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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<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>


    <h2><a name="elements">Element and attribute overview</a></h2>

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


    <h3><a name="elementsMetadata">General metadata</a></h3>

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<pre>
&lt;domain type='xen' id='3'&gt;
  &lt;name&gt;fv0&lt;/name&gt;
  &lt;uuid&gt;4dea22b31d52d8f32516782e98ab3fa0&lt;/uuid&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>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 name="elementsOS">Operating system booting</a></h3>

    <p>
      There are a number of different ways to boot virtual machines
      each with their own pros and cons.
    </p>

    <h4><a name="elementsOSBIOS">BIOS bootloader</a></h4>

    <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,
        and <code>machine</code> referring to the machine
        type. The <a href="formatcaps.html">Capabilities XML</a>
        provides details on allowed values for
        these. <span class="since">Since 0.0.1</span></dd>
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      <dt><code>loader</code></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>

    <h4><a name="elementsOSBootloader">Host bootloader</a></h4>

    <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>

    <h4><a name="elementsOSKernel">Direct kernel boot</a></h4>

    <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 name="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>

    <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;
&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 name="elementsSysinfo">SMBIOS System Information</a></h3>

    <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;
&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>
        </dl>
      </dd>
    </dl>

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    <h3><a name="elementsCPUAllocation">CPU Allocation</a></h3>
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488
<pre>
489
&lt;domain&gt;
490
  ...
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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>
        The vcpus element allows to control state of individual vcpus.

        The <code>id</code> attribute specifies the vCPU id as used by libvirt
        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
        count as set by the <code>vcpu</code> element minus 1.

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

        <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
        <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
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        the order may be be duplicated accross 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
        during certain operations to assure valid configuration.
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        Note that hypervisors may create hotpluggable vcpus differently from
        boot vcpus thus special initialization may be necessary.

        Hypervisors may require that vcpus enabled on boot which are not
        hotpluggable are clustered at the beginning starting with ID 0. It may
        be also required that vcpu 0 is always present and non-hotpluggable.

        Note that providing state for individual cpus may be necessary to enable
        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>

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    <h3><a name="elementsIOThreadsAllocation">IOThreads Allocation</a></h3>
      <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>
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      </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>
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    <h3><a name="elementsCPUTuning">CPU Tuning</a></h3>

<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;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;
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    &lt;vcpusched vcpus='0-4,^3' scheduler='fifo' priority='1'/&gt;
    &lt;iothreadsched iothreads='2' scheduler='batch'/&gt;
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  &lt;/cputune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
679
      <dt><code>cputune</code></dt>
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      <dd>
         The optional <code>cputune</code> element provides details
         regarding the cpu tunable parameters for the domain.
         <span class="since">Since 0.9.0</span>
      </dd>
685
      <dt><code>vcpupin</code></dt>
686
      <dd>
687
        The optional <code>vcpupin</code> element specifies which of host's
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        physical CPUs the domain VCPU will be pinned to. If this is omitted,
        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>
        specifies vcpu id, and the attribute <code>cpuset</code> is same as
        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
         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>
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      <dt><code>shares</code></dt>
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      <dd>
        The optional <code>shares</code> element specifies the proportional
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        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
        interval(unit: microseconds). Within <code>period</code>, each vcpu of
        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
        bandwidth(unit: microseconds). A domain with <code>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 quota with value 0 means no
        value. You can use this feature to ensure that all vcpus run at the same
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        speed.
        <span class="since">Only QEMU driver support since 0.9.4, LXC since
        0.9.10</span>
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      </dd>
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      <dt><code>emulator_period</code></dt>
      <dd>
        The optional <code>emulator_period</code> element specifies the enforcement
        interval(unit: microseconds). Within <code>emulator_period</code>, emulator
        threads(those excluding vcpus) of the domain will not be allowed to consume
        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
        allowed bandwidth(unit: microseconds) for domain's emulator threads(those
        excluding vcpus). A domain with <code>emulator_quota</code> as any negative
        value indicates that the domain has infinite bandwidth for emulator threads
        (those excluding vcpus), 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.
        <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
        enforcement interval(unit: microseconds) for IOThreads. Within
        <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
        allowed bandwidth(unit: microseconds) for IOThreads. A domain with
        <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
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        well (and is ignored for non-real-time ones). The value range
        for the priority depends on the host kernel (usually 1-99).
815
        <span class="since">Since 1.2.13</span>
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      </dd>

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    </dl>


    <h3><a name="elementsMemoryAllocation">Memory Allocation</a></h3>

<pre>
&lt;domain&gt;
  ...
826
  &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;
829 830 831 832 833 834
  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>memory</code></dt>
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      <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.

