose
        some restrictions on actual value. For instance, latest
        QEMU (as of 2016-09-01) requires value to be a power of two
        from [256, 1024] range.
5922
        <span class="since">Since 2.3.0 (QEMU and KVM only)</span><br/><br/>
5923 5924 5925 5926

        <b>In general you should leave this option alone, unless you
        are very certain you know what you are doing.</b>
      </dd>
5927 5928 5929 5930 5931 5932 5933
      <dt><code>tx_queue_size</code></dt>
      <dd>
        The optional <code>tx_queue_size</code> attribute controls
        the size of virtio ring for each queue as described above.
        The default value is hypervisor dependent and may change
        across its releases. Moreover, some hypervisors may pose
        some restrictions on actual value. For instance, QEMU
5934 5935 5936 5937
        v2.9  requires value to be a power of two from [256, 1024]
        range. In addition to that, this may work only for a subset of
        interface types, e.g. aforementioned QEMU enables this option
        only for <code>vhostuser</code> type.
5938
        <span class="since">Since 3.7.0 (QEMU and KVM only)</span><br/><br/>
5939 5940 5941 5942

        <b>In general you should leave this option alone, unless you
        are very certain you know what you are doing.</b>
      </dd>
5943 5944 5945 5946 5947 5948
      <dt>virtio options</dt>
      <dd>
        For virtio interfaces,
        <a href="#elementsVirtio">Virtio-specific options</a> can also be
        set. (<span class="since">Since 3.5.0</span>)
      </dd>
5949 5950 5951 5952 5953 5954 5955
    </dl>
    <p>
      Offloading options for the host and guest can be configured using
      the following sub-elements:
    </p>
    <dl>
      <dt><code>host</code></dt>
5956 5957 5958 5959 5960 5961 5962
      <dd>
        The <code>csum</code>, <code>gso</code>, <code>tso4</code>,
        <code>tso6</code>, <code>ecn</code> and <code>ufo</code>
        attributes with possible values <code>on</code>
        and <code>off</code> can be used to turn off host offloading options.
        By default, the supported offloads are enabled by QEMU.
        <span class="since">Since 1.2.9 (QEMU only)</span>
5963 5964 5965 5966
        The <code>mrg_rxbuf</code> attribute can be used to control
        mergeable rx buffers on the host side. Possible values are
        <code>on</code> (default) and <code>off</code>.
        <span class="since">Since 1.2.13 (QEMU only)</span>
5967
      </dd>
5968
      <dt><code>guest</code></dt>
5969 5970 5971 5972 5973 5974 5975 5976
      <dd>
        The <code>csum</code>, <code>tso4</code>,
        <code>tso6</code>, <code>ecn</code> and <code>ufo</code>
        attributes with possible values <code>on</code>
        and <code>off</code> can be used to turn off guest offloading options.
        By default, the supported offloads are enabled by QEMU.
        <span class="since">Since 1.2.9 (QEMU only)</span>
      </dd>
5977 5978
    </dl>

5979
    <h5><a id="elementsBackendOptions">Setting network backend-specific options</a></h5>
5980 5981

<pre>
5982 5983 5984 5985 5986 5987 5988 5989
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet1'/&gt;
    &lt;model type='virtio'/&gt;
    <b>&lt;backend tap='/dev/net/tun' vhost='/dev/vhost-net'/&gt;</b>
    &lt;driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5'/&gt;
M
Michal Privoznik 已提交
5990 5991 5992
    <b>&lt;tune&gt;
      &lt;sndbuf&gt;1600&lt;/sndbuf&gt;
    &lt;/tune&gt;</b>
5993 5994 5995
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5996 5997 5998

    <p>
      For tuning the backend of the network, the <code>backend</code> element
5999 6000
      can be used. The <code>vhost</code> attribute can override the default vhost
      device path (<code>/dev/vhost-net</code>) for devices with <code>virtio</code> model.
6001 6002
      The <code>tap</code> attribute overrides the tun/tap device path (default:
      <code>/dev/net/tun</code>) for network and bridge interfaces. This does not work
M
Michal Privoznik 已提交
6003 6004 6005 6006 6007 6008
      in session mode. <span class="since">Since 1.2.9</span>
    </p>
    <p>
      For tap devices there is also <code>sndbuf</code> element which can
      adjust the size of send buffer in the host. <span class="since">Since
      0.8.8</span>
6009
    </p>
6010
    <h5><a id="elementsNICSTargetOverride">Overriding the target element</a></h5>
6011

6012
<pre>
6013 6014 6015 6016 6017 6018 6019 6020
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    <b>&lt;target dev='vnet1'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6021 6022

    <p>
E
Eric Blake 已提交
6023 6024
      If no target is specified, certain hypervisors will
      automatically generate a name for the created tun device. This
6025
      name can be manually specified, however the name <i>should not
6026 6027 6028
      start with either 'vnet', 'vif', 'macvtap', or 'macvlan'</i>,
      which are prefixes reserved by libvirt and certain hypervisors.
      Manually specified targets using these prefixes may be ignored.
6029 6030
    </p>

6031 6032 6033 6034 6035 6036 6037 6038
    <p>
      Note that for LXC containers, this defines the name of the interface
      on the host side. <span class="since">Since 1.2.7</span>, to define
      the name of the device on the guest side, the <code>guest</code>
      element should be used, as in the following snippet:
    </p>

<pre>
6039 6040 6041 6042 6043 6044 6045 6046
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    <b>&lt;guest dev='myeth'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6047

6048
    <h5><a id="elementsNICSBoot">Specifying boot order</a></h5>
6049 6050

<pre>
6051 6052 6053 6054 6055 6056 6057 6058 6059
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet1'/&gt;
    <b>&lt;boot order='1'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6060 6061

    <p>
6062
      For hypervisors which support this, you can set a specific NIC to
6063 6064 6065 6066 6067 6068 6069 6070
      be used for network boot. The <code>order</code> attribute determines
      the order in which devices will be tried during boot sequence. The
      per-device <code>boot</code> elements cannot be used together with
      general boot elements in
      <a href="#elementsOSBIOS">BIOS bootloader</a> section.
      <span class="since">Since 0.8.8</span>
    </p>

6071
    <h5><a id="elementsNICSROM">Interface ROM BIOS configuration</a></h5>
6072 6073

<pre>
6074 6075 6076 6077 6078 6079 6080 6081 6082
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet1'/&gt;
    <b>&lt;rom bar='on' file='/etc/fake/boot.bin'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6083 6084 6085 6086 6087 6088 6089 6090 6091 6092

    <p>
      For hypervisors which support this, you can change how a PCI Network
      device's ROM is presented to the guest. The <code>bar</code>
      attribute can be set to "on" or "off", and determines whether
      or not the device's ROM will be visible in the guest's memory
      map. (In PCI documentation, the "rombar" setting controls the
      presence of the Base Address Register for the ROM). If no rom
      bar is specified, the qemu default will be used (older
      versions of qemu used a default of "off", while newer qemus
6093 6094 6095 6096 6097 6098
      have a default of "on").
      The optional <code>file</code> attribute is used to point to a
      binary file to be presented to the guest as the device's ROM
      BIOS. This can be useful to provide an alternative boot ROM for a
      network device.
      <span class="since">Since 0.9.10 (QEMU and KVM only)</span>.
6099
    </p>
6100
    <h5><a id="elementDomain">Setting up a network backend in a driver domain</a></h5>
6101
<pre>
6102 6103
...
&lt;devices&gt;
6104
  ...
6105 6106 6107 6108 6109 6110 6111
  &lt;interface type='bridge'&gt;
    &lt;source bridge='br0'/&gt;
    <b>&lt;backenddomain name='netvm'/&gt;</b>
  &lt;/interface&gt;
  ...
&lt;/devices&gt;
...</pre>
6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122

    <p>
      The optional <code>backenddomain</code> element allows specifying a
      backend domain (aka driver domain) for the interface. Use the
      <code>name</code> attribute to specify the backend domain name. You
      can use it to create a direct network link between domains (so data
      will not go through host system). Use with type 'ethernet' to create
      plain network link, or with type 'bridge' to connect to a bridge inside
      the backend domain.
      <span class="since">Since 1.2.13 (Xen only)</span>
    </p>
6123

6124
    <h5><a id="elementQoS">Quality of service</a></h5>
6125 6126

<pre>
6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet0'/&gt;
    <b>&lt;bandwidth&gt;
      &lt;inbound average='1000' peak='5000' floor='200' burst='1024'/&gt;
      &lt;outbound average='128' peak='256' burst='256'/&gt;
    &lt;/bandwidth&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6139 6140 6141

    <p>
      This part of interface XML provides setting quality of service. Incoming
J
John Ferlan 已提交
6142 6143 6144 6145
      and outgoing traffic can be shaped independently.
      The <code>bandwidth</code> element and its child elements are described
      in the <a href="formatnetwork.html#elementQoS">QoS</a> section of
      the Network XML.
6146 6147
    </p>

6148
    <h5><a id="elementVlanTag">Setting VLAN tag (on supported network types only)</a></h5>
6149 6150

<pre>
6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164 6165 6166 6167 6168 6169 6170
...
&lt;devices&gt;
  &lt;interface type='bridge'&gt;
    <b>&lt;vlan&gt;</b>
      <b>&lt;tag id='42'/&gt;</b>
    <b>&lt;/vlan&gt;</b>
    &lt;source bridge='ovsbr0'/&gt;
    &lt;virtualport type='openvswitch'&gt;
      &lt;parameters interfaceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/&gt;
    &lt;/virtualport&gt;
  &lt;/interface&gt;
  &lt;interface type='bridge'&gt;
    <b>&lt;vlan trunk='yes'&gt;</b>
      <b>&lt;tag id='42'/&gt;</b>
      <b>&lt;tag id='123' nativeMode='untagged'/&gt;</b>
    <b>&lt;/vlan&gt;</b>
    ...
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6171 6172 6173

    <p>
      If (and only if) the network connection used by the guest
6174
      supports VLAN tagging transparent to the guest, an
6175
      optional <code>&lt;vlan&gt;</code> element can specify one or
6176 6177 6178 6179 6180 6181 6182 6183 6184
      more VLAN tags to apply to the guest's network
      traffic <span class="since">Since 0.10.0</span>. Network
      connections that support guest-transparent VLAN tagging include
      1) type='bridge' interfaces connected to an Open vSwitch bridge
      <span class="since">Since 0.10.0</span>, 2) SRIOV Virtual
      Functions (VF) used via type='hostdev' (direct device
      assignment) <span class="since">Since 0.10.0</span>, and 3)
      SRIOV VFs used via type='direct' with mode='passthrough'
      (macvtap "passthru" mode) <span class="since">Since
6185
      1.3.5</span>. All other connection types, including standard
6186 6187 6188
      linux bridges and libvirt's own virtual networks, <b>do not</b>
      support it. 802.1Qbh (vn-link) and 802.1Qbg (VEPA) switches
      provide their own way (outside of libvirt) to tag guest traffic
6189 6190 6191 6192 6193 6194 6195 6196 6197
      onto a specific VLAN. Each tag is given in a
      separate <code>&lt;tag&gt;</code> subelement
      of <code>&lt;vlan&gt;</code> (for example: <code>&lt;tag
      id='42'/&gt;</code>). For VLAN trunking of multiple tags (which
      is supported only on Open vSwitch connections),
      multiple <code>&lt;tag&gt;</code> subelements can be specified,
      which implies that the user wants to do VLAN trunking on the
      interface for all the specified tags. In the case that VLAN
      trunking of a single tag is desired, the optional
6198
      attribute <code>trunk='yes'</code> can be added to the toplevel
6199 6200
      <code>&lt;vlan&gt;</code> element to differentiate trunking of a
      single tag from normal tagging.
6201
    </p>
6202
    <p>
6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213
      For network connections using Open vSwitch it is also possible
      to configure 'native-tagged' and 'native-untagged' VLAN modes
      <span class="since">Since 1.1.0.</span> This is done with the
      optional <code>nativeMode</code> attribute on
      the <code>&lt;tag&gt;</code> subelement: <code>nativeMode</code>
      may be set to 'tagged' or 'untagged'. The <code>id</code>
      attribute of the <code>&lt;tag&gt;</code> subelement
      containing <code>nativeMode</code> sets which VLAN is considered
      to be the "native" VLAN for this interface, and
      the <code>nativeMode</code> attribute determines whether or not
      traffic for that VLAN will be tagged.
6214 6215
    </p>

6216
    <h5><a id="elementLink">Modifying virtual link state</a></h5>
6217
<pre>
6218 6219 6220 6221 6222 6223 6224 6225 6226
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet0'/&gt;
    <b>&lt;link state='down'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6227 6228 6229 6230 6231 6232 6233 6234 6235 6236

    <p>
      This element provides means of setting state of the virtual network link.
      Possible values for attribute <code>state</code> are <code>up</code> and
      <code>down</code>. If <code>down</code> is specified as the value, the interface
      behaves as if it had the network cable disconnected. Default behavior if this
      element is unspecified is to have the link state <code>up</code>.
      <span class="since">Since 0.9.5</span>
    </p>

6237
    <h5><a id="mtu">MTU configuration</a></h5>
6238 6239 6240 6241 6242 6243 6244 6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255
<pre>
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet0'/&gt;
    <b>&lt;mtu size='1500'/&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>

    <p>
      This element provides means of setting MTU of the virtual network link.
      Currently there is just one attribute <code>size</code> which accepts a
      non-negative integer which specifies the MTU size for the interface.
      <span class="since">Since 3.1.0</span>
    </p>

6256
    <h5><a id="coalesce">Coalesce settings</a></h5>
6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275
<pre>
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet0'/&gt;
    <b>&lt;coalesce&gt;
      &lt;rx&gt;
        &lt;frames max='7'/&gt;
      &lt;/rx&gt;
    &lt;/coalesce&gt;</b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>

    <p>
      This element provides means of setting coalesce settings for
      some interface devices (currently only type <code>network</code>
      and <code>bridge</code>.  Currently there is just one attribute,
6276
      <code>max</code>, to tweak, in element <code>frames</code> for
6277 6278 6279 6280 6281 6282
      the <code>rx</code> group, which accepts a non-negative integer
      that specifies the maximum number of packets that will be
      received before an interrupt.
      <span class="since">Since 3.3.0</span>
    </p>

6283
    <h5><a id="ipconfig">IP configuration</a></h5>
6284
<pre>
6285 6286 6287 6288 6289 6290 6291 6292 6293 6294
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
    &lt;target dev='vnet0'/&gt;
    <b>&lt;ip address='192.168.122.5' prefix='24'/&gt;</b>
    <b>&lt;ip address='192.168.122.5' prefix='24' peer='10.0.0.10'/&gt;</b>
    <b>&lt;route family='ipv4' address='192.168.122.0' prefix='24' gateway='192.168.122.1'/&gt;</b>
    <b>&lt;route family='ipv4' address='192.168.122.8' gateway='192.168.122.1'/&gt;</b>
  &lt;/interface&gt;
6295
  ...
6296 6297 6298 6299 6300 6301 6302 6303
  &lt;hostdev mode='capabilities' type='net'&gt;
    &lt;source&gt;
      &lt;interface&gt;eth0&lt;/interface&gt;
    &lt;/source&gt;
    <b>&lt;ip address='192.168.122.6' prefix='24'/&gt;</b>
    <b>&lt;route family='ipv4' address='192.168.122.0' prefix='24' gateway='192.168.122.1'/&gt;</b>
    <b>&lt;route family='ipv4' address='192.168.122.8' gateway='192.168.122.1'/&gt;</b>
  &lt;/hostdev&gt;
6304
  ...
6305 6306
&lt;/devices&gt;
...
6307 6308 6309
</pre>