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

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        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>
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      </dd>

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      <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>


    <h3><a name="elementsMemoryBacking">Memory Backing</a></h3>

<pre>
&lt;domain&gt;
  ...
  &lt;memoryBacking&gt;
900 901 902
    &lt;hugepages&gt;
      &lt;page size="1" unit="G" nodeset="0-3,5"/&gt;
      &lt;page size="2" unit="M" nodeset="4"/&gt;
903
    &lt;/hugepages&gt;
904
    &lt;nosharepages/&gt;
905
    &lt;locked/&gt;
906 907 908 909 910
  &lt;/memoryBacking&gt;
  ...
&lt;/domain&gt;
</pre>

911 912 913 914
    <p>The optional <code>memoryBacking</code> element may contain several
      elements that influence how virtual memory pages are backed by host
      pages.</p>

915
    <dl>
916 917
      <dt><code>hugepages</code></dt>
      <dd>This tells the hypervisor that the guest should have its memory
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      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>
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      <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
937
        be allowed to swap them out. For QEMU/KVM this requires
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        <code>hard_limit</code> <a href="#elementsMemoryTuning">memory tuning</a>
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        element to be used and set to the maximum memory configured for the
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        domain plus any memory consumed by the QEMU process itself. Beware of
        setting the memory limit too high (and thus allowing the domain to lock
        most of the host's memory). Doing so may be dangerous to both the
        domain and the host itself since the host's kernel may run out of
        memory. <span class="since">Since 1.0.6</span></dd>
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    </dl>


    <h3><a name="elementsMemoryTuning">Memory Tuning</a></h3>

<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;
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  &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>
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        since 0.9.11</span>
        Possible values for all *_limit parameters are in range from 0 to
        VIR_DOMAIN_MEMORY_PARAM_UNLIMITED.</dd>
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      <dt><code>hard_limit</code></dt>
      <dd> The optional <code>hard_limit</code> element is the maximum memory
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        the guest can use. The units for this value are kibibytes (i.e. blocks
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        of 1024 bytes). <strong>However, users of QEMU and KVM are strongly
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        advised not to set this limit as domain may get killed by the kernel
        if the guess is too low. To determine the memory needed for a process
        to run is an
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        <a href="http://en.wikipedia.org/wiki/Undecidable_problem">
        undecidable problem</a>.</strong></dd>
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      <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
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        kibibytes (i.e. blocks of 1024 bytes)</dd>
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      <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
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        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
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        kibibytes (i.e. blocks of 1024 bytes). This element is only supported
        by VMware ESX and OpenVZ drivers.</dd>
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    </dl>


    <h3><a name="elementsNUMATuning">NUMA Node Tuning</a></h3>

<pre>
&lt;domain&gt;
  ...
  &lt;numatune&gt;
    &lt;memory mode="strict" nodeset="1-4,^3"/&gt;
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    &lt;memnode cellid="0" mode="strict" nodeset="1"/&gt;
    &lt;memnode cellid="2" mode="preferred" nodeset="2"/&gt;
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  &lt;/numatune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
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      <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>
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      <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.

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        <span class='since'>Since 0.9.3</span>
      </dd>
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      <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>

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    <h3><a name="elementsBlockTuning">Block I/O Tuning</a></h3>
<pre>
&lt;domain&gt;
  ...
  &lt;blkiotune&gt;
    &lt;weight&gt;800&lt;/weight&gt;
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    &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;
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      &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;
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    &lt;/device&gt;
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  &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
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        omitted, it defaults to the OS provided
        defaults. <span class="since">Since 0.8.8</span></dd>
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      <dt><code>weight</code></dt>
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      <dd> The optional <code>weight</code> element is the overall I/O
        weight of the guest. The value should be in the range [100,
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        1000]. After kernel 2.6.39, the value could be in the
        range [10, 1000].</dd>
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      <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>
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    <h3><a name="resPartition">Resource partitioning</a></h3>

    <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
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      element <code>partition</code> whose content defines the absolute path
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      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 name="elementsCPU">CPU model and topology</a></h3>