    <p>
6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324
      <span class="since">Since 1.2.12</span> network devices and
      hostdev devices with network capabilities can optionally be provided
      one or more IP addresses to set on the network device in the
      guest. Note that some hypervisors or network device types will
      simply ignore them or only use the first one.
      The <code>family</code> attribute can be set to
      either <code>ipv4</code> or <code>ipv6</code>, and the
      <code>address</code> attribute contains the IP address. The
      optional <code>prefix</code> is the number of 1 bits in the
      netmask, and will be automatically set if not specified - for
      IPv4 the default prefix is determined according to the network
      "class" (A, B, or C - see RFC870), and for IPv6 the default
      prefix is 64. The optional <code>peer</code> attribute holds the
      IP address of the other end of a point-to-point network
      device <span class="since">(since 2.1.0)</span>.
6325 6326
    </p>

6327
    <p>
6328 6329 6330 6331 6332 6333
    <span class="since">Since 1.2.12</span> route elements can also be
    added to define IP routes to add in the guest.  The attributes of
    this element are described in the documentation for
    the <code>route</code> element
    in <a href="formatnetwork.html#elementsStaticroute">network
    definitions</a>.  This is used by the LXC driver.
6334 6335
    </p>

6336
<pre>
6337 6338 6339 6340 6341 6342 6343 6344
...
&lt;devices&gt;
  &lt;interface type='ethernet'&gt;
    <b>&lt;source/&gt;</b>
      <b>&lt;ip address='192.168.123.1' prefix='24'/&gt;</b>
      <b>&lt;ip address='10.0.0.10' prefix='24' peer='192.168.122.5'/&gt;</b>
      <b>&lt;route family='ipv4' address='192.168.42.0' prefix='24' gateway='192.168.123.4'/&gt;</b>
    <b>&lt;source/&gt;</b>
6345
    ...
6346
  &lt;/interface&gt;
6347
  ...
6348 6349
&lt;/devices&gt;
...
6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361
</pre>

    <p>
      <span class="since">Since 2.1.0</span> network devices of type
      "ethernet" can optionally be provided one or more IP addresses
      and one or more routes to set on the <b>host</b> side of the
      network device. These are configured as subelements of
      the <code>&lt;source&gt;</code> element of the interface, and
      have the same attributes as the similarly named elements used to
      configure the guest side of the interface (described above).
    </p>

6362
    <h5><a id="elementVhostuser">vhost-user interface</a></h5>
M
Michele Paolino 已提交
6363 6364 6365 6366 6367 6368 6369 6370 6371

    <p>
    <span class="since">Since 1.2.7</span> the vhost-user enables the
    communication between a QEMU virtual machine and other userspace process
    using the Virtio transport protocol.  A char dev (e.g. Unix socket) is used
    for the control plane, while the data plane is based on shared memory.
    </p>

<pre>
6372 6373 6374 6375 6376 6377 6378 6379 6380
...
&lt;devices&gt;
  &lt;interface type='vhostuser'&gt;
    &lt;mac address='52:54:00:3b:83:1a'/&gt;
    &lt;source type='unix' path='/tmp/vhost1.sock' mode='server'/&gt;
    &lt;model type='virtio'/&gt;
  &lt;/interface&gt;
  &lt;interface type='vhostuser'&gt;
    &lt;mac address='52:54:00:3b:83:1b'/&gt;
6381 6382 6383
    &lt;source type='unix' path='/tmp/vhost2.sock' mode='client'&gt;
      &lt;reconnect enabled='yes' timeout='10'/&gt;
    &lt;/source&gt;
6384 6385 6386 6387 6388
    &lt;model type='virtio'/&gt;
    &lt;driver queues='5'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
M
Michele Paolino 已提交
6389 6390 6391 6392 6393 6394 6395 6396 6397 6398

    <p>
      The <code>&lt;source&gt;</code> element has to be specified
      along with the type of char device.
      Currently, only type='unix' is supported, where the path (the
      directory path of the socket) and mode attributes are required.
      Both <code>mode='server'</code> and <code>mode='client'</code>
      are supported.
      vhost-user requires the virtio model type, thus the
      <code>&lt;model&gt;</code> element is mandatory.
6399 6400 6401 6402 6403 6404 6405
      <span class="since">Since 4.1.0</span> the element has an
      optional child element <code>reconnect</code> which
      configures reconnect timeout if the connection is lost. It
      has two attributes <code>enabled</code> (which accepts
      <code>yes</code> and <code>no</code>) and
      <code>timeout</code> which specifies the amount of seconds
      after which hypervisor tries to reconnect.
M
Michele Paolino 已提交
6406 6407
    </p>

6408
    <h5><a id="elementNwfilter">Traffic filtering with NWFilter</a></h5>
6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419

    <p>
    <span class="since">Since 0.8.0</span> an <code>nwfilter</code> profile
    can be assigned to a domain interface, which allows configuring
    traffic filter rules for the virtual machine.

    See the <a href="formatnwfilter.html">nwfilter</a> documentation for more
    complete details.
    </p>

<pre>
6420 6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431
...
&lt;devices&gt;
  &lt;interface ...&gt;
    ...
    &lt;filterref filter='clean-traffic'/&gt;
  &lt;/interface&gt;
  &lt;interface ...&gt;
    ...
    &lt;filterref filter='myfilter'&gt;
      &lt;parameter name='IP' value='104.207.129.11'/&gt;
      &lt;parameter name='IP6_ADDR' value='2001:19f0:300:2102::'/&gt;
      &lt;parameter name='IP6_MASK' value='64'/&gt;
6432
      ...
6433 6434 6435 6436
    &lt;/filterref&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447

    <p>
      The <code>filter</code> attribute specifies the name of the nwfilter
      to use. Optional <code>&lt;parameter&gt;</code> elements may be
      specified for passing additional info to the nwfilter via the
      <code>name</code> and <code>value</code> attributes. See
      the <a href="formatnwfilter.html#nwfconceptsvars">nwfilter</a>
      docs for info on parameters.
    </p>


6448
    <h4><a id="elementsInput">Input devices</a></h4>
D
Daniel P. Berrange 已提交
6449 6450

    <p>
E
Eric Blake 已提交
6451 6452 6453 6454
      Input devices allow interaction with the graphical framebuffer
      in the guest virtual machine. When enabling the framebuffer, an
      input device is automatically provided. It may be possible to
      add additional devices explicitly, for example,
D
Daniel P. Berrange 已提交
6455 6456 6457
      to provide a graphics tablet for absolute cursor movement.
    </p>

6458
<pre>
6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470
...
&lt;devices&gt;
  &lt;input type='mouse' bus='usb'/&gt;
  &lt;input type='keyboard' bus='usb'/&gt;
  &lt;input type='mouse' bus='virtio'/&gt;
  &lt;input type='keyboard' bus='virtio'/&gt;
  &lt;input type='tablet' bus='virtio'/&gt;
  &lt;input type='passthrough' bus='virtio'&gt;
    &lt;source evdev='/dev/input/event1/&gt;
  &lt;/input&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
6471 6472 6473

    <dl>
      <dt><code>input</code></dt>
E
Eric Blake 已提交
6474
      <dd>The <code>input</code> element has one mandatory attribute,
6475 6476 6477
        the <code>type</code> whose value can be 'mouse', 'tablet',
        (<span class="since">since 1.2.2</span>) 'keyboard' or
        (<span class="since">since 1.3.0</span>) 'passthrough'.
6478 6479
        The tablet provides absolute cursor movement,
        while the mouse uses relative movement. The optional
M
Matthew Booth 已提交
6480
        <code>bus</code> attribute can be used to refine the exact device type.
6481 6482
        It takes values "xen" (paravirtualized), "ps2" and "usb" or
        (<span class="since">since 1.3.0</span>) "virtio".</dd>
D
Daniel P. Berrange 已提交
6483 6484
    </dl>

E
Eric Blake 已提交
6485 6486 6487
    <p>
      The <code>input</code> element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
6488 6489
      device to a particular PCI
      slot, <a href="#elementsAddress">documented above</a>.
6490 6491
      On S390, <code>address</code> can be used to provide a CCW address for
      an input device (<span class="since">since 4.2.0</span>).
6492 6493 6494 6495

      For type <code>passthrough</code>, the mandatory sub-element <code>source</code>
      must have an <code>evdev</code> attribute containing the absolute path to the
      event device passed through to guests. (KVM only)
6496 6497 6498 6499 6500 6501

      <span class="since">Since 5.2.0</span>, the <code>input</code> element
      accepts a <code>model</code> attribute which has the values 'virtio',
      'virtio-transitional' and 'virtio-non-transitional'. See
      <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
      for more details.
E
Eric Blake 已提交
6502
    </p>
D
Daniel P. Berrange 已提交
6503

6504 6505 6506 6507 6508 6509 6510
    <p>
        The subelement <code>driver</code> can be used to tune the virtio
        options of the device:
        <a href="#elementsVirtio">Virtio-specific options</a> can also be
        set. (<span class="since">Since 3.5.0</span>)
    </p>

6511
    <h4><a id="elementsHub">Hub devices</a></h4>
M
Marc-André Lureau 已提交
6512 6513 6514 6515 6516 6517 6518 6519

    <p>
      A hub is a device that expands a single port into several so
      that there are more ports available to connect devices to a host
      system.
    </p>

<pre>
6520 6521 6522 6523 6524
...
&lt;devices&gt;
  &lt;hub type='usb'/&gt;
&lt;/devices&gt;
...</pre>
M
Marc-André Lureau 已提交
6525 6526 6527 6528 6529 6530 6531 6532 6533

    <dl>
      <dt><code>hub</code></dt>
      <dd>The <code>hub</code> element has one mandatory attribute,
        the <code>type</code> whose value can only be 'usb'.</dd>
    </dl>

    <p>
      The <code>hub</code> element has an optional
6534 6535 6536 6537
      sub-element <code>&lt;address&gt;</code>
      with <code>type='usb'</code>which can tie the device to a
      particular controller, <a href="#elementsAddress">documented
      above</a>.
M
Marc-André Lureau 已提交
6538 6539
    </p>

6540
    <h4><a id="elementsGraphics">Graphical framebuffers</a></h4>
D
Daniel P. Berrange 已提交
6541 6542 6543 6544 6545 6546 6547 6548

    <p>
      A graphics device allows for graphical interaction with the
      guest OS. A guest will typically have either a framebuffer
      or a text console configured to allow interaction with the
      admin.
    </p>

6549
<pre>
6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562
...
&lt;devices&gt;
  &lt;graphics type='sdl' display=':0.0'/&gt;
  &lt;graphics type='vnc' port='5904' sharePolicy='allow-exclusive'&gt;
    &lt;listen type='address' address='1.2.3.4'/&gt;
  &lt;/graphics&gt;
  &lt;graphics type='rdp' autoport='yes' multiUser='yes' /&gt;
  &lt;graphics type='desktop' fullscreen='yes'/&gt;
  &lt;graphics type='spice'&gt;
    &lt;listen type='network' network='rednet'/&gt;
  &lt;/graphics&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
6563 6564 6565

    <dl>
      <dt><code>graphics</code></dt>
6566 6567 6568 6569
      <dd>
        <p>
          The <code>graphics</code> element has a mandatory <code>type</code>
          attribute which takes the value <code>sdl</code>, <code>vnc</code>,
6570 6571
          <code>spice</code>, <code>rdp</code>, <code>desktop</code> or
          <code>egl-headless</code>:
6572
        </p>
6573
        <dl>
6574
          <dt><code>sdl</code></dt>
6575
          <dd>
6576 6577 6578 6579 6580 6581 6582
            <p>
              This displays a window on the host desktop, it can take 3 optional
              arguments: a <code>display</code> attribute for the display to use,
              an <code>xauth</code> attribute for the authentication identifier,
              and an optional <code>fullscreen</code> attribute accepting values
              <code>yes</code> or <code>no</code>.
            </p>
6583 6584 6585 6586 6587 6588