    <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;
  &lt;feature policy='disable' name='lahf_lm'/&gt;
&lt;/cpu&gt;
...</pre>
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<pre>
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&lt;cpu mode='host-model'&gt;
  &lt;model fallback='forbid'/&gt;
  &lt;topology sockets='1' cores='2' threads='1'/&gt;
&lt;/cpu&gt;
...</pre>
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<pre>
1191 1192 1193
&lt;cpu mode='host-passthrough'&gt;
  &lt;feature policy='disable' name='lahf_lm'/&gt;
...</pre>
1194

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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>
1202 1203 1204 1205 1206
...
&lt;cpu&gt;
  &lt;topology sockets='1' cores='2' threads='1'/&gt;
&lt;/cpu&gt;
...</pre>
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    <dl>
      <dt><code>cpu</code></dt>
      <dd>The <code>cpu</code> element is the main container for describing
        guest CPU requirements. Its <code>match</code> attribute specified how
        strictly has the virtual CPU provided to the guest match these
        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
            requested CPU.</dd>
          <dt><code>exact</code></dt>
          <dd>The virtual CPU provided to the guest will exactly match the
            specification</dd>
          <dt><code>strict</code></dt>
          <dd>The guest will not be created unless the host CPU does exactly
            match the specification.</dd>
        </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>.
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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. <strong>Beware</strong>, due to the
          way libvirt detects host CPU and due to the fact libvirt does not
          talk to QEMU/KVM when creating the CPU model, CPU configuration
          created using <code>host-model</code> may not work as expected. The
          guest CPU may differ from the configuration and it may also confuse
          guest OS by using a combination of CPU features and other parameters
          (such as CPUID level) that don't work. Until these issues are fixed,
          it's a good idea to avoid using <code>host-model</code> and use
          <code>custom</code> mode with just the CPU model from host
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          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
          <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>
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          </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>
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        </dl>

        In both <code>host-model</code> and <code>host-passthrough</code>
        mode, the real (approximate in <code>host-passthrough</code> mode) CPU
        definition which would be used on current host can be determined by
        specifying <code>VIR_DOMAIN_XML_UPDATE_CPU</code> flag when calling
        <code>virDomainGetXMLDesc</code> API. When running a guest that might
        be prone to operating system reactivation when presented with
        different hardware, and which will be migrated between hosts with
        different capabilities, you can use this output to rewrite XML to the
        <code>custom</code> mode for more robust migration.
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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
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        (<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
        socket, and number of threads per core, respectively.</dd>

      <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>
          <dd>Guest creation will fail unless the feature is supported by host
            CPU.</dd>
          <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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      </dd>
    </dl>

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    <p>
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      Guest NUMA topology can be specified using the <code>numa</code> element.
1377 1378 1379 1380
      <span class="since">Since 0.9.8</span>
    </p>

<pre>
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...
&lt;cpu&gt;
1383
  ...
1384 1385 1386 1387 1388 1389 1390
  &lt;numa&gt;
    &lt;cell id='0' cpus='0-3' memory='512000' unit='KiB'/&gt;
    &lt;cell id='1' cpus='4-7' memory='512000' unit='KiB' memAccess='shared'/&gt;
  &lt;/numa&gt;
  ...
&lt;/cpu&gt;
...</pre>
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    <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
      hugepages-backed memory.
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    </p>

    <p>
      This guest NUMA specification is currently available only for QEMU/KVM.
    </p>

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    <h3><a name="elementsEvents">Events configuration</a></h3>
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    <p>
A
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      It is sometimes necessary to override the default actions taken
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      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>.
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      Using <code>virsh reboot</code> or <code>virsh shutdown</code> would
      also trigger the event.
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    </p>

1437
<pre>
1438 1439 1440 1441 1442 1443
...
&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>
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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
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        released.</dd>
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      <dt><code>restart</code></dt>
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      <dd>The domain will be terminated and then restarted with
        the same configuration.</dd>
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      <dt><code>preserve</code></dt>
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      <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>
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      <dd>The domain will be terminated and then restarted with
        a new name.</dd>
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    </dl>

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    <p>
1484 1485 1486 1487 1488 1489 1490 1491 1492 1493
    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
1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506
      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>

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    <p>
      The <code>on_lockfailure</code> element (<span class="since">since
1509
      1.0.0</span>) may be used to configure what action should be
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      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>

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    <h3><a name="elementsPowerManagement">Power Management</a></h3>

    <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>
1537 1538 1539 1540 1541 1542
...
&lt;pm&gt;
  &lt;suspend-to-disk enabled='no'/&gt;
  &lt;suspend-to-mem enabled='yes'/&gt;
&lt;/pm&gt;
...</pre>
1543 1544 1545 1546