            <p>
              You can use a <code>gl</code> with the <code>enable="yes"</code>
              property to enable OpenGL support in SDL. Likewise you can
              explicitly disable OpenGL support with <code>enable="no"</code>.
            </p>
6589
          </dd>
6590
          <dt><code>vnc</code></dt>
6591
          <dd>
6592 6593 6594 6595 6596
            <p>
              Starts a VNC server. The <code>port</code> attribute specifies
              the TCP port number (with -1 as legacy syntax indicating that it
              should be auto-allocated). The <code>autoport</code> attribute is
              the new preferred syntax for indicating auto-allocation of the TCP
6597
              port to use. The <code>passwd</code> attribute provides a VNC
6598 6599 6600 6601
              password in clear text. If the <code>passwd</code> attribute is
              set to an empty string, then VNC access is disabled. The
              <code>keymap</code> attribute specifies the keymap to use. It is
              possible to set a limit on the validity of the password by giving
V
Ville Skyttä 已提交
6602
              a timestamp <code>passwdValidTo='2010-04-09T15:51:00'</code>
6603 6604
              assumed to be in UTC. The <code>connected</code> attribute allows
              control of connected client during password changes. VNC accepts
6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622 6623 6624 6625 6626 6627 6628 6629
              <code>keep</code> value only <span class="since">since 0.9.3</span>.
              NB, this may not be supported by all hypervisors.
            </p>
            <p>
              The optional <code>sharePolicy</code> attribute specifies vnc
              server display sharing policy. <code>allow-exclusive</code> allows
              clients to ask for exclusive access by dropping other connections.
              Connecting multiple clients in parallel requires all clients asking
              for a shared session (vncviewer: -Shared switch). This is
              the default value. <code>force-shared</code> disables exclusive
              client access, every connection has to specify -Shared switch for
              vncviewer. <code>ignore</code> welcomes every connection
              unconditionally <span class="since">since 1.0.6</span>.
            </p>
            <p>
              Rather than using listen/port, QEMU supports a <code>socket</code>
              attribute for listening on a unix domain socket path
              <span class="since">Since 0.8.8</span>.
            </p>
            <p>
              For VNC WebSocket functionality, <code>websocket</code> attribute
              may be used to specify port to listen on (with -1 meaning
              auto-allocation and <code>autoport</code> having no effect due to
              security reasons) <span class="since">Since 1.0.6</span>.
            </p>
6630 6631 6632 6633 6634
            <p>
              Although VNC doesn't support OpenGL natively, it can be paired
              with graphics type <code>egl-headless</code> (see below) which
              will instruct QEMU to open and use drm nodes for OpenGL rendering.
            </p>
6635
          </dd>
6636
          <dt><code>spice</code> <span class="since">Since 0.8.6</span></dt>
6637
          <dd>
E
Eric Blake 已提交
6638
            <p>
6639 6640 6641 6642 6643
              Starts a SPICE server. The <code>port</code> attribute specifies
              the TCP port number (with -1 as legacy syntax indicating that it
              should be auto-allocated), while <code>tlsPort</code> gives
              an alternative secure port number. The <code>autoport</code>
              attribute is the new preferred syntax for indicating
6644
              auto-allocation of needed port numbers. The <code>passwd</code>
6645 6646 6647 6648
              attribute provides a SPICE password in clear text. If the
              <code>passwd</code> attribute is set to an empty string, then
              SPICE access is disabled. The <code>keymap</code> attribute
              specifies the keymap to use. It is possible to set a limit on
V
Ville Skyttä 已提交
6649
              the validity of the password by giving a timestamp
6650 6651
              <code>passwdValidTo='2010-04-09T15:51:00'</code> assumed to be
              in UTC.
6652 6653 6654 6655 6656 6657 6658
            </p>
            <p>
              The <code>connected</code> attribute allows control of connected
              client during password changes. SPICE accepts <code>keep</code> to
              keep client connected, <code>disconnect</code> to disconnect client
              and <code>fail</code> to fail changing password . NB, this may not
              be supported by all hypervisors.
6659
              <span class="since">Since 0.9.3</span>
6660 6661
            </p>
            <p>
6662 6663
              The <code>defaultMode</code> attribute sets the default channel
              security policy, valid values are <code>secure</code>,
6664 6665 6666 6667
              <code>insecure</code> and the default <code>any</code> (which is
              secure if possible, but falls back to insecure rather than erroring
              out if no secure path is available).
              <span class="since">Since 0.9.12</span>
E
Eric Blake 已提交
6668 6669
            </p>
            <p>
6670 6671 6672 6673 6674 6675 6676 6677
              When SPICE has both a normal and TLS secured TCP port configured,
              it can be desirable to restrict what channels can be run on each
              port. This is achieved by adding one or more <code>&lt;channel&gt;
              </code> elements inside the main <code>&lt;graphics&gt;</code>
              element and setting the <code>mode</code> attribute to either
              <code>secure</code> or <code>insecure</code>. Setting the mode
              attribute overrides the default value as set by
              the <code>defaultMode</code> attribute. (Note that specifying
6678
              <code>any</code> as mode discards the entry as the channel would
6679 6680 6681
              inherit the default mode anyways.) Valid channel names include
              <code>main</code>, <code>display</code>, <code>inputs</code>,
              <code>cursor</code>, <code>playback</code>, <code>record</code>
6682
              (all <span class="since"> since 0.8.6</span>);
6683 6684
              <code>smartcard</code> (<span class="since">since 0.8.8</span>);
              and <code>usbredir</code> (<span class="since">since 0.9.12</span>).
E
Eric Blake 已提交
6685 6686
            </p>
            <pre>
6687 6688 6689 6690 6691 6692 6693 6694
&lt;graphics type='spice' port='-1' tlsPort='-1' autoport='yes'&gt;
  &lt;channel name='main' mode='secure'/&gt;
  &lt;channel name='record' mode='insecure'/&gt;
  &lt;image compression='auto_glz'/&gt;
  &lt;streaming mode='filter'/&gt;
  &lt;clipboard copypaste='no'/&gt;
  &lt;mouse mode='client'/&gt;
  &lt;filetransfer enable='no'/&gt;
6695
  &lt;gl enable='yes' rendernode='/dev/dri/by-path/pci-0000:00:02.0-render'/&gt;
6696
&lt;/graphics&gt;</pre>
6697
            <p>
6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709
              Spice supports variable compression settings for audio, images and
              streaming. These settings are accessible via the <code>compression
              </code> attribute in all following elements: <code>image</code> to
              set image compression (accepts <code>auto_glz</code>,
              <code>auto_lz</code>, <code>quic</code>, <code>glz</code>,
              <code>lz</code>, <code>off</code>), <code>jpeg</code> for JPEG
              compression for images over wan (accepts <code>auto</code>,
              <code>never</code>, <code>always</code>), <code>zlib</code> for
              configuring wan image compression (accepts <code>auto</code>,
              <code>never</code>, <code>always</code>)  and <code>playback</code>
              for enabling audio stream compression (accepts <code>on</code> or
              <code>off</code>). <span class="since">Since 0.9.1</span>
6710
            </p>
6711
            <p>
6712 6713 6714 6715
              Streaming mode is set by the <code>streaming</code> element,
              settings its <code>mode</code> attribute to one of
              <code>filter</code>, <code>all</code> or <code>off</code>.
              <span class="since">Since 0.9.2</span>
6716
            </p>
6717
            <p>
6718 6719 6720 6721
              Copy &amp; Paste functionality (via Spice agent) is set by the
              <code>clipboard</code> element. It is enabled by default, and can
              be disabled by setting the <code>copypaste</code> property to
              <code>no</code>. <span class="since">Since 0.9.3</span>
6722
            </p>
P
Peng Zhou 已提交
6723
            <p>
6724 6725 6726 6727
              Mouse mode is set by the <code>mouse</code> element, setting its
              <code>mode</code> attribute to one of <code>server</code> or
              <code>client</code>. If no mode is specified, the qemu default will
              be used (client mode). <span class="since">Since 0.9.11</span>
P
Peng Zhou 已提交
6728
            </p>
6729 6730
            <p>
              File transfer functionality (via Spice agent) is set using the
6731 6732 6733
              <code>filetransfer</code> element. It is enabled by default, and
              can be disabled by setting the <code>enable</code> property to
              <code>no</code>. <span class="since">Since 1.2.2</span>
6734
            </p>
6735
            <p>
6736 6737 6738
              Spice may provide accelerated server-side rendering with OpenGL.
              You can enable or disable OpenGL support explicitly with
              the <code>gl</code> element, by setting the <code>enable</code>
6739
              property. (QEMU only, <span class="since">since 1.3.3</span>).
6740 6741 6742 6743 6744 6745
              Note that this only works locally, since this requires usage of
              UNIX sockets, i.e. using <code>listen</code> types 'socket' or
              'none'. For accelerated OpenGL with remote support, consider
              pairing this element with type <code>egl-headless</code>
              (see below). However, this will deliver weaker performance
              compared to native Spice OpenGL support.
6746
            </p>
6747 6748 6749 6750 6751
            <p>
              By default, QEMU will pick the first available GPU DRM render node.
              You may specify a DRM render node path to use instead. (QEMU only,
              <span class="since">since 3.1.0</span>).
            </p>
6752
          </dd>
6753
          <dt><code>rdp</code></dt>
6754
          <dd>
6755 6756 6757 6758 6759
            <p>
              Starts a RDP server. The <code>port</code> attribute specifies the
              TCP port number (with -1 as legacy syntax indicating that it should
              be auto-allocated). The <code>autoport</code> attribute is the new
              preferred syntax for indicating auto-allocation of the TCP port to
6760 6761 6762 6763
              use. In the VirtualBox driver, the <code>autoport</code> will make
              the hypervisor pick available port from 3389-3689 range when the VM
              is started. The chosen port will be reflected in the <code>port</code>
              attribute. The <code>multiUser</code> attribute is a boolean deciding
6764
              whether multiple simultaneous connections to the VM are permitted.
6765
              The <code>replaceUser</code> attribute is a boolean deciding whether
6766 6767 6768 6769
              the existing connection must be dropped and a new connection must
              be established by the VRDP server, when a new client connects in
              single connection mode.
            </p>
6770
          </dd>
6771
          <dt><code>desktop</code></dt>
6772
          <dd>
6773 6774 6775 6776 6777 6778 6779
            <p>
              This value is reserved for VirtualBox domains for the moment. It
              displays a window on the host desktop, similarly to "sdl", but
              using the VirtualBox viewer. Just like "sdl", it accepts
              the optional attributes <code>display</code> and
              <code>fullscreen</code>.
            </p>
6780
          </dd>
6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791
          <dt><code>egl-headless</code><span class="since">Since 4.6.0</span></dt>
          <dd>
            <p>
              This display type provides support for an OpenGL accelerated
              display accessible both locally and remotely (for comparison,
              Spice's native OpenGL support only works locally using UNIX
              sockets at the moment, but has better performance). Since this
              display type doesn't provide any window or graphical console like
              the other types, for practical reasons it should be paired with
              either <code>vnc</code> or <code>spice</code> graphics types.
              This display type is only supported by QEMU domains
6792 6793 6794 6795 6796
              (needs QEMU <span class="since">2.10</span> or newer).
              <span class="Since">5.0.0</span> this element accepts a
              <code>&lt;gl/&gt;</code> sub-element with an optional attribute
              <code>rendernode</code> which can be used to specify an absolute
              path to a host's DRI device to be used for OpenGL rendering.
6797 6798 6799
            </p>
            <pre>
&lt;graphics type='spice' autoport='yes'/&gt;
6800 6801 6802
&lt;graphics type='egl-headless'&gt;
  &lt;gl rendernode='/dev/dri/renderD128'/&gt;
&lt;/graphics&gt;
6803 6804
            </pre>
          </dd>
6805 6806 6807 6808
        </dl>
      </dd>
    </dl>

6809
    <p>
6810 6811 6812 6813 6814 6815
      Graphics device uses a <code>&lt;listen&gt;</code> to set up where
      the device should listen for clients. It has a mandatory attribute
      <code>type</code> which specifies the listen type. Only <code>vnc</code>,
      <code>spice</code> and <code>rdp</code> supports <code>&lt;listen&gt;
      </code> element. <span class="since">Since 0.9.4</span>.
      Available types are:
6816 6817 6818
    </p>
    <dl>
      <dt><code>address</code></dt>
6819 6820 6821 6822 6823 6824 6825
      <dd>
        <p>
          Tells a graphics device to use an address specified in the
          <code>address</code> attribute, which will contain either an IP address
          or hostname (which will be resolved to an IP address via a DNS query)
          to listen on.
        </p>
6826 6827 6828 6829 6830 6831 6832 6833 6834
        <p>
          It is possible to omit the <code>address</code> attribute in order to
          use an address from config files <span class="since">Since 1.3.5</span>.
        </p>
        <p>
          The <code>address</code> attribute is duplicated as <code>listen</code>
          attribute in <code>graphics</code> element for backward compatibility.
          If both are provided they must be equal.
        </p>
6835 6836
      </dd>
      <dt><code>network</code></dt>
6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851
      <dd>
        <p>
          This is used to specify an existing network in the <code>network</code>
          attribute from libvirt's list of configured networks. The named network
          configuration will be examined to determine an appropriate listen
          address and the address will be stored in live XML in <code>address
          </code> attribute. For example, if the network has an IPv4 address in
          its configuration (e.g. if it has a forward type of <code>route</code>,
          <code>nat</code>, or no forward type (isolated)), the first IPv4
          address listed in the network's configuration will be used.
          If the network is describing a host bridge, the first IPv4 address
          associated with that bridge device will be used, and if the network is
          describing one of the 'direct' (macvtap) modes, the first IPv4 address
          of the first forward dev will be used.
        </p>
6852
      </dd>
6853
      <dt><code>socket</code> <span class="since">since 2.0.0 (QEMU only)</span></dt>
6854 6855 6856 6857 6858
      <dd>
        <p>
          This listen type tells a graphics server to listen on unix socket.
          Attribute <code>socket</code> contains a path to unix socket. If this
          attribute is omitted libvirt will generate this path for you.
6859
          Supported by graphics type <code>vnc</code> and <code>spice</code>.
6860 6861 6862 6863 6864 6865 6866
        </p>
        <p>
          For <code>vnc</code> graphics be backward compatible
          the <code>socket</code> attribute of first <code>listen</code> element
          is duplicated as <code>socket</code> attribute in <code>graphics</code>
          element. If <code>graphics</code> element contains a <code>socket</code>
          attribute all <code>listen</code> elements are ignored.
6867 6868
        </p>
      </dd>
6869
      <dt><code>none</code> <span class="since">since 2.0.0 (QEMU only)</span></dt>
P
Pavel Hrdina 已提交
6870 6871 6872 6873 6874 6875 6876
      <dd>
        <p>
          This listen type doesn't have any other attribute. Libvirt supports
          passing a file descriptor through our APIs virDomainOpenGraphics() and
          virDomainOpenGraphicsFD(). No other listen types are allowed if this
          one is used and the graphics device doesn't listen anywhere. You need
          to use one of the two APIs to pass a FD to QEMU in order to connect to
6877 6878
          this graphics device. Supported by graphics type <code>vnc</code> and
          <code>spice</code>.
P
Pavel Hrdina 已提交
6879 6880
        </p>
      </dd>
6881 6882
    </dl>

6883
    <h4><a id="elementsVideo">Video devices</a></h4>
6884 6885 6886 6887
    <p>
      A video device.
    </p>

6888
<pre>
6889 6890 6891 6892 6893 6894 6895 6896 6897
...
&lt;devices&gt;
  &lt;video&gt;
    &lt;model type='vga' vram='16384' heads='1'&gt;
      &lt;acceleration accel3d='yes' accel2d='yes'/&gt;
    &lt;/model&gt;
  &lt;/video&gt;
&lt;/devices&gt;
...</pre>
6898 6899 6900

    <dl>
      <dt><code>video</code></dt>
6901
      <dd>
6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915
        <p>
          The <code>video</code> element is the container for describing
          video devices. For backwards compatibility, if no <code>video</code>
          is set but there is a <code>graphics</code> in domain xml, then
          libvirt will add a default <code>video</code> according to the guest
          type.
        </p>
        <p>
          For a guest of type "kvm", the default <code>video</code> is:
          <code>type</code> with value "cirrus", <code>vram</code> with value
          "16384" and <code>heads</code> with value "1". By default, the first
          video device in domain xml is the primary one, but the optional
          attribute <code>primary</code> (<span class="since">since 1.0.2</span>)
          with value 'yes' can be used to mark the primary in cases of multiple
6916 6917
          video device. The non-primary must be type of "qxl" or
          (<span class="since">since 2.4.0</span>) "virtio".
6918
        </p>
6919
      </dd>
6920

6921 6922
      <dt><code>model</code></dt>
      <dd>
6923 6924 6925
        <p>
          The <code>model</code> element has a mandatory <code>type</code>
          attribute which takes the value "vga", "cirrus", "vmvga", "xen",
F
Fabian Freyer 已提交
6926
          "vbox", "qxl" (<span class="since">since 0.8.6</span>),
6927 6928 6929
          "virtio" (<span class="since">since 1.3.0</span>),
          "gop" (<span class="since">since 3.2.0</span>), or
          "none" (<span class="since">since 4.6.0</span>)
M
Marc-André Lureau 已提交
6930
          depending on the hypervisor features available.
6931 6932 6933 6934 6935 6936 6937 6938
          The purpose of the type <code>none</code> is to instruct libvirt not
          to add a default video device in the guest (see the paragraph above).
          This legacy behaviour can be inconvenient in cases where GPU mediated
          devices are meant to be the only rendering device within a guest and
          so specifying another <code>video</code> device along with type
          <code>none</code>.
          Refer to <a id="elementsHostDev">Host device assignment</a> to see
          how to add a mediated device into a guest.
6939 6940 6941 6942
        </p>
        <p>
          You can provide the amount of video memory in kibibytes (blocks of
          1024 bytes) using <code>vram</code>. This is supported only for guest
6943
          type of "libxl", "vz", "qemu", "vbox", "vmx" and "xen". If no
6944 6945 6946 6947 6948
          value is provided the default is used. If the size is not a power of
          two it will be rounded to closest one.
        </p>
        <p>
          The number of screen can be set using <code>heads</code>. This is
6949
          supported only for guests type of "vz", "kvm", "vbox" and "vmx".
6950 6951
        </p>
        <p>
6952 6953 6954
          For guest type of "kvm" or "qemu" and model type "qxl" there are
          optional attributes. Attribute <code>ram</code> (<span class="since">
          since 1.0.2</span>) specifies the size of the primary bar, while the
6955
          attribute <code>vram</code> specifies the secondary bar size.
6956 6957 6958 6959 6960
          If <code>ram</code> or <code>vram</code> are not supplied a default
          value is used. The <code>ram</code> should also be rounded to power of
          two as <code>vram</code>. There is also optional attribute
          <code>vgamem</code> (<span class="since">since 1.2.11</span>) to set
          the size of VGA framebuffer for fallback mode of QXL device.
6961
          Attribute <code>vram64</code> (<span class="since">since 1.3.3</span>)
6962
          extends secondary bar and makes it addressable as 64bit memory.
6963
        </p>
6964 6965 6966 6967
      </dd>

      <dt><code>acceleration</code></dt>
      <dd>
6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978
        Configure if video acceleration should be enabled.
        <dl>
        <dt><code>accel2d</code></dt>
        <dd>Enable 2D acceleration (for vbox driver only,
        <span class="since">since 0.7.1</span>)</dd>