    <dl>
      <dt><code>pm</code></dt>
      <dd>These elements enable ('yes') or disable ('no') BIOS support
1547
        for S3 (suspend-to-mem) and S4 (suspend-to-disk) ACPI sleep
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        states. If nothing is specified, then the hypervisor will be
        left with its default value.</dd>
    </dl>

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    <h3><a name="elementsFeatures">Hypervisor features</a></h3>

    <p>
      Hypervisors may allow certain CPU / machine features to be
      toggled on/off.
    </p>

1559
<pre>
1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584
...
&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;
  &lt;/hyperv&gt;
  &lt;kvm&gt;
    &lt;hidden state='on'/&gt;
  &lt;/kvm&gt;
  &lt;pvspinlock state='on'/&gt;
  &lt;gic version='2'/&gt;

&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
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      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>
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      <dt><code>apic</code></dt>
      <dd>APIC allows the use of programmable IRQ
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      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
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      Interrupt) for the guest.
      </dd>
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      <dt><code>hap</code></dt>
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      <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>
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      <dt><code>viridian</code></dt>
      <dd>Enable Viridian hypervisor extensions for paravirtualizing
        guest operating systems
      </dd>
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      <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>
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      <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>
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          <th>Since</th>
1635 1636 1637
        </tr>
        <tr>
          <td>relaxed</td>
1638
          <td>Relax constraints on timers</td>
1639
          <td> on, off</td>
1640
          <td><span class="since">1.0.0 (QEMU 2.0)</span></td>
1641 1642 1643 1644 1645
        </tr>
        <tr>
          <td>vapic</td>
          <td>Enable virtual APIC</td>
          <td>on, off</td>
1646
          <td><span class="since">1.1.0 (QEMU 2.0)</span></td>
1647 1648 1649 1650 1651
        </tr>
        <tr>
          <td>spinlocks</td>
          <td>Enable spinlock support</td>
          <td>on, off; retries - at least 4095</td>
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          <td><span class="since">1.1.0 (QEMU 2.0)</span></td>
1653
        </tr>
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        <tr>
          <td>vpindex</td>
          <td>Virtual processor index</td>
          <td> on, off</td>
          <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>
          <td> on, off</td>
          <td><span class="since">1.3.3 (QEMU 2.5)</span></td>
        </tr>
        <tr>
          <td>synic</td>
          <td>Enable Synthetic Interrupt Controller (SyNIC)</td>
          <td> on, off</td>
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          <td><span class="since">1.3.3 (QEMU 2.6)</span></td>
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        </tr>
        <tr>
          <td>stimer</td>
          <td>Enable SyNIC timers</td>
          <td> on, off</td>
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          <td><span class="since">1.3.3 (QEMU 2.6)</span></td>
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        </tr>
        <tr>
          <td>reset</td>
          <td>Enable hypervisor reset</td>
          <td> on, off</td>
          <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>
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      </table>
      </dd>
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      <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>
1711
          <td><span class="since">1.2.8 (QEMU 2.1.0)</span></td>
1712 1713 1714
        </tr>
      </table>
      </dd>
1715 1716 1717 1718 1719 1720
      <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>
1721 1722 1723
      <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.
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        <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;
1733 1734 1735
          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>
      <dd>Enable System Management Mode. Possible values are
          <code>on</code> and <code>off</code>. The default is left
          for hypervisor to decide.
          <span class="since">Since 2.1.0</span>
      </dd>
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    </dl>

    <h3><a name="elementsTime">Time keeping</a></h3>

    <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>

1754
<pre>
1755 1756 1757 1758 1759 1760 1761 1762
...
&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>
1766
      <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
1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785
            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.
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            <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
1802 1803
            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
1806 1807 1808
            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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1809
            lost at each reboot. <span class="since">Since 0.7.7</span>
1810 1811
            <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
1816
          <code>timer</code> sub-elements. <span class="since">Since
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          0.8.0</span>
        </p>
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      </dd>
1820 1821
      <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
1832 1833 1834
            being modified, and can be one of
            "platform" (currently unsupported),
            "hpet" (libxl, xen, qemu), "kvmclock" (qemu),
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            "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>
1852 1853
            <p>
            The <code>tickpolicy</code> attribute determines what
1854
            happens when QEMU misses a deadline for injecting a
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            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>
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            <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>
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      </dd>
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    </dl>

1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924
    <h3><a name="elementsPerf">Performance monitoring events</a></h3>

    <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>
1925 1926 1927 1928 1929 1930 1931 1932 1933
...
&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;
1934
  &lt;event name='branch_instructions' enabled='no'/&gt;
1935
  &lt;event name='branch_misses' enabled='no'/&gt;
1936
  &lt;event name='bus_cycles' enabled='no'/&gt;
1937
  &lt;event name='stalled_cycles_frontend' enabled='no'/&gt;
1938
  &lt;event name='stalled_cycles_backend' enabled='no'/&gt;
1939
  &lt;event name='ref_cpu_cycles' enabled='no'/&gt;
1940 1941
&lt;/perf&gt;
...
1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964
</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>
1967
      <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>
1985 1986 1987 1988 1989
    <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>
1990 1991 1992 1993 1994
    <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>
1995 1996 1997 1998 1999
    <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>
2000 2001 2002 2003 2004 2005
    <tr>
      <td><code>stalled_cycles_frontend</code></td>
      <td>the count of stalled cpu cycles in the frontend of the instruction
          processor pipeline by applications running on the platform</td>
      <td><code>perf.stalled_cycles_frontend</code></td>
    </tr>
2006 2007 2008 2009 2010 2011
    <tr>
      <td><code>stalled_cycles_backend</code></td>
      <td>the count of stalled cpu cycles in the backend of the instruction
          processor pipeline by applications running on the platform</td>
      <td><code>perf.stalled_cycles_backend</code></td>
    </tr>
2012 2013 2014 2015 2016 2017
    <tr>
      <td><code>ref_cpu_cycles</code></td>
      <td>the count of total cpu cycles not affected by CPU frequency scaling
         by applications running on the platform</td>
      <td><code>perf.ref_cpu_cycles</code></td>
    </tr>
2018 2019
  </table>

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    <h3><a name="elementsDevices">Devices</a></h3>

    <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>

2029
<pre>
2030 2031 2032 2033 2034
...
&lt;devices&gt;
  &lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&gt;
&lt;/devices&gt;
...</pre>
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    <dl>
      <dt><code>emulator</code></dt>
      <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>