        <dt><code>accel3d</code></dt>
        <dd>Enable 3D acceleration (for vbox driver
        <span class="since">since 0.7.1</span>, qemu driver
        <span class="since">since 1.3.0</span>)</dd>
        </dl>
6979
      </dd>
E
Eric Blake 已提交
6980 6981 6982 6983 6984

      <dt><code>address</code></dt>
      <dd>
        The optional <code>address</code> sub-element can be used to
        tie the video device to a particular PCI slot.
6985 6986 6987
        On S390, <code>address</code> can be used to provide the
        CCW address for the video device (<span class="since">
        since 4.2.0</span>).
E
Eric Blake 已提交
6988
      </dd>
J
Ján Tomko 已提交
6989 6990 6991 6992 6993 6994 6995 6996

      <dt><code>driver</code></dt>
      <dd>
        The subelement <code>driver</code> can be used to tune the device:
        <dl>
          <dt>virtio options</dt>
          <dd>
          <a href="#elementsVirtio">Virtio-specific options</a> can also be
6997 6998 6999 7000 7001 7002 7003 7004
          set (<span class="since">Since 3.5.0</span>)
          </dd>
          <dt>VGA configuration</dt>
          <dd>
          Control how the video devices exposed to the guest using the
          <code>vgaconf</code> attribute which takes the value "io", "on" or "off".
          At present, it's only applicable to the bhyve's "gop" video model type
          (<span class="since">Since 3.5.0</span>)
J
Ján Tomko 已提交
7005 7006 7007
          </dd>
        </dl>
      </dd>
D
Daniel P. Berrange 已提交
7008 7009
    </dl>

7010
    <h4><a id="elementsConsole">Consoles, serial, parallel &amp; channel devices</a></h4>
D
Daniel P. Berrange 已提交
7011 7012 7013

    <p>
      A character device provides a way to interact with the virtual machine.
7014 7015
      Paravirtualized consoles, serial ports, parallel ports and channels are
      all classed as character devices and so represented using the same syntax.
D
Daniel P. Berrange 已提交
7016 7017
    </p>

7018
<pre>
7019 7020 7021 7022 7023 7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037 7038 7039 7040 7041 7042 7043 7044
...
&lt;devices&gt;
  &lt;parallel type='pty'&gt;
    &lt;source path='/dev/pts/2'/&gt;
    &lt;target port='0'/&gt;
  &lt;/parallel&gt;
  &lt;serial type='pty'&gt;
    &lt;source path='/dev/pts/3'/&gt;
    &lt;target port='0'/&gt;
  &lt;/serial&gt;
  &lt;serial type='file'&gt;
    &lt;source path='/tmp/file' append='on'&gt;
      &lt;seclabel model='dac' relabel='no'/&gt;
    &lt;/source&gt;
    &lt;target port='0'/&gt;
  &lt;/serial&gt;
  &lt;console type='pty'&gt;
    &lt;source path='/dev/pts/4'/&gt;
    &lt;target port='0'/&gt;
  &lt;/console&gt;
  &lt;channel type='unix'&gt;
    &lt;source mode='bind' path='/tmp/guestfwd'/&gt;
    &lt;target type='guestfwd' address='10.0.2.1' port='4600'/&gt;
  &lt;/channel&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7045

7046 7047 7048 7049 7050
    <p>
      In each of these directives, the top-level element name (parallel, serial,
      console, channel) describes how the device is presented to the guest. The
      guest interface is configured by the <code>target</code> element.
    </p>
D
Daniel P. Berrange 已提交
7051

7052 7053 7054 7055 7056 7057
    <p>
      The interface presented to the host is given in the <code>type</code>
      attribute of the top-level element. The host interface is
      configured by the <code>source</code> element.
    </p>

7058 7059 7060 7061 7062 7063 7064 7065
    <p>
      The <code>source</code> element may contain an optional
      <code>seclabel</code> to override the way that labelling
      is done on the socket path.  If this element is not present,
      the <a href="#seclabel">security label is inherited from
        the per-domain setting</a>.
    </p>

7066 7067 7068 7069 7070 7071 7072 7073
    <p>
      If the interface <code>type</code> presented to the host is "file",
      then the <code>source</code> element may contain an optional attribute
      <code>append</code> that specifies whether or not the information in
      the file should be preserved on domain restart. Allowed values are
      "on" and "off" (default). <span class="since">Since 1.3.1</span>.
    </p>

7074
    <p>
B
Boris Fiuczynski 已提交
7075
      Regardless of the <code>type</code>, character devices can
7076 7077
      have an optional log file associated with them. This is
      expressed via a <code>log</code> sub-element, with a
B
Boris Fiuczynski 已提交
7078 7079 7080
      <code>file</code> attribute. There can also be an <code>append</code>
      attribute which takes the same values described above.
      <span class="since">Since 1.3.3</span>.
7081 7082 7083
    </p>

    <pre>
7084 7085 7086
...
&lt;log file="/var/log/libvirt/qemu/guestname-serial0.log" append="off"/&gt;
...</pre>
7087

E
Eric Blake 已提交
7088 7089 7090 7091 7092 7093 7094 7095
    <p>
      Each character device element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
      device to a
      particular <a href="#elementsControllers">controller</a> or PCI
      slot.
    </p>

7096 7097 7098 7099 7100 7101 7102 7103 7104 7105 7106
    <p>
      For character device with type <code>unix</code> or <code>tcp</code>
      the <code>source</code> has an optional element <code>reconnect</code>
      which configures reconnect timeout if the connection is lost.
      There are two attributes, <code>enabled</code> where possible
      values are "yes" and "no" and <code>timeout</code> which is in
      seconds. The <code>reconnect</code> attribute is valid only
      for <code>connect</code> mode.
      <span class="since">Since 3.7.0 (QEMU driver only)</span>.
    </p>

7107
    <h5><a id="elementsCharGuestInterface">Guest interface</a></h5>
7108 7109 7110 7111 7112 7113

    <p>
      A character device presents itself to the guest as one of the following
      types.
    </p>

7114
    <h6><a id="elementCharParallel">Parallel port</a></h6>
7115

7116
<pre>
7117 7118 7119 7120 7121 7122 7123 7124
...
&lt;devices&gt;
  &lt;parallel type='pty'&gt;
    &lt;source path='/dev/pts/2'/&gt;
    &lt;target port='0'/&gt;
  &lt;/parallel&gt;
&lt;/devices&gt;
...</pre>
7125 7126 7127

    <p>
      <code>target</code> can have a <code>port</code> attribute, which
7128
      specifies the port number. Ports are numbered starting from 0. There are
7129 7130 7131
      usually 0, 1 or 2 parallel ports.
    </p>

7132
    <h6><a id="elementCharSerial">Serial port</a></h6>
7133

7134
<pre>
7135 7136
...
&lt;devices&gt;
7137
  &lt;!-- Serial port --&gt;
7138 7139 7140 7141 7142
  &lt;serial type='pty'&gt;
    &lt;source path='/dev/pts/3'/&gt;
    &lt;target port='0'/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
7143 7144 7145 7146 7147 7148 7149
...</pre>

<pre>
...
&lt;devices&gt;
  &lt;!-- USB serial port --&gt;
  &lt;serial type='pty'&gt;
7150 7151 7152
    &lt;target type='usb-serial' port='0'&gt;
      &lt;model name='usb-serial'/&gt;
    &lt;/target&gt;
7153 7154 7155
    &lt;address type='usb' bus='0' port='1'/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
7156
...</pre>
7157 7158

    <p>
7159 7160 7161 7162 7163 7164
      The <code>target</code> element can have an optional <code>port</code>
      attribute, which specifies the port number (starting from 0), and an
      optional <code>type</code> attribute: valid values are,
      <span class="since">since 1.0.2</span>, <code>isa-serial</code> (usable
      with x86 guests), <code>usb-serial</code> (usable whenever USB support
      is available) and <code>pci-serial</code> (usable whenever PCI support
7165
      is available); <span class="since">since 3.10.0</span>,
7166
      <code>spapr-vio-serial</code> (usable with ppc64/pseries guests),
7167 7168
      <code>system-serial</code> (usable with aarch64/virt and,
      <span class="since">since 4.7.0</span>, riscv/virt guests) and
7169
      <code>sclp-serial</code> (usable with s390 and s390x guests) are
7170
      available as well.
7171 7172
    </p>

7173 7174 7175 7176 7177 7178 7179
    <p>
      <span class="since">Since 3.10.0</span>, the <code>target</code>
      element can have an optional <code>model</code> subelement;
      valid values for its <code>name</code> attribute are:
      <code>isa-serial</code> (usable with the <code>isa-serial</code> target
      type); <code>usb-serial</code> (usable with the <code>usb-serial</code>
      target type); <code>pci-serial</code>
7180 7181
      (usable with the <code>pci-serial</code> target type);
      <code>spapr-vty</code> (usable with the <code>spapr-vio-serial</code>
7182 7183 7184 7185 7186
      target type); <code>pl011</code> and,
      <span class="since">since 4.7.0</span>, <code>16550a</code> (usable
      with the <code>system-serial</code> target type);
      <code>sclpconsole</code> and <code>sclplmconsole</code> (usable with
      the <code>sclp-serial</code> target type).
7187 7188
    </p>

7189
    <p>
7190 7191
      If any of the attributes is not specified by the user, libvirt will
      choose a value suitable for most users.
7192 7193
    </p>

7194
    <p>
7195
      Most target types support configuring the guest-visible device
7196 7197
      address as <a href="#elementsAddress">documented above</a>; more
      specifically, acceptable address types are <code>isa</code> (for
7198 7199
      <code>isa-serial</code>), <code>usb</code> (for <code>usb-serial</code>),
      <code>pci</code> (for <code>pci-serial</code>) and <code>spapr-vio</code>
7200
      (for <code>spapr-vio-serial</code>). The <code>system-serial</code>
7201 7202
      and <code>sclp-serial</code> target types don't support specifying an
      address.
7203
    </p>
C
Cole Robinson 已提交
7204 7205

    <p>
7206 7207
      For the relationship between serial ports and consoles,
      <a href="#elementCharSerialAndConsole">see below</a>.
7208 7209
    </p>

7210 7211
    <h6><a id="elementCharConsole">Console</a></h6>

7212
<pre>
7213 7214
...
&lt;devices&gt;
7215
  &lt;!-- Serial console --&gt;
7216
  &lt;console type='pty'&gt;
7217
    &lt;source path='/dev/pts/2'/&gt;
7218
   &lt;target type='serial' port='0'/&gt;
7219
  &lt;/console&gt;
7220 7221
&lt;/devices&gt;
...</pre>
7222

7223 7224
<pre>
...
7225
&lt;devices&gt;
7226 7227 7228 7229 7230 7231 7232
  &lt;!-- KVM virtio console --&gt;
  &lt;console type='pty'&gt;
    &lt;source path='/dev/pts/5'/&gt;
    &lt;target type='virtio' port='0'/&gt;
  &lt;/console&gt;
&lt;/devices&gt;
...</pre>
7233

7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248
    <p>
      The <code>console</code> element is used to represent interactive
      serial consoles. Depending on the type of guest in use and the specifics
      of the configuration, the <code>console</code> element might represent
      the same device as an existing <code>serial</code> element or a separate
      device.
    </p>

    <p>
      A <code>target</code> subelement is supported and works the same
      way as with the <code>serial</code> element
      (<a href="#elementCharSerial">see above</a> for details).
      Valid values for the <code>type</code> attribute are:
      <code>serial</code> (described below);
      <code>virtio</code> (usable whenever VirtIO support is available);
M
Michal Privoznik 已提交
7249 7250 7251
      <code>xen</code>, <code>lxc</code> and <code>openvz</code>
      (available when the corresponding hypervisor is in use).
      <code>sclp</code> and <code>sclplm</code> (usable for s390 and
7252 7253 7254 7255
      s390x QEMU guests) are supported for compatibility reasons but should
      not be used for new guests: use the <code>sclpconsole</code> and
      <code>sclplmconsole</code> target models, respectively, with the
      <code>serial</code> element instead.
7256 7257 7258 7259 7260 7261 7262 7263 7264 7265 7266 7267 7268 7269 7270 7271 7272 7273 7274 7275 7276 7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288 7289 7290 7291 7292 7293 7294 7295 7296 7297 7298 7299 7300 7301 7302 7303 7304 7305 7306 7307 7308 7309 7310 7311 7312 7313 7314
    </p>

    <p>
      Of the target types listed above, <code>serial</code> is special in
      that it doesn't represents a separate device, but rather the same
      device as the first <code>serial</code> element. Due to this, there can
      only be a single <code>console</code> element with target type
      <code>serial</code> per guest.
    </p>

    <p>
      Virtio consoles are usually accessible as <code>/dev/hvc[0-7]</code>
      from inside the guest; for more information, see
      <a href="http://fedoraproject.org/wiki/Features/VirtioSerial">http://fedoraproject.org/wiki/Features/VirtioSerial</a>.
      <span class="since">Since 0.8.3</span>
    </p>

    <p>
      For the relationship between serial ports and consoles,
      <a href="#elementCharSerialAndConsole">see below</a>.
    </p>

    <h6><a id="elementCharSerialAndConsole">Relationship between serial ports and consoles</a></h6>

    <p>
      Due to hystorical reasons, the <code>serial</code> and
      <code>console</code> elements have partially overlapping scopes.
    </p>

    <p>
      In general, both elements are used to configure one or more serial
      consoles to be used for interacting with the guest. The main difference
      between the two is that <code>serial</code> is used for emulated,
      usually native, serial consoles, whereas <code>console</code> is used
      for paravirtualized ones.
    </p>

    <p>
      Both emulated and paravirtualized serial consoles have advantages and
      disadvantages:
    </p>

    <ul>
      <li>
        emulated serial consoles are usually initialized much earlier than
        paravirtualized ones, so they can be used to control the bootloader
        and display both firmware and early boot messages;
      </li>
      <li>
        on several platforms, there can only be a single emulated serial
        console per guest but paravirtualized consoles don't suffer from the
        same limitation.
      </li>
    </ul>

    <p>
      A configuration such as:
    </p>

7315
<pre>
7316
...
7317
&lt;devices&gt;
7318 7319 7320
  &lt;console type='pty'&gt;
    &lt;target type='serial'/&gt;
  &lt;/console&gt;
7321
  &lt;console type='pty'&gt;
7322
    &lt;target type='virtio'/&gt;
7323 7324 7325
  &lt;/console&gt;
&lt;/devices&gt;
...</pre>
7326

7327
    <p>
7328 7329 7330 7331 7332 7333 7334 7335 7336 7337 7338 7339 7340 7341
      will work on any platform and will result in one emulated serial console
      for early boot logging / interactive / recovery use, and one
      paravirtualized serial console to be used eg. as a side channel. Most
      people will be fine with having just the first <code>console</code>
      element in their configuration.
    </p>

    <p>
      Note that, due to the compatibility concerns mentioned earlier, all the
      following configurations:
    </p>

<pre>
...
7342
&lt;devices&gt;
7343 7344 7345 7346 7347 7348
  &lt;serial type='pty'/&gt;
&lt;/devices&gt;
...</pre>

<pre>
...
7349
&lt;devices&gt;
7350 7351 7352 7353 7354 7355
  &lt;console type='pty'/&gt;
&lt;/devices&gt;
...</pre>

<pre>
...
7356
&lt;devices&gt;
7357 7358 7359 7360 7361 7362 7363 7364
  &lt;serial type='pty'/&gt;
  &lt;console type='pty'/&gt;
&lt;/devices&gt;
...</pre>

    <p>
      will be treated the same and will result in a single emulated serial
      console being available to the guest.
7365 7366
    </p>

7367
    <h6><a id="elementCharChannel">Channel</a></h6>
7368 7369 7370 7371 7372 7373

    <p>
      This represents a private communication channel between the host and the
      guest.
    </p>

7374
<pre>
7375 7376 7377 7378 7379 7380 7381 7382 7383 7384 7385 7386 7387 7388 7389 7390 7391 7392 7393 7394
...
&lt;devices&gt;
  &lt;channel type='unix'&gt;
    &lt;source mode='bind' path='/tmp/guestfwd'/&gt;
    &lt;target type='guestfwd' address='10.0.2.1' port='4600'/&gt;
  &lt;/channel&gt;

  &lt;!-- KVM virtio channel --&gt;
  &lt;channel type='pty'&gt;
    &lt;target type='virtio' name='arbitrary.virtio.serial.port.name'/&gt;
  &lt;/channel&gt;
  &lt;channel type='unix'&gt;
    &lt;source mode='bind' path='/var/lib/libvirt/qemu/f16x86_64.agent'/&gt;
    &lt;target type='virtio' name='org.qemu.guest_agent.0' state='connected'/&gt;
  &lt;/channel&gt;
  &lt;channel type='spicevmc'&gt;
    &lt;target type='virtio' name='com.redhat.spice.0'/&gt;
  &lt;/channel&gt;
&lt;/devices&gt;
...</pre>
7395 7396 7397 7398 7399 7400 7401 7402 7403 7404 7405 7406 7407 7408

    <p>
      This can be implemented in a variety of ways. The specific type of
      channel is given in the <code>type</code> attribute of the
      <code>target</code> element. Different channel types have different
      <code>target</code> attributes.
    </p>

    <dl>
      <dt><code>guestfwd</code></dt>
      <dd>TCP traffic sent by the guest to a given IP address and port is
        forwarded to the channel device on the host. The <code>target</code>
        element must have <code>address</code> and <code>port</code> attributes.
        <span class="since">Since 0.7.3</span></dd>
7409 7410 7411

      <dt><code>virtio</code></dt>
      <dd>Paravirtualized virtio channel. Channel is exposed in the guest under
E
Eric Blake 已提交
7412
        /dev/vport*, and if the optional element <code>name</code> is specified,
7413
        /dev/virtio-ports/$name (for more info, please see
E
Eric Blake 已提交
7414 7415
        <a href="http://fedoraproject.org/wiki/Features/VirtioSerial">http://fedoraproject.org/wiki/Features/VirtioSerial</a>). The
        optional element <code>address</code> can tie the channel to a
7416 7417
        particular <code>type='virtio-serial'</code>
        controller, <a href="#elementsAddress">documented above</a>.
D
Daniel P. Berrange 已提交
7418 7419 7420 7421
        With qemu, if <code>name</code> is "org.qemu.guest_agent.0",
        then libvirt can interact with a guest agent installed in the
        guest, for actions such as guest shutdown or file system quiescing.
        <span class="since">Since 0.7.7, guest agent interaction
7422
        since 0.9.10</span> Moreover, <span class="since">since 1.0.6</span>
7423 7424 7425 7426
        it is possible to have source path auto generated for virtio unix channels.
        This is very useful in case of a qemu guest agent, where users don't
        usually care about the source path since it's libvirt who talks to
        the guest agent. In case users want to utilize this feature, they should
7427 7428 7429 7430 7431 7432
        leave <code>&lt;source&gt;</code> element out. <span class="since">Since
        1.2.11</span> the active XML for a virtio channel may contain an optional
        <code>state</code> attribute that reflects whether a process in the
        guest is active on the channel. This is an output-only attribute.
        Possible values for the <code>state</code> attribute are
        <code>connected</code> and <code>disconnected</code>.
7433
      </dd>
J
Joao Martins 已提交
7434 7435 7436 7437 7438 7439 7440 7441 7442 7443
      <dt><code>xen</code></dt>
      <dd> Paravirtualized Xen channel. Channel is exposed in the guest as a
        Xen console but identified with a name. Setup and consumption of a Xen
        channel depends on software and configuration in the guest
        (for more info, please see <a href="http://xenbits.xen.org/docs/unstable/misc/channel.txt">http://xenbits.xen.org/docs/unstable/misc/channel.txt</a>).
        Channel source path semantics are the same as the virtio target type.
        The <code>state</code> attribute is not supported since Xen channels
        lack the necessary probing mechanism.
        <span class="since">Since 2.3.0</span>
      </dd>
7444 7445 7446 7447 7448 7449 7450 7451 7452 7453 7454 7455 7456
      <dt><code>spicevmc</code></dt>
      <dd>Paravirtualized SPICE channel. The domain must also have a
        SPICE server as a <a href="#elementsGraphics">graphics
        device</a>, at which point the host piggy-backs messages
        across the <code>main</code> channel.  The <code>target</code>
        element must be present, with
        attribute <code>type='virtio'</code>; an optional
        attribute <code>name</code> controls how the guest will have
        access to the channel, and defaults
        to <code>name='com.redhat.spice.0'</code>.  The
        optional <code>address</code> element can tie the channel to a
        particular <code>type='virtio-serial'</code> controller.
        <span class="since">Since 0.8.8</span></dd>
7457 7458
    </dl>

7459
    <h5><a id="elementsCharHostInterface">Host interface</a></h5>
7460 7461 7462 7463 7464

    <p>
      A character device presents itself to the host as one of the following
      types.
    </p>
D
Daniel P. Berrange 已提交
7465

7466
    <h6><a id="elementsCharSTDIO">Domain logfile</a></h6>
D
Daniel P. Berrange 已提交
7467 7468 7469 7470 7471 7472

    <p>
      This disables all input on the character device, and sends output
      into the virtual machine's logfile
    </p>

7473
<pre>
7474 7475 7476 7477 7478 7479 7480
...
&lt;devices&gt;
  &lt;console type='stdio'&gt;
    &lt;target port='1'/&gt;
  &lt;/console&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7481 7482


7483
    <h6><a id="elementsCharFle">Device logfile</a></h6>
D
Daniel P. Berrange 已提交
7484 7485 7486 7487 7488 7489

    <p>
      A file is opened and all data sent to the character
      device is written to the file.
    </p>

7490
<pre>
7491 7492 7493 7494 7495 7496 7497 7498
...
&lt;devices&gt;
  &lt;serial type="file"&gt;
    &lt;source path="/var/log/vm/vm-serial.log"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7499

7500
    <h6><a id="elementsCharVC">Virtual console</a></h6>
D
Daniel P. Berrange 已提交
7501 7502 7503 7504 7505 7506 7507

    <p>
      Connects the character device to the graphical framebuffer in
      a virtual console. This is typically accessed via a special
      hotkey sequence such as "ctrl+alt+3"
    </p>

7508
<pre>
7509 7510 7511 7512 7513 7514 7515
...
&lt;devices&gt;
  &lt;serial type='vc'&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7516

7517
    <h6><a id="elementsCharNull">Null device</a></h6>
D
Daniel P. Berrange 已提交
7518 7519 7520 7521 7522 7523

    <p>
      Connects the character device to the void. No data is ever
      provided to the input. All data written is discarded.
    </p>

7524
<pre>
7525 7526 7527 7528 7529 7530 7531
...
&lt;devices&gt;
  &lt;serial type='null'&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7532

7533
    <h6><a id="elementsCharPTY">Pseudo TTY</a></h6>
D
Daniel P. Berrange 已提交
7534 7535 7536 7537 7538 7539 7540

    <p>
      A Pseudo TTY is allocated using /dev/ptmx. A suitable client
      such as 'virsh console' can connect to interact with the
      serial port locally.
    </p>

7541
<pre>
7542 7543 7544 7545 7546 7547 7548 7549
...
&lt;devices&gt;
  &lt;serial type="pty"&gt;
    &lt;source path="/dev/pts/3"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7550 7551 7552

    <p>
      NB special case if &lt;console type='pty'&gt;, then the TTY
A
Atsushi SAKAI 已提交
7553
      path is also duplicated as an attribute tty='/dev/pts/3'
D
Daniel P. Berrange 已提交
7554 7555 7556 7557
      on the top level &lt;console&gt; tag. This provides compat
      with existing syntax for &lt;console&gt; tags.
    </p>

7558
    <h6><a id="elementsCharHost">Host device proxy</a></h6>
D
Daniel P. Berrange 已提交
7559 7560 7561 7562 7563

    <p>
      The character device is passed through to the underlying
      physical character device. The device types must match,
      eg the emulated serial port should only be connected to
A
Atsushi SAKAI 已提交
7564
      a host serial port - don't connect a serial port to a parallel
D
Daniel P. Berrange 已提交
7565 7566 7567
      port.
    </p>

7568
<pre>
7569 7570 7571 7572 7573 7574 7575 7576
...
&lt;devices&gt;
  &lt;serial type="dev"&gt;
    &lt;source path="/dev/ttyS0"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7577

7578
    <h6><a id="elementsCharPipe">Named pipe</a></h6>
7579 7580 7581 7582 7583 7584

    <p>
      The character device writes output to a named pipe. See pipe(7) for
      more info.
    </p>

7585
<pre>
7586 7587 7588 7589 7590 7591 7592 7593
...
&lt;devices&gt;
  &lt;serial type="pipe"&gt;
    &lt;source path="/tmp/mypipe"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
7594

7595
    <h6><a id="elementsCharTCP">TCP client/server</a></h6>
D
Daniel P. Berrange 已提交
7596 7597 7598

    <p>
      The character device acts as a TCP client connecting to a
7599
      remote server.
D
Daniel P. Berrange 已提交
7600 7601
    </p>

7602
<pre>
7603 7604 7605 7606 7607 7608 7609 7610 7611
...
&lt;devices&gt;
  &lt;serial type="tcp"&gt;
    &lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
    &lt;protocol type="raw"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
 ...</pre>
7612 7613 7614 7615 7616

    <p>
      Or as a TCP server waiting for a client connection.
    </p>

7617
<pre>
7618 7619 7620 7621 7622 7623 7624 7625 7626
...
&lt;devices&gt;
  &lt;serial type="tcp"&gt;
    &lt;source mode="bind" host="127.0.0.1" service="2445"/&gt;
    &lt;protocol type="raw"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
7627 7628

    <p>
E
Eric Blake 已提交
7629
      Alternatively you can use <code>telnet</code> instead
J
John Ferlan 已提交
7630 7631 7632 7633 7634 7635 7636
      of <code>raw</code> TCP in order to utilize the telnet protocol
      for the connection.
    </p>
    <p>
      <span class="since">Since 0.8.5,</span> some hypervisors support
      use of either <code>telnets</code> (secure telnet) or <code>tls</code>
      (via secure sockets layer) as the transport protocol for connections.
E
Eric Blake 已提交
7637
    </p>
7638

7639
<pre>
7640 7641 7642 7643 7644 7645 7646
...
&lt;devices&gt;
  &lt;serial type="tcp"&gt;
    &lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
    &lt;protocol type="telnet"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
7647
  ...
7648 7649 7650 7651 7652 7653 7654
  &lt;serial type="tcp"&gt;
    &lt;source mode="bind" host="127.0.0.1" service="2445"/&gt;
    &lt;protocol type="telnet"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
7655 7656 7657 7658 7659 7660 7661 7662 7663 7664 7665 7666 7667 7668 7669 7670 7671 7672 7673

    <p>
      <span class="since">Since 2.4.0,</span> the optional attribute
      <code>tls</code> can be used to control whether a chardev
      TCP communication channel would utilize a hypervisor configured
      TLS X.509 certificate environment in order to encrypt the data
      channel. For the QEMU hypervisor, usage of a TLS environment can
      be controlled on the host by the <code>chardev_tls</code> and
      <code>chardev_tls_x509_cert_dir</code> or
      <code>default_tls_x509_cert_dir</code> settings in the file
      /etc/libvirt/qemu.conf. If <code>chardev_tls</code> is enabled,
      then unless the <code>tls</code> attribute is set to "no", libvirt
      will use the host configured TLS environment.
      If <code>chardev_tls</code> is disabled, but the <code>tls</code>
      attribute is set to "yes", then libvirt will attempt to use the
      host TLS environment if either the <code>chardev_tls_x509_cert_dir</code>
      or <code>default_tls_x509_cert_dir</code> TLS directory structure exists.
    </p>
<pre>
7674 7675 7676 7677 7678 7679 7680 7681 7682
...
&lt;devices&gt;
  &lt;serial type="tcp"&gt;
    &lt;source mode='connect' host="127.0.0.1" service="5555" tls="yes"/&gt;
    &lt;protocol type="raw"/&gt;
    &lt;target port="0"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7683

7684
    <h6><a id="elementsCharUDP">UDP network console</a></h6>
D
Daniel P. Berrange 已提交
7685 7686 7687 7688 7689 7690

    <p>
      The character device acts as a UDP netconsole service,
      sending and receiving packets. This is a lossy service.
    </p>

7691
<pre>
7692 7693 7694 7695 7696 7697 7698 7699 7700
...
&lt;devices&gt;
  &lt;serial type="udp"&gt;
    &lt;source mode="bind" host="0.0.0.0" service="2445"/&gt;
    &lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7701

7702
    <h6><a id="elementsCharUNIX">UNIX domain socket client/server</a></h6>
D
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7703 7704 7705 7706 7707 7708

    <p>
      The character device acts as a UNIX domain socket server,
      accepting connections from local clients.
    </p>

7709
<pre>
7710 7711 7712 7713 7714 7715 7716 7717
...
&lt;devices&gt;
  &lt;serial type="unix"&gt;
    &lt;source mode="bind" path="/tmp/foo"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
Daniel P. Berrange 已提交
7718

7719
    <h6><a id="elementsCharSpiceport">Spice channel</a></h6>
7720 7721 7722 7723 7724 7725

    <p>
      The character device is accessible through spice connection
      under a channel name specified in the <code>channel</code>
      attribute.  <span class="since">Since 1.2.2</span>
    </p>
7726 7727 7728 7729 7730
    <p>
      Note: depending on the hypervisor, spiceports might (or might not)
      be enabled on domains with or without <a href="#elementsGraphics">spice
      graphics</a>.
    </p>
7731 7732

<pre>
7733 7734 7735 7736 7737 7738 7739 7740
...
&lt;devices&gt;
  &lt;serial type="spiceport"&gt;
    &lt;source channel="org.qemu.console.serial.0"/&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
7741

7742
    <h6><a id="elementsNmdm">Nmdm device</a></h6>
7743 7744 7745

    <p>
      The nmdm device driver, available on FreeBSD, provides two
C
Chen Hanxiao 已提交
7746
      tty devices connected together by a virtual null modem cable.
7747 7748 7749 7750
      <span class="since">Since 1.2.4</span>
    </p>

<pre>
7751 7752 7753 7754 7755 7756 7757
...
&lt;devices&gt;
  &lt;serial type="nmdm"&gt;
    &lt;source master="/dev/nmdm0A" slave="/dev/nmdm0B"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
7758 7759 7760 7761 7762 7763 7764

    <p>
      The <code>source</code> element has these attributes:
    </p>

    <dl>
      <dt><code>master</code></dt>
7765 7766
      <dd>Master device of the pair, that is passed to the hypervisor.
      Device is specified by a fully qualified path.</dd>
7767 7768 7769

      <dt><code>slave</code></dt>
      <dd>Slave device of the pair, that is passed to the clients for connection
7770
      to the guest console. Device is specified by a fully qualified path.</dd>
7771
    </dl>
7772

7773
    <h4><a id="elementsSound">Sound devices</a></h4>
7774 7775 7776 7777 7778 7779

    <p>
      A virtual sound card can be attached to the host via the
      <code>sound</code> element. <span class="since">Since 0.4.3</span>
    </p>

7780
<pre>
7781 7782 7783 7784 7785
...
&lt;devices&gt;
  &lt;sound model='es1370'/&gt;
&lt;/devices&gt;
...</pre>
7786 7787 7788 7789 7790 7791 7792