    <h4><a name="elementsDisks">Hard drives, floppy disks, CDROMs</a></h4>

    <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>

2055
<pre>
2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070
...
&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;
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      ...
2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209
    &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;
    &lt;/source&gt;
    &lt;target dev="hdc" bus="ide"/&gt;
    &lt;auth username='myuser'&gt;
      &lt;secret type='ceph' usage='mypassid'/&gt;
    &lt;/auth&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;
    &lt;source dev='/dev/sda'/&gt;
    &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;
    &lt;/source&gt;
    &lt;auth username='myuser'&gt;
      &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
    &lt;/auth&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;
    &lt;/source&gt;
    &lt;auth username='myuser'&gt;
      &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
    &lt;/auth&gt;
    &lt;target dev='sdb' bus='scsi'/&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:0:0:1' mode='host'/&gt;
    &lt;auth username='myuser'&gt;
      &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
    &lt;/auth&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;auth username='myuser'&gt;
      &lt;secret type='iscsi' usage='libvirtiscsi'/&gt;
    &lt;/auth&gt;
    &lt;target dev='vdc' bus='virtio'/&gt;
  &lt;/disk&gt;
  &lt;disk type='file' device='disk'&gt;
    &lt;driver name='qemu' type='qcow2'/&gt;
    &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;
2210
      &lt;/backingStore&gt;
2211 2212 2213 2214 2215
    &lt;/backingStore&gt;
    &lt;target dev='vdd' bus='virtio'/&gt;
  &lt;/disk&gt;
&lt;/devices&gt;
...</pre>
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    <dl>
      <dt><code>disk</code></dt>
2219 2220
      <dd>The <code>disk</code> element is the main container for
      describing disks and supports the following attributes:
2221
        <dl>
2222
          <dt><code>type</code></dt>
2223 2224 2225 2226 2227 2228
            <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.
2229
            <span class="since">Since 0.0.3</span>
2230
            </dd>
2231
          <dt><code>device</code></dt>
2232 2233 2234 2235 2236 2237
            <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
2238 2239
            valid when the <code>type</code> is "block" or "network" for
            <code>protocol='iscsi'</code> or when the <code>type</code>
2240
            is "volume" when using an iSCSI source <code>pool</code>
2241 2242 2243
            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.
2244
            Configured in this manner, the LUN behaves identically to "disk",
2245 2246 2247 2248 2249 2250
            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').
2251
            <span class="since">Since 0.1.4</span>
2252 2253
            </p>
            </dd>
2254
          <dt><code>rawio</code></dt>
2255
            <dd>
2256
            Indicates whether the disk needs rawio capability. Valid
2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267
            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>.
2268
            <span class="since">Since 0.9.10</span>
2269
            </dd>
2270
          <dt><code>sgio</code></dt>
2271
            <dd>
2272 2273 2274 2275
            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'.
2276
            <span class="since">Since 1.0.2</span>
2277
            </dd>
2278
          <dt><code>snapshot</code></dt>
2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291
            <dd>
            Indicates the default behavior of the disk during disk snapshots:
            "internal" requires a file format such as qcow2 that can store
            both the snapshot and the data changes since the snapshot;
            "external" will separate the snapshot from the live data; and
            "no" means the disk will not participate in snapshots. Read-only
            disks default to "no", while the default for other disks depends
            on the hypervisor's capabilities.  Some hypervisors allow a
            per-snapshot choice as well, during
            <a href="formatsnapshot.html">domain snapshot creation</a>.
            Not all snapshot modes are supported; for example,
            <code>snapshot='yes'</code> with a transient disk generally
            does not make sense.
2292
            <span class="since">Since 0.9.5</span>
2293 2294 2295
            </dd>
        </dl>
      </dd>
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      <dt><code>source</code></dt>
2297 2298 2299
      <dd>Representation of the disk <code>source</code> depends on the
      disk <code>type</code> attribute value as follows:
          <dl>
2300
            <dt><code>file</code></dt>
2301 2302 2303
              <dd>
              The <code>file</code> attribute specifies the fully-qualified
              path to the file holding the disk.
2304
              <span class="since">Since 0.0.3</span>
2305
              </dd>
2306
            <dt><code>block</code></dt>
2307
              <dd>
2308 2309
              The <code>dev</code> attribute specifies the fully-qualified path
              to the host device to serve as the disk.
2310
              <span class="since">Since 0.0.3</span>
2311
              </dd>
2312
            <dt><code>dir</code></dt>
2313 2314 2315
              <dd>
              The <code>dir</code> attribute specifies the fully-qualified path
              to the directory to use as the disk.
2316
              <span class="since">Since 0.7.5</span>
2317
              </dd>
2318
            <dt><code>network</code></dt>
2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331
              <dd>
              The <code>protocol</code> attribute specifies the protocol to
              access to the requested image. Possible values are "nbd",
              "iscsi", "rbd", "sheepdog" or "gluster".  If the
              <code>protocol</code> attribute is "rbd", "sheepdog" or
              "gluster", an additional attribute <code>name</code> is
              mandatory to specify which volume/image will be used. For "nbd",
              the <code>name</code> attribute is optional. 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.,
              <code>iqn.2013-07.com.example:iscsi-pool/1</code>). If not
              specified, the default LUN is zero.
2332
              <span class="since">Since 0.8.7</span>
2333
              </dd>
2334
            <dt><code>volume</code></dt>
2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360
              <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').
2361 2362 2363

              Using a LUN from an iSCSI source pool provides the same
              features as a <code>disk</code> configured using
2364
              <code>type</code> 'block' or 'network' and <code>device</code>
2365
              of 'lun' with respect to how the LUN is presented to and
2366
              may be used by the guest.
2367

2368
              <span class="since">Since 1.0.5</span>
2369 2370 2371 2372
              </p>
              </dd>
          </dl>
        With "file", "block", and "volume", one or more optional
2373
        sub-elements <code>seclabel</code>, <a href="#seclabel">described
2374 2375
        below</a> (and <span class="since">since 0.9.9</span>), can be
        used to override the domain security labeling policy for just
2376 2377
        that source file. (NB, for "volume" type disk, <code>seclabel</code>
        is only valid when the specified storage volume is of 'file' or
2378 2379
        'block' type).
        <p>
2380
        The <code>source</code> element may contain the following sub elements:
2381
        </p>
2382 2383 2384 2385 2386

        <dl>
          <dt><code>host</code></dt>
          <dd>
            <p>
2387 2388 2389 2390
            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.