    <dl>
      <dt><code>sound</code></dt>
      <dd>
        The <code>sound</code> element has one mandatory attribute,
        <code>model</code>, which specifies what real sound device is emulated.
        Valid values are specific to the underlying hypervisor, though typical
7793
        choices are 'es1370', 'sb16', 'ac97', 'ich6' and 'usb'.
7794
        (<span class="since">
7795 7796
         'ac97' only since 0.6.0, 'ich6' only since 0.8.8,
         'usb' only since 1.2.7</span>)
7797 7798 7799
      </dd>
    </dl>

7800 7801 7802 7803 7804
    <p>
      <span class="since">Since 0.9.13</span>, a sound element
      with <code>ich6</code> model can have optional
      sub-elements <code>&lt;codec&gt;</code> to attach various audio
      codecs to the audio device. If not specified, a default codec
F
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7805 7806 7807 7808 7809 7810 7811 7812 7813 7814 7815 7816
      will be attached to allow playback and recording.
      </p>
      <p>
      Valid values are:
      </p>
      <p>
      <ul>
        <li>'duplex' - advertise a line-in and a line-out </li>
        <li>'micro' -  advertise a speaker and a microphone </li>
        <li>'output' - advertise a line-out
            <span class="since">Since 4.4.0</span></li>
      </ul>
7817 7818 7819
    </p>

<pre>
7820 7821 7822 7823 7824 7825 7826
...
&lt;devices&gt;
  &lt;sound model='ich6'&gt;
    &lt;codec type='micro'/&gt;
  &lt;/sound&gt;
&lt;/devices&gt;
...</pre>
7827

E
Eric Blake 已提交
7828 7829 7830
    <p>
      Each <code>sound</code> element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
7831 7832
      device to a particular PCI
      slot, <a href="#elementsAddress">documented above</a>.
E
Eric Blake 已提交
7833 7834
    </p>

7835
    <h4><a id="elementsWatchdog">Watchdog device</a></h4>
R
Richard Jones 已提交
7836 7837 7838 7839 7840 7841 7842 7843 7844 7845 7846 7847 7848 7849 7850 7851 7852 7853 7854

    <p>
      A virtual hardware watchdog device can be added to the guest via
      the <code>watchdog</code> element.
      <span class="since">Since 0.7.3, QEMU and KVM only</span>
    </p>

    <p>
      The watchdog device requires an additional driver and management
      daemon in the guest.  Just enabling the watchdog in the libvirt
      configuration does not do anything useful on its own.
    </p>

    <p>
      Currently libvirt does not support notification when the
      watchdog fires.  This feature is planned for a future version of
      libvirt.
    </p>

7855
<pre>
7856 7857 7858 7859 7860
...
&lt;devices&gt;
  &lt;watchdog model='i6300esb'/&gt;
&lt;/devices&gt;
...</pre>
R
Richard Jones 已提交
7861

7862 7863 7864 7865 7866 7867
<pre>
  ...
  &lt;devices&gt;
    &lt;watchdog model='i6300esb' action='poweroff'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>
R
Richard Jones 已提交
7868 7869 7870 7871

    <dl>
      <dt><code>model</code></dt>
      <dd>
M
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7872
        <p>
R
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7873
        The required <code>model</code> attribute specifies what real
M
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7874 7875 7876 7877 7878 7879 7880
        watchdog device is emulated.  Valid values are specific to the
        underlying hypervisor.
        </p>
        <p>
        QEMU and KVM support:
        </p>
        <ul>
7881
          <li>'i6300esb' - the recommended device,
M
Matthew Booth 已提交
7882
            emulating a PCI Intel 6300ESB </li>
7883 7884
          <li>'ib700' - emulating an ISA iBase IB700 </li>
          <li>'diag288' - emulating an S390 DIAG288 device
7885
            <span class="since">Since 1.2.17</span></li>
M
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7886
        </ul>
R
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7887 7888 7889
      </dd>
      <dt><code>action</code></dt>
      <dd>
M
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7890
        <p>
R
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7891
        The optional <code>action</code> attribute describes what
M
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7892 7893 7894 7895 7896 7897 7898
        action to take when the watchdog expires.  Valid values are
        specific to the underlying hypervisor.
        </p>
        <p>
        QEMU and KVM support:
        </p>
        <ul>
7899 7900
          <li>'reset' - default, forcefully reset the guest</li>
          <li>'shutdown' - gracefully shutdown the guest
M
Matthew Booth 已提交
7901
            (not recommended) </li>
7902 7903 7904 7905
          <li>'poweroff' - forcefully power off the guest</li>
          <li>'pause' - pause the guest</li>
          <li>'none' - do nothing</li>
          <li>'dump' - automatically dump the guest
7906
            <span class="since">Since 0.8.7</span></li>
7907
          <li>'inject-nmi' - inject a non-maskable interrupt
7908
            into the guest
7909
            <span class="since">Since 1.2.17</span></li>
M
Matthew Booth 已提交
7910 7911
        </ul>
        <p>
7912
        Note 1: the 'shutdown' action requires that the guest
M
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7913 7914 7915 7916 7917
        is responsive to ACPI signals.  In the sort of situations
        where the watchdog has expired, guests are usually unable
        to respond to ACPI signals.  Therefore using 'shutdown'
        is not recommended.
        </p>
7918 7919 7920 7921
        <p>
        Note 2: the directory to save dump files can be configured
        by <code>auto_dump_path</code> in file /etc/libvirt/qemu.conf.
        </p>
R
Richard Jones 已提交
7922 7923 7924
      </dd>
    </dl>

7925
    <h4><a id="elementsMemBalloon">Memory balloon device</a></h4>
7926 7927 7928 7929 7930 7931 7932 7933

    <p>
      A virtual memory balloon device is added to all Xen and KVM/QEMU
      guests. It will be seen as <code>memballoon</code> element.
      It will be automatically added when appropriate, so there is no
      need to explicitly add this element in the guest XML unless a
      specific PCI slot needs to be assigned.
      <span class="since">Since 0.8.3, Xen, QEMU and KVM only</span>
7934 7935 7936
      Additionally, <span class="since">since 0.8.4</span>, if the
      memballoon device needs to be explicitly disabled,
      <code>model='none'</code> may be used.
7937 7938 7939
    </p>

    <p>
J
Ján Tomko 已提交
7940
      Example: automatically added device with KVM
7941 7942
    </p>
<pre>
7943 7944 7945 7946 7947
...
&lt;devices&gt;
  &lt;memballoon model='virtio'/&gt;
&lt;/devices&gt;
...</pre>
7948 7949

    <p>
J
Ján Tomko 已提交
7950
      Example: manually added device with static PCI slot 2 requested
7951 7952 7953 7954
    </p>
<pre>
  ...
  &lt;devices&gt;
J
Ján Tomko 已提交
7955 7956
    &lt;memballoon model='virtio'&gt;
      &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/&gt;
7957
      &lt;stats period='10'/&gt;
7958
      &lt;driver iommu='on' ats='on'/&gt;
J
Ján Tomko 已提交
7959
    &lt;/memballoon&gt;
7960 7961 7962 7963 7964 7965 7966 7967
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The required <code>model</code> attribute specifies what type
E
Eric Blake 已提交
7968 7969
          of balloon device is provided. Valid values are specific to
          the virtualization platform
7970 7971
        </p>
        <ul>
7972
          <li>'virtio' - default with QEMU/KVM</li>
7973 7974
          <li>'virtio-transitional' <span class="since">Since 5.2.0</span></li>
          <li>'virtio-non-transitional' <span class="since">Since 5.2.0</span></li>
7975
          <li>'xen' - default with Xen</li>
7976
        </ul>
7977 7978
        See <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
        for more details.
7979
      </dd>
7980 7981 7982 7983 7984 7985 7986 7987 7988 7989
      <dt><code>autodeflate</code></dt>
      <dd>
        <p>
          The optional <code>autodeflate</code> attribute allows to
          enable/disable (values "on"/"off", respectively) the ability of the
          QEMU virtio memory balloon to release some memory at the last moment
          before a guest's process get killed by Out of Memory killer.
          <span class="since">Since 1.3.1, QEMU and KVM only</span>
        </p>
      </dd>
7990 7991 7992
      <dt><code>period</code></dt>
      <dd>
        <p>
7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003
          The optional <code>period</code> allows the QEMU virtio memory balloon
          driver to provide statistics through the <code>virsh dommemstat
          [domain]</code> command. By default, collection is not enabled. In
          order to enable, use the <code>virsh dommemstat [domain] --period
          [number]</code> command or <code>virsh edit</code> command to add the
          option to the XML definition.  The <code>virsh dommemstat</code> will
          accept the options <code>--live</code>, <code>--current</code>,
          or <code>--config</code>.  If an option is not provided, the change
          for a running domain will only be made to the active guest.  If the
          QEMU driver is not at the right revision, the attempt to set the
          period will fail.  Large values (e.g. many years) might be ignored.
8004 8005 8006
          <span class='since'>Since 1.1.1, requires QEMU 1.5</span>
        </p>
      </dd>
8007 8008 8009 8010 8011 8012
      <dt><code>driver</code></dt>
      <dd>
        For model <code>virtio</code> memballoon,
        <a href="#elementsVirtio">Virtio-specific options</a> can also be
        set. (<span class="since">Since 3.5.0</span>)
      </dd>
8013
    </dl>
8014
    <h4><a id="elementsRng">Random number generator device</a></h4>
8015 8016 8017 8018 8019 8020 8021 8022 8023 8024 8025

    <p>
      The virtual random number generator device allows the host to pass
      through entropy to guest operating systems.
      <span class="since">Since 1.0.3</span>
    </p>

    <p>
      Example: usage of the RNG device:
    </p>
<pre>
8026 8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038
...
&lt;devices&gt;
  &lt;rng model='virtio'&gt;
    &lt;rate period="2000" bytes="1234"/&gt;
    &lt;backend model='random'&gt;/dev/random&lt;/backend&gt;
    &lt;!-- OR --&gt;
    &lt;backend model='egd' type='udp'&gt;
      &lt;source mode='bind' service='1234'/&gt;
      &lt;source mode='connect' host='1.2.3.4' service='1234'/&gt;
    &lt;/backend&gt;
  &lt;/rng&gt;
&lt;/devices&gt;
...
8039 8040 8041 8042 8043 8044 8045 8046 8047 8048
</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The required <code>model</code> attribute specifies what type
          of RNG device is provided. Valid values are specific to
          the virtualization platform:
        </p>
        <ul>
8049
          <li>'virtio' - supported by qemu and virtio-rng kernel module</li>
8050 8051
          <li>'virtio-transitional' <span class='since'>Since 5.2.0</span></li>
          <li>'virtio-non-transitional' <span class='since'>Since 5.2.0</span></li>
8052
        </ul>
8053 8054
        See <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
        for more details.
8055
      </dd>
8056 8057 8058 8059 8060 8061 8062 8063 8064 8065 8066 8067
      <dt><code>rate</code></dt>
      <dd>
        <p>
          The optional <code>rate</code> element allows limiting the rate at
          which entropy can be consumed from the source.  The mandatory
          attribute <code>bytes</code> specifies how many bytes are permitted
          to be consumed per period.  An optional <code>period</code> attribute
          specifies the duration of a period in milliseconds; if omitted, the
          period is taken as 1000 milliseconds (1 second).
          <span class='since'>Since 1.0.4</span>
        </p>
      </dd>
8068 8069 8070 8071 8072 8073 8074
      <dt><code>backend</code></dt>
      <dd>
        <p>
          The <code>backend</code> element specifies the source of entropy
          to be used for the domain. The source model is configured using the
          <code>model</code> attribute. Supported source models are:
        </p>
8075 8076 8077 8078
        <dl>
          <dt><code>random</code></dt>
          <dd>
            <p>
8079 8080 8081 8082 8083 8084 8085 8086 8087 8088
              This backend type expects a non-blocking character device
              as input. The file name is specified as contents of the
              <code>backend</code> element. <span class='since'>Since
              1.3.4</span> any path is accepted. Before that
              <code>/dev/random</code> and <code>/dev/hwrng</code> were
              the only accepted paths. When no file name is specified,
              the hypervisor default is used. For QEMU, the default is
              <code>/dev/random</code>. However, the recommended source
              of entropy is <code>/dev/urandom</code> (as it doesn't
              have the limitations of <code>/dev/random</code>).
8089 8090 8091 8092 8093 8094 8095 8096 8097 8098 8099 8100
            </p>
          </dd>
          <dt><code>egd</code></dt>
          <dd>
            <p>
              This backend connects to a source using the EGD protocol.
              The source is specified as a character device. Refer to
              <a href='#elementsCharHostInterface'>character device host interface</a>
              for more information.
            </p>
          </dd>
        </dl>
8101
      </dd>
8102 8103 8104 8105 8106 8107 8108 8109 8110 8111 8112
      <dt><code>driver</code></dt>
      <dd>
        The subelement <code>driver</code> can be used to tune the device:
        <dl>
          <dt>virtio options</dt>
          <dd>
          <a href="#elementsVirtio">Virtio-specific options</a> can also be
          set. (<span class="since">Since 3.5.0</span>)
          </dd>
        </dl>
      </dd>
8113 8114

    </dl>
8115

8116
    <h4><a id="elementsTpm">TPM device</a></h4>
8117 8118 8119

    <p>
      The TPM device enables a QEMU guest to have access to TPM
8120
      functionality. The TPM device may either be a TPM 1.2 or
8121
      a TPM 2.0.
8122 8123 8124
    </p>
    <p>
      The TPM passthrough device type provides access to the host's TPM
8125
      for one QEMU guest. No other software may be using the TPM device,
8126 8127 8128 8129 8130 8131 8132 8133
      typically /dev/tpm0, at the time the QEMU guest is started.
      <span class="since">'passthrough' since 1.0.5</span>
    </p>

    <p>
     Example: usage of the TPM passthrough device
    </p>
<pre>
8134 8135 8136 8137 8138 8139 8140 8141 8142
...
&lt;devices&gt;
  &lt;tpm model='tpm-tis'&gt;
    &lt;backend type='passthrough'&gt;
      &lt;device path='/dev/tpm0'/&gt;
    &lt;/backend&gt;
  &lt;/tpm&gt;
&lt;/devices&gt;
...
8143 8144 8145 8146 8147 8148 8149 8150 8151 8152 8153 8154 8155 8156 8157
</pre>