2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419
            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>
2420
                <td> librados default </td>
2421 2422 2423 2424 2425 2426 2427 2428 2429 2430
              </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>
2431
                <td> one or more (<span class="since">Since 2.1.0</span>), just one prior to that </td>
2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442
                <td> 24007 </td>
              </tr>
            </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>
2443 2444 2445 2446 2447 2448 2449
          <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>
2450 2451 2452 2453 2454 2455 2456 2457
          <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>
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        </dl>

2460
        <p>
2461
        For a "file" or "volume" disk type which represents a cdrom or floppy
2462 2463
        (the <code>device</code> attribute), it is possible to define
        policy what to do with the disk if the source file is not accessible.
2464 2465
        (NB, <code>startupPolicy</code> is not valid for "volume" disk unless
         the specified storage volume is of "file" type). This is done by the
2466 2467
        <code>startupPolicy</code> attribute
        (<span class="since">since 0.9.7</span>),
2468
        accepting these values:
2469
        </p>
2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484
        <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>
2485 2486 2487 2488 2489 2490 2491
        <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>
2492
        </dd>
2493 2494
      <dt><code>backingStore</code></dt>
      <dd>
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        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
2509
        file correctly). The following attributes are
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        supported in <code>backingStore</code>:
2511
        <dl>
2512
          <dt><code>type</code></dt>
2513 2514 2515 2516 2517
          <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>
2518
          <dt><code>index</code></dt>
2519 2520 2521 2522 2523 2524 2525 2526
          <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>
2527 2528 2529 2530
        </dl>
        Moreover, <code>backingStore</code> supports the following sub-elements:
        <dl>
          <dt><code>format</code></dt>
2531 2532 2533 2534 2535
          <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>
2536
          <dt><code>source</code></dt>
2537 2538 2539 2540 2541 2542
          <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>
2543
          <dt><code>backingStore</code></dt>
2544 2545 2546 2547 2548 2549 2550
          <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>
2551 2552
      <dt><code>mirror</code></dt>
      <dd>
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        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
2566 2567 2568 2569 2570 2571
        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
2572
        copying.  For now, this element only valid in output; it is
2573 2574 2575 2576 2577 2578 2579
        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.
2580
      </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
2590 2591
        "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
2594 2595 2596 2597
        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.
2598 2599 2600 2601
        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;
2602
        <code>tray</code> attribute since 0.9.11; "usb" attribute value since
2603 2604
        after 0.4.4; "sata" attribute value since 0.9.7; "removable" attribute
        value since 1.1.3</span>
2605
      </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>
2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662
          <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
2663 2664 2665 2666 2667
            size of I/O operations per second.
          <p>
            <span class="since">Throughput limits since 1.2.11 and QEMU 1.7</span>
          </p>
          </dd>
2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678
          <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>
2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712
          <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>
2714
      </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.
2719
        <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",
2734 2735 2736 2737 2738 2739 2740 2741 2742
            "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
2746 2747 2748 2749 2750 2751 2752
            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
            0.9.7</span> The default setting of error_policy is "report".
            There is also an
            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
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            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
            given, the read error policy will be left at its default,
            which is "report".
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          </li>
          <li>
            The optional <code>io</code> attribute controls specific
            policies on I/O; qemu guests support "threads" and
2765
            "native". <span class="since">Since 0.8.8</span>
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          </li>
2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780
          <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>
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          <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
2785
            number of interrupts and exits for the guest. The default
2786 2787 2788 2789 2790 2791 2792 2793
            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
2796
            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
            to discard (also known as "trim" or "unmap") requests are
            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>
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          <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.
2821
            <span class='since'>Since 2.0.0</span>
2822
          </li>
2823 2824 2825 2826
          <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>
2827 2828 2829 2830 2831
            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>
2832
          </li>
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        </ul>
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      </dd>
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      <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>
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      <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
        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>
      </dd>
2849 2850 2851 2852 2853
      <dt><code>encryption</code></dt>
      <dd>If present, specifies how the volume is encrypted.  See
        the <a href="formatstorageencryption.html">Storage Encryption</a> page
        for more information.
      </dd>
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      <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
2857
        attribute <code>device='cdrom'</code>.
2858
      </dd>
2859 2860 2861 2862 2863
      <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>
2864 2865 2866 2867 2868 2869 2870
      <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>
2871 2872
      <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>.
2875 2876 2877
          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'.
2878 2879
          <span class="since">Since 0.7.1</span>
      </dd>
O
Osier Yang 已提交
2880 2881 2882
      <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
2883 2884
        of 16 hexadecimal digits and must be unique (at least among
        disks of a single domain)
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        <span class='since'>Since 0.10.1</span>
      </dd>
2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898
      <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>,
2908 2909 2910 2911 2912
        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
2913 2914 2915
        <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.
2916 2917
      </dd>
      <dt><code>auth</code></dt>
2918 2919 2920 2921
      <dd>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
2922 2923 2924 2925 2926 2927 2928 2929
        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
2930 2931 2932 2933 2934
        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>
2935 2936
        attribute matching the key that was specified in the
        secret object.  <span class="since">libvirt 0.9.7</span>
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2937
      </dd>
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2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956
      <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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Viktor Mihajlovski 已提交
2957 2958
      <dt><code>blockio</code></dt>
      <dd>If present, the <code>blockio</code> element allows
2959 2960 2961 2962 2963 2964 2965 2966
        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.
2967
          </dd>
2968 2969 2970 2971 2972
          <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.
2973
          </dd>
2974 2975
        </dl>
      </dd>
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    </dl>