    <p>
      The emulator device type gives access to a TPM emulator providing
      TPM functionality for each VM. QEMU talks to it over a Unix socket. With
      the emulator device type each guest gets its own private TPM.
      <span class="since">'emulator' since 4.5.0</span>
    </p>
    <p>
     Example: usage of the TPM Emulator
    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;tpm model='tpm-tis'&gt;
8158
      &lt;backend type='emulator' version='2.0'&gt;
8159 8160 8161 8162
      &lt;/backend&gt;
    &lt;/tpm&gt;
  &lt;/devices&gt;
  ...
8163 8164 8165 8166 8167 8168 8169 8170
</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The <code>model</code> attribute specifies what device
          model QEMU provides to the guest. If no model name is provided,
          <code>tpm-tis</code> will automatically be chosen.
8171 8172
          <span class="since">Since 4.4.0</span>, another available choice
          is the <code>tpm-crb</code>, which should only be used when the
8173
          backend device is a TPM 2.0.
8174 8175 8176 8177 8178 8179 8180 8181
        </p>
      </dd>
      <dt><code>backend</code></dt>
      <dd>
        <p>
          The <code>backend</code> element specifies the type of
          TPM device. The following types are supported:
        </p>
8182 8183 8184 8185 8186 8187 8188 8189 8190 8191 8192 8193 8194 8195 8196
        <dl>
          <dt><code>passthrough</code></dt>
          <dd>
            <p>
              Use the host's TPM device.
            </p>
            <p>
              This backend type requires exclusive access to a TPM device on
              the host. An example for such a device is /dev/tpm0. The fully
              qualified file name is specified by path attribute of the
              <code>source</code> element. If no file name is specified then
              /dev/tpm0 is automatically used.
            </p>
          </dd>
        </dl>
8197 8198 8199 8200 8201 8202 8203 8204 8205 8206
        <dl>
          <dt><code>emulator</code></dt>
          <dd>
            <p>
              For this backend type the 'swtpm' TPM Emulator must be installed on the
              host. Libvirt will automatically start an independent TPM emulator
              for each QEMU guest requesting access to it.
            </p>
          </dd>
        </dl>
8207
      </dd>
8208 8209 8210 8211 8212 8213 8214 8215 8216 8217 8218 8219 8220
      <dt><code>version</code></dt>
      <dd>
        <p>
          The <code>version</code> attribute indicates the version
          of the TPM. By default a TPM 1.2 is created. This attribute
          only works with the <code>emulator</code> backend. The following
          versions are supported:
        </p>
        <ul>
          <li>'1.2' : creates a TPM 1.2</li>
          <li>'2.0' : creates a TPM 2.0</li>
        </ul>
      </dd>
8221 8222
    </dl>

8223
    <h4><a id="elementsNVRAM">NVRAM device</a></h4>
L
Li Zhang 已提交
8224 8225 8226 8227 8228 8229 8230 8231 8232 8233
    <p>
      nvram device is always added to pSeries guest on PPC64, and its address
      is allowed to be changed.  Element <code>nvram</code> (only valid for
      pSeries guest, <span class="since">since 1.0.5</span>) is provided to
      enable the address setting.
    </p>
    <p>
      Example: usage of NVRAM configuration
    </p>
<pre>
8234 8235 8236 8237 8238 8239 8240
...
&lt;devices&gt;
  &lt;nvram&gt;
    &lt;address type='spapr-vio' reg='0x3000'/&gt;
  &lt;/nvram&gt;
&lt;/devices&gt;
...
L
Li Zhang 已提交
8241 8242 8243 8244 8245 8246 8247 8248 8249 8250 8251 8252 8253 8254 8255 8256
</pre>
  <dl>
    <dt><code>spapr-vio</code></dt>
    <dd>
      <p>
        VIO device address type, only valid for PPC64.
      </p>
    </dd>
    <dt><code>reg</code></dt>
    <dd>
      <p>
        Device address
      </p>
    </dd>
  </dl>

8257
    <h4><a id="elementsPanic">panic device</a></h4>
H
Hu Tao 已提交
8258 8259 8260 8261 8262
    <p>
      panic device enables libvirt to receive panic notification from a QEMU
      guest.
      <span class="since">Since 1.2.1, QEMU and KVM only</span>
    </p>
8263
    <p>
8264 8265 8266 8267 8268 8269 8270 8271 8272
      This feature is always enabled for:
    </p>
    <ul>
      <li>pSeries guests, since it's implemented by the guest firmware</li>
      <li>S390 guests, since it's an integral part of the S390 architecture</li>
    </ul>
    <p>
      For the guest types listed above, libvirt automatically adds a
      <code>panic</code> element to the domain XML.
8273
    </p>
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    <p>
      Example: usage of panic configuration
    </p>
<pre>
8278 8279 8280 8281 8282 8283 8284 8285
...
&lt;devices&gt;
  &lt;panic model='hyperv'/&gt;
  &lt;panic model='isa'&gt;
    &lt;address type='isa' iobase='0x505'/&gt;
  &lt;/panic&gt;
&lt;/devices&gt;
...
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</pre>
  <dl>
8288 8289 8290 8291 8292 8293 8294 8295
    <dt><code>model</code></dt>
      <dd>
        <p>
          The optional <code>model</code> attribute specifies what type
          of panic device is provided. The panic model used when this attribute
          is missing depends on the hypervisor and guest arch.
        </p>
        <ul>
8296 8297 8298
          <li>'isa' - for ISA pvpanic device</li>
          <li>'pseries' - default and valid only for pSeries guests.</li>
          <li>'hyperv' - for Hyper-V crash CPU feature.
8299
            <span class="since">Since 1.3.0, QEMU and KVM only</span></li>
8300
          <li>'s390' - default for S390 guests.
8301
            <span class="since">Since 1.3.5</span></li>
8302 8303
        </ul>
      </dd>
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    <dt><code>address</code></dt>
    <dd>
      <p>
        address of panic. The default ioport is 0x505. Most users
8308
        don't need to specify an address, and doing so is forbidden
8309
        altogether for s390, pseries and hyperv models.
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      </p>
    </dd>
  </dl>

8314
  <h4><a id="elementsShmem">Shared memory device</a></h4>
8315 8316 8317 8318

    <p>
      A shared memory device allows to share a memory region between
      different virtual machines and the host.
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      <span class="since">Since 1.2.10, QEMU and KVM only</span>
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    </p>

<pre>
8323 8324 8325 8326 8327 8328 8329 8330 8331 8332 8333 8334 8335 8336
...
&lt;devices&gt;
  &lt;shmem name='my_shmem0'&gt;
    &lt;model type='ivshmem-plain'/&gt;
    &lt;size unit='M'&gt;4&lt;/size&gt;
  &lt;/shmem&gt;
  &lt;shmem name='shmem_server'&gt;
    &lt;model type='ivshmem-doorbell'/&gt;
    &lt;size unit='M'&gt;2&lt;/size&gt;
    &lt;server path='/tmp/socket-shmem'/&gt;
    &lt;msi vectors='32' ioeventfd='on'/&gt;
  &lt;/shmem&gt;
&lt;/devices&gt;
...
8337 8338 8339 8340 8341 8342
</pre>

  <dl>
    <dt><code>shmem</code></dt>
    <dd>
      The <code>shmem</code> element has one mandatory attribute,
8343 8344 8345
      <code>name</code> to identify the shared memory. This attribute cannot
      be directory specific to <code>.</code> or <code>..</code> as well as
      it cannot involve path separator <code>/</code>.
8346
    </dd>
8347 8348 8349 8350
    <dt><code>model</code></dt>
    <dd>
      Attribute <code>type</code> of the optional element <code>model</code>
      specifies the model of the underlying device providing the
8351 8352 8353 8354 8355
      <code>shmem</code> device.  The models currently supported are
      <code>ivshmem</code> (supports both server and server-less shmem, but is
      deprecated by newer QEMU in favour of the -plain and -doorbell variants),
      <code>ivshmem-plain</code> (only for server-less shmem) and
      <code>ivshmem-doorbell</code> (only for shmem with the server).
8356
    </dd>
8357 8358 8359 8360 8361 8362 8363 8364 8365
    <dt><code>size</code></dt>
    <dd>
      The optional <code>size</code> element specifies the size of the shared
      memory. This must be power of 2 and greater than or equal to 1 MiB.
    </dd>
    <dt><code>server</code></dt>
    <dd>
      The optional <code>server</code> element can be used to configure a server
      socket the device is supposed to connect to.  The optional
8366 8367
      <code>path</code> attribute specifies the absolute path to the unix socket
      and defaults to <code>/var/lib/libvirt/shmem/$shmem-$name-sock</code>.
8368 8369 8370 8371 8372 8373 8374 8375 8376 8377 8378 8379
    </dd>
    <dt><code>msi</code></dt>
    <dd>
      The optional <code>msi</code> element enables/disables (values "on"/"off",
      respectively) MSI interrupts. This option can currently be used only
      together with the <code>server</code> element. The <code>vectors</code>
      attribute can be used to specify the number of interrupt
      vectors. The <code>ioeventd</code> attribute enables/disables (values
      "on"/"off", respectively) ioeventfd.
    </dd>
  </dl>

8380
    <h4><a id="elementsMemory">Memory devices</a></h4>
8381 8382 8383 8384 8385 8386 8387 8388 8389 8390 8391 8392 8393 8394 8395 8396

    <p>
        In addition to the initial memory assigned to the guest, memory devices
        allow additional memory to be assigned to the guest in the form of
        memory modules.

        A memory device can be hot-plugged or hot-unplugged depending on the
        guests' memory resource needs.

        Some hypervisors may require NUMA configured for the guest.
    </p>

    <p>
      Example: usage of the memory devices
    </p>
<pre>
8397 8398
...
&lt;devices&gt;
8399
  &lt;memory model='dimm' access='private' discard='yes'&gt;
8400 8401 8402 8403 8404 8405 8406 8407 8408 8409 8410 8411 8412 8413 8414
    &lt;target&gt;
      &lt;size unit='KiB'&gt;524287&lt;/size&gt;
      &lt;node&gt;0&lt;/node&gt;
    &lt;/target&gt;
  &lt;/memory&gt;
  &lt;memory model='dimm'&gt;
    &lt;source&gt;
      &lt;pagesize unit='KiB'&gt;4096&lt;/pagesize&gt;
      &lt;nodemask&gt;1-3&lt;/nodemask&gt;
    &lt;/source&gt;
    &lt;target&gt;
      &lt;size unit='KiB'&gt;524287&lt;/size&gt;
      &lt;node&gt;1&lt;/node&gt;
    &lt;/target&gt;
  &lt;/memory&gt;
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  &lt;memory model='nvdimm'&gt;
    &lt;source&gt;
      &lt;path&gt;/tmp/nvdimm&lt;/path&gt;
8418
      &lt;alignsize unit='KiB'&gt;2048&lt;/alignsize&gt;
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    &lt;/source&gt;
    &lt;target&gt;
      &lt;size unit='KiB'&gt;524288&lt;/size&gt;
      &lt;node&gt;1&lt;/node&gt;
8423 8424 8425
      &lt;label&gt;
        &lt;size unit='KiB'&gt;128&lt;/size&gt;
      &lt;/label&gt;
8426
      &lt;readonly/&gt;
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Michal Privoznik 已提交
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    &lt;/target&gt;
  &lt;/memory&gt;
8429 8430 8431 8432 8433 8434 8435 8436 8437 8438 8439 8440 8441
  &lt;memory model='nvdimm'&gt;
    &lt;source&gt;
      &lt;path&gt;/dev/dax0.0&lt;/path&gt;
      &lt;pmem/&gt;
    &lt;/source&gt;
    &lt;target&gt;
      &lt;size unit='KiB'&gt;524288&lt;/size&gt;
      &lt;node&gt;1&lt;/node&gt;
      &lt;label&gt;
        &lt;size unit='KiB'&gt;128&lt;/size&gt;
      &lt;/label&gt;
    &lt;/target&gt;
  &lt;/memory&gt;
8442 8443
&lt;/devices&gt;
...
8444 8445 8446 8447 8448
</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
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          Provide <code>dimm</code> to add a virtual DIMM module to the guest.
          <span class="since">Since 1.2.14</span>
          Provide <code>nvdimm</code> model adds a Non-Volatile DIMM
          module. <span class="since">Since 3.2.0</span>
8453 8454 8455
        </p>
      </dd>

8456 8457 8458 8459 8460 8461 8462 8463 8464 8465 8466 8467
      <dt><code>access</code></dt>
      <dd>
        <p>
          An optional attribute <code>access</code>
          (<span class="since">since 3.2.0</span>) that provides
          capability to fine tune mapping of the memory on per
          module basis. Values are the same as
          <a href="#elementsMemoryBacking">Memory Backing</a>:
          <code>shared</code> and <code>private</code>.
        </p>
      </dd>

8468 8469 8470 8471 8472 8473 8474 8475 8476 8477 8478 8479 8480 8481
      <dt><code>discard</code></dt>
      <dd>
        <p>
          An optional attribute <code>discard</code>
          (<span class="since">since 4.4.0</span>) that provides
          capability to fine tune discard of data on per module
          basis. Accepted values are <code>yes</code> and
          <code>no</code>. The feature is described here:
          <a href="#elementsMemoryBacking">Memory Backing</a>.
          This attribute is allowed only for
          <code>model='dimm'</code>.
        </p>
      </dd>

8482 8483 8484
      <dt><code>source</code></dt>
      <dd>
        <p>
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8485 8486 8487 8488 8489
          For model <code>dimm</code> this element is optional and allows to
          fine tune the source of the memory used for the given memory device.
          If the element is not provided defaults configured via
          <code>numatune</code> are used. If <code>dimm</code> is provided,
          then the following optional elements can be provided as well:
8490 8491
        </p>

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        <dl>
          <dt><code>pagesize</code></dt>
          <dd>
            <p>
              This element can be used to override the default
              host page size used for backing the memory device.
              The configured value must correspond to a page size
              supported by the host.
            </p>
          </dd>

          <dt><code>nodemask</code></dt>
          <dd>
            <p>
              This element can be used to override the default
              set of NUMA nodes where the memory would be
              allocated.
            </p>
          </dd>
        </dl>

8513
        <p>
8514 8515 8516 8517
          For model <code>nvdimm</code> this element is mandatory. The
          mandatory child element <code>path</code> represents a path in
          the host that backs the nvdimm module in the guest. The following
          optional elements may be used:
8518
        </p>
8519 8520 8521 8522 8523 8524 8525 8526 8527 8528 8529 8530 8531

        <dl>
          <dt><code>alignsize</code></dt>
          <dd>
            <p>
              The <code>alignsize</code> element defines the page size
              alignment used to mmap the address range for the backend
              <code>path</code>. If not supplied the host page size is used.
              For example, to mmap a real NVDIMM device a 2M-aligned page may
              be required.
              <span class="since">Since 5.0.0</span>
            </p>
          </dd>
8532 8533 8534 8535 8536 8537 8538 8539 8540 8541 8542

          <dt><code>pmem</code></dt>
          <dd>
            <p>
              If persistent memory is supported and enabled by the hypervisor
              in order to guarantee the persistence of writes to the vNVDIMM
              backend, then use the <code>pmem</code> element in order to
              utilize the feature.
              <span class="since">Since 5.0.0</span>
            </p>
          </dd>
8543
        </dl>
8544 8545 8546 8547 8548 8549 8550 8551 8552 8553 8554 8555 8556
      </dd>

      <dt><code>target</code></dt>
      <dd>
        <p>
          The mandatory <code>target</code> element configures the placement and
          sizing of the added memory from the perspective of the guest.
        </p>
        <p>
          The mandatory <code>size</code> subelement configures the size of the
          added memory as a scaled integer.
        </p>
        <p>
8557 8558 8559
          The <code>node</code> subelement configures the guest NUMA node to
          attach the memory to. The element shall be used only if the guest has
          NUMA nodes configured.
8560
        </p>
8561
        <p>
8562
          The following optional elements may be used:
8563
        </p>
8564 8565 8566 8567 8568 8569 8570 8571 8572 8573 8574 8575 8576 8577 8578 8579 8580 8581 8582 8583 8584 8585 8586 8587 8588 8589 8590 8591 8592 8593 8594

        <dl>
          <dt><code>label</code></dt>
          <dd>
            <p>
              For NVDIMM type devices one can optionally use
              <code>label</code> and its subelement <code>size</code>
              to configure the size of namespaces label storage
              within the NVDIMM module. The <code>size</code> element
              has usual meaning described
              <a href="#elementsMemoryAllocation">here</a>.
              For QEMU domains the following restrictions apply:
            </p>
            <ol>
              <li>the minimum label size is 128KiB,</li>
              <li>the remaining size (total-size - label-size) will be aligned
                to 4KiB as default.</li>
            </ol>
          </dd>

          <dt><code>readonly</code></dt>
          <dd>
            <p>
              The <code>readonly</code> element is used to mark the vNVDIMM
              as read-only. Only the real NVDIMM device backend can guarantee
              the guest write persistence, so other backend types should use
              the <code>readonly</code> element.
              <span class="since">Since 5.0.0</span>
            </p>
          </dd>
        </dl>
8595 8596 8597
      </dd>
    </dl>

8598
    <h4><a id="elementsIommu">IOMMU devices</a></h4>
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    <p>
      The <code>iommu</code> element can be used to add an IOMMU device.
      <span class="since">Since 2.1.0</span>
    </p>

    <p>
      Example:
    </p>
<pre>
8609 8610
...
&lt;devices&gt;
8611 8612 8613
  &lt;iommu model='intel'&gt;
    &lt;driver intremap='on'/&gt;
  &lt;/iommu&gt;
8614 8615
&lt;/devices&gt;
...
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8616 8617 8618 8619 8620 8621 8622 8623
</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          Currently only the <code>intel</code> model is supported.
        </p>
      </dd>
8624 8625 8626 8627 8628 8629 8630 8631 8632 8633 8634 8635 8636 8637 8638 8639 8640 8641
      <dt><code>driver</code></dt>
      <dd>
        <p>
          The <code>driver</code> subelement can be used to configure
          additional options:
        </p>
        <dl>
          <dt><code>intremap</code></dt>
          <dd>
            <p>
              The <code>intremap</code> attribute with possible values
              <code>on</code> and <code>off</code> can be used to
              turn on interrupt remapping, a part of the VT-d functionality.
              Currently this requires split I/O APIC
              (<code>&lt;ioapic driver='qemu'/&gt;</code>).
              <span class="since">Since 3.4.0</span> (QEMU/KVM only)
            </p>
          </dd>
8642 8643 8644 8645 8646 8647 8648 8649 8650
          <dt><code>caching_mode</code></dt>
          <dd>
            <p>
              The <code>caching_mode</code> attribute with possible values
              <code>on</code> and <code>off</code> can be used to
              turn on the VT-d caching mode (useful for assigned devices).
              <span class="since">Since 3.4.0</span> (QEMU/KVM only)
            </p>
          </dd>
8651 8652 8653 8654 8655 8656 8657 8658 8659 8660 8661 8662 8663
          <dt><code>eim</code></dt>
          <dd>
            <p>
              The <code>eim</code> attribute (with possible values
              <code>on</code> and <code>off</code>) can be used to
              configure Extended Interrupt Mode. A q35 domain with
              split I/O APIC (as described in
              <a href="#elementsFeatures">hypervisor features</a>),
              and both interrupt remapping and EIM turned on for
              the IOMMU, will be able to use more than 255 vCPUs.
              <span class="since">Since 3.4.0</span> (QEMU/KVM only)
            </p>
          </dd>
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          <dt><code>iotlb</code></dt>
          <dd>
            <p>
              The <code>iotlb</code> attribute with possible values
              <code>on</code> and <code>off</code> can be used to
              turn on the IOTLB used to cache address translation
              requests from devices.
              <span class="since">Since 3.5.0</span> (QEMU/KVM only)
            </p>
          </dd>
8674 8675
        </dl>
      </dd>
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8676 8677
    </dl>

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8678 8679 8680
    <h3><a id="vsock">Vsock</a></h3>

    <p>A vsock host/guest interface. The <code>model</code> attribute
8681 8682 8683 8684 8685
    defaults to <code>virtio</code>. <span class="since">Since 5.2.0</span>
    <code>model</code> can also be 'virtio-transitional' and
    'virtio-non-transitional', see
    <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
    for more details.
8686 8687
    The optional attribute <code>address</code> of the <code>cid</code>
    element specifies the CID assigned to the guest. If the attribute
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8688 8689 8690 8691 8692 8693 8694 8695
    <code>auto</code> is set to <code>yes</code>, libvirt
    will assign a free CID automatically on domain startup.
    <span class="since">Since 4.4.0</span></p>

<pre>
...
&lt;devices&gt;
  &lt;vsock model='virtio'&gt;
8696
    &lt;cid auto='no' address='3'/&gt;
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  &lt;/vsock&gt;
&lt;/devices&gt;
...</pre>


8702
    <h3><a id="seclabel">Security label</a></h3>
8703 8704 8705

    <p>
      The <code>seclabel</code> element allows control over the
8706 8707 8708 8709 8710
      operation of the security drivers. There are three basic
      modes of operation, 'dynamic' where libvirt automatically
      generates a unique security label, 'static' where the
      application/administrator chooses the labels, or 'none'
      where confinement is disabled. With dynamic
8711 8712 8713 8714 8715
      label generation, libvirt will always automatically
      relabel any resources associated with the virtual machine.
      With static label assignment, by default, the administrator
      or application must ensure labels are set correctly on any
      resources, however, automatic relabeling can be enabled
8716 8717
      if desired.  <span class="since">'dynamic' since 0.6.1, 'static'
      since 0.6.2, and 'none' since 0.9.10.</span>
8718 8719
    </p>

8720 8721 8722 8723 8724 8725 8726
    <p>
      If more than one security driver is used by libvirt, multiple
      <code>seclabel</code> tags can be used, one for each driver and
      the security driver referenced by each tag can be defined using
      the attribute <code>model</code>
    </p>

8727
    <p>
8728
      Valid input XML configurations for the top-level security label
8729 8730 8731 8732
      are:
    </p>

    <pre>
8733
&lt;seclabel type='dynamic' model='selinux'/&gt;
8734

8735 8736 8737
&lt;seclabel type='dynamic' model='selinux'&gt;
  &lt;baselabel&gt;system_u:system_r:my_svirt_t:s0&lt;/baselabel&gt;
&lt;/seclabel&gt;
8738

8739 8740 8741
&lt;seclabel type='static' model='selinux' relabel='no'&gt;
  &lt;label&gt;system_u:system_r:svirt_t:s0:c392,c662&lt;/label&gt;
&lt;/seclabel&gt;
8742

8743 8744 8745
&lt;seclabel type='static' model='selinux' relabel='yes'&gt;
  &lt;label&gt;system_u:system_r:svirt_t:s0:c392,c662&lt;/label&gt;
&lt;/seclabel&gt;
8746

8747
&lt;seclabel type='none'/&gt;
8748 8749
    </pre>

8750 8751 8752 8753 8754 8755 8756
    <p>
      If no 'type' attribute is provided in the input XML, then
      the security driver default setting will be used, which
      may be either 'none' or 'dynamic'. If a 'baselabel' is set
      but no 'type' is set, then the type is presumed to be 'dynamic'
    </p>

8757 8758 8759 8760 8761 8762 8763 8764 8765
    <p>
      When viewing the XML for a running guest with automatic
      resource relabeling active, an additional XML element,
      <code>imagelabel</code>, will be included. This is an
      output-only element, so will be ignored in user supplied
      XML documents
    </p>
    <dl>
      <dt><code>type</code></dt>
8766 8767 8768
      <dd>Either <code>static</code>, <code>dynamic</code> or <code>none</code>
        to determine whether libvirt automatically generates a unique security
        label or not.
8769 8770 8771 8772 8773 8774 8775 8776 8777 8778 8779 8780 8781
      </dd>
      <dt><code>model</code></dt>
      <dd>A valid security model name, matching the currently
        activated security model
      </dd>
      <dt><code>relabel</code></dt>
      <dd>Either <code>yes</code> or <code>no</code>. This must always
        be <code>yes</code> if dynamic label assignment is used. With
        static label assignment it will default to <code>no</code>.
      </dd>
      <dt><code>label</code></dt>
      <dd>If static labelling is used, this must specify the full
        security label to assign to the virtual domain. The format
8782 8783 8784 8785 8786 8787 8788 8789 8790 8791 8792
        of the content depends on the security driver in use:
        <ul>
          <li>SELinux: a SELinux context.</li>
          <li>AppArmor: an AppArmor profile.</li>
          <li>
            DAC: owner and group separated by colon. They can be
            defined both as user/group names or uid/gid. The driver will first
            try to parse these values as names, but a leading plus sign can
            used to force the driver to parse them as uid or gid.
          </li>
        </ul>
8793 8794 8795
      </dd>
      <dt><code>baselabel</code></dt>
      <dd>If dynamic labelling is used, this can optionally be
8796 8797 8798 8799 8800 8801 8802 8803 8804 8805
        used to specify the base security label that will be used to generate
        the actual label. The format of the content depends on the security
        driver in use.

        The SELinux driver uses only the <code>type</code> field of the
        baselabel in the generated label. Other fields are inherited from
        the parent process when using SELinux baselabels.

        (The example above demonstrates the use of <code>my_svirt_t</code>
        as the value for the <code>type</code> field.)
8806 8807 8808 8809 8810 8811 8812 8813
      </dd>
      <dt><code>imagelabel</code></dt>
      <dd>This is an output only element, which shows the
        security label used on resources associated with the virtual domain.
        The format of the content depends on the security driver in use
      </dd>
    </dl>

8814 8815 8816 8817 8818 8819 8820 8821 8822 8823
    <p>When relabeling is in effect, it is also possible to fine-tune
      the labeling done for specific source file names, by either
      disabling the labeling (useful if the file lives on NFS or other
      file system that lacks security labeling) or requesting an
      alternate label (useful when a management application creates a
      special label to allow sharing of some, but not all, resources
      between domains), <span class="since">since 0.9.9</span>.  When
      a <code>seclabel</code> element is attached to a specific path
      rather than the top-level domain assignment, only the
      attribute <code>relabel</code> or the
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      sub-element <code>label</code> are supported.  Additionally,
      <span class="since">since 1.1.2</span>, an output-only
      element <code>labelskip</code> will be present for active
      domains on disks where labeling was skipped due to the image
      being on a file system that lacks security labeling.
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    </p>

8831
    <h3><a id="keywrap">Key Wrap</a></h3>
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       <p>The content of the optional <code>keywrap</code> element specifies
        whether the guest will be allowed to perform the S390 cryptographic key
        management operations. A clear key can be protected by encrypting it
        under a unique wrapping key that is generated for each guest VM running
        on the host. Two variations of wrapping keys are generated: one version
        for encrypting protected keys using the DEA/TDEA algorithm, and another
        version for keys encrypted using the AES algorithm. If a
        <code>keywrap</code> element is not included, the guest will be granted
        access to both AES and DEA/TDEA key wrapping by default.</p>

        <pre>
&lt;domain&gt;
  ...
  &lt;keywrap&gt;
    &lt;cipher name='aes' state='off'/&gt;
  &lt;/keywrap&gt;
  ...
&lt;/domain&gt;
</pre>
    <p>
      At least one <code>cipher</code> element must be nested within the
      <code>keywrap</code> element.
    </p>
    <dl>
      <dt><code>cipher</code></dt>
      <dd>The <code>name</code> attribute identifies the algorithm
        for encrypting a protected key. The values supported for this attribute
        are <code>aes</code> for encryption under the AES wrapping key, or
        <code>dea</code> for encryption under the DEA/TDEA wrapping key. The
        <code>state</code> attribute indicates whether the cryptographic key
        management operations should be turned on for the specified encryption
        algorithm. The value can be set to <code>on</code> or <code>off</code>.
      </dd>
    </dl>

    <p>Note: DEA/TDEA is synonymous with DES/TDES.</p>

8870
    <h3><a id="sev">Launch Security</a></h3>
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    <p>
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       The contents of the <code>&lt;launchSecurity type='sev'&gt;</code> element
8874
       is used to provide the guest owners input used for creating an encrypted
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       VM using the AMD SEV feature (Secure Encrypted Virtualization).
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       SEV is an extension to the AMD-V architecture which supports running
       encrypted virtual machine (VMs) under the control of KVM. Encrypted
       VMs have their pages (code and data) secured such that only the guest
       itself has access to the unencrypted version. Each encrypted VM is
       associated with a unique encryption key; if its data is accessed to a
       different entity using a different key the encrypted guests data will
       be incorrectly decrypted, leading to unintelligible data.

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       For more information see various input parameters and its format see the
       <a href="https://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf">SEV API spec</a>
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       <span class="since">Since 4.4.0</span>
       </p>
    <pre>
&lt;domain&gt;
  ...
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  &lt;launchSecurity type='sev'&gt;
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    &lt;policy&gt;0x0001&lt;/policy&gt;
    &lt;cbitpos&gt;47&lt;/cbitpos&gt;
    &lt;reducedPhysBits&gt;1&lt;/reducedPhysBits&gt;
    &lt;dhCert&gt;RBBBSDDD=FDDCCCDDDG&lt;/dhCert&gt;
    &lt;session&gt;AAACCCDD=FFFCCCDSDS&lt;/session&gt;
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  &lt;/launchSecurity&gt;
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  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>cbitpos</code></dt>
      <dd>The required <code>cbitpos</code> element provides the C-bit (aka encryption bit)
      location in guest page table entry. The value of <code>cbitpos</code> is
      hypervisor dependent and can be obtained through the <code>sev</code> element
      from the domain capabilities.
      </dd>
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      <dt><code>reducedPhysBits</code></dt>
      <dd>The required <code>reducedPhysBits</code> element provides the physical
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      address bit reducation. Similar to <code>cbitpos</code> the value of <code>
      reduced-phys-bit</code> is hypervisor dependent and can be obtained
      through the <code>sev</code> element from the domain capabilities.
      </dd>
      <dt><code>policy</code></dt>
      <dd>The required <code>policy</code> element provides the guest policy
      which must be maintained by the SEV firmware. This policy is enforced by
      the firmware and restricts what configuration and operational commands
      can be performed on this guest by the hypervisor. The guest policy
      provided during guest launch is bound to the guest and cannot be changed
      throughout the lifetime of the guest. The policy is also transmitted
      during snapshot and migration flows and enforced on the destination platform.

      The guest policy is a 4 unsigned byte with the fields shown in Table:

      <table class="top_table">
        <tr>
          <th> Bit(s) </th>
          <th> Description </th>
        </tr>
        <tr>
          <td> 0 </td>
          <td> Debugging of the guest is disallowed when set </td>
        </tr>
        <tr>
          <td> 1 </td>
          <td> Sharing keys with other guests is disallowed when set </td>
        </tr>
        <tr>
          <td> 2 </td>
          <td> SEV-ES is required when set</td>
        </tr>
        <tr>
          <td> 3 </td>
          <td> Sending the guest to another platform is disallowed when set</td>
        </tr>
        <tr>
          <td> 4 </td>
          <td> The guest must not be transmitted to another platform that is
               not in the domain when set. </td>
        </tr>
        <tr>
          <td> 5 </td>
          <td> The guest must not be transmitted to another platform that is
               not SEV capable when set. </td>
        </tr>
        <tr>
          <td> 6:15 </td>
          <td> reserved </td>
        </tr>
        <tr>
          <td> 16:32 </td>
          <td> The guest must not be transmitted to another platform with a
               lower firmware version. </td>
        </tr>
      </table>

      </dd>
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      <dt><code>dhCert</code></dt>
      <dd>The optional <code>dhCert</code> element provides the guest owners
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      base64 encoded Diffie-Hellman (DH) key. The key is used to negotiate a
      master secret key between the SEV firmware and guest owner. This master
      secret key is then used to establish a trusted channel between SEV
      firmware and guest owner.
      </dd>
      <dt><code>session</code></dt>
      <dd>The optional <code>session</code> element provides the guest owners
      base64 encoded session blob defined in the SEV API spec.

      See SEV spec LAUNCH_START section for the session blob format.
      </dd>
    </dl>

8985
    <h2><a id="examples">Example configs</a></h2>
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    <p>
      Example configurations for each driver are provide on the
      driver specific pages listed below
    </p>

    <ul>
      <li><a href="drvxen.html#xmlconfig">Xen examples</a></li>
      <li><a href="drvqemu.html#xmlconfig">QEMU/KVM examples</a></li>
    </ul>
  </body>
</html>