2978 2979 2980 2981 2982 2983 2984 2985
    <h4><a name="elementsFilesystems">Filesystems</a></h4>

    <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>
2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004
...
&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;
3005
  ...
3006 3007
&lt;/devices&gt;
...</pre>
3008 3009 3010 3011 3012 3013 3014 3015 3016

    <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>
3017
        <dt><code>mount</code></dt>
3018 3019 3020 3021
        <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>.
3022
        This is the default <code>type</code> if one is not specified.
3023 3024 3025 3026
        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
3027 3028 3029 3030 3031 3032
        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>.
3033
        </dd>
3034
        <dt><code>template</code></dt>
3035 3036 3037
        <dd>
        OpenVZ filesystem template. Only used by OpenVZ driver.
        </dd>
3038
        <dt><code>file</code></dt>
3039
        <dd>
3040 3041 3042
        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.
3043
        </dd>
3044
        <dt><code>block</code></dt>
3045
        <dd>
3046 3047 3048
        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>.
3049
        </dd>
3050
        <dt><code>ram</code></dt>
3051 3052 3053
        <dd>
          An in-memory filesystem, using memory from the host OS.
          The source element has a single attribute <code>usage</code>
3054 3055
          which gives the memory usage limit in KiB, unless units
          are specified by the <code>units</code> attribute. Only used
3056 3057
          by LXC driver.
          <span class="since"> (since 0.9.13)</span></dd>
3058
        <dt><code>bind</code></dt>
3059 3060 3061 3062
        <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>
3063 3064
        </dl>

3065
      The filesystem block has an optional attribute <code>accessmode</code>
3066 3067 3068 3069 3070 3071
      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>
3072
        <dt><code>passthrough</code></dt>
3073 3074
        <dd>
        The <code>source</code> is accessed with the permissions of the
3075
        user inside the guest. This is the default <code>accessmode</code> if
3076 3077 3078
        one is not specified.
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
        </dd>
3079
        <dt><code>mapped</code></dt>
3080 3081 3082 3083 3084
        <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>
3085
        <dt><code>squash</code></dt>
3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096
        <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>

      </dd>

3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107
      <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
3108 3109
            supports a type of "loop", with a format of "raw" or
            "nbd" with any format. QEMU supports a type of "path"
3110
            or "handle", but no formats. Virtuozzo driver supports
D
Dmitry Guryanov 已提交
3111
            a type of "ploop" with a format of "ploop".
3112 3113 3114 3115
          </li>
        </ul>
      </dd>

3116 3117 3118 3119 3120
      <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
3121
        be used with <code>type='mount'</code>. The <code>usage</code> attribute
3122 3123
        is used with <code>type='ram'</code> to set the memory limit in KiB,
        unless units are specified by the <code>units</code> attribute.
3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135
      </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>
3136
        Enables exporting filesystem as a readonly mount for guest, by
3137 3138
        default read-write access is given (currently only works for
        QEMU/KVM driver).
3139
      </dd>
3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153

      <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>
3154 3155
    </dl>

3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174
    <h4><a name="elementsAddress">Device Addresses</a></h4>

    <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
3175
      uses <code>type='drive'</code>, while
3176 3177 3178 3179 3180 3181 3182 3183
      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>
3184
      <dt><code>pci</code></dt>
3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196
      <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
3197 3198 3199 3200 3201 3202 3203
        have multiple functions used.<br/>
        <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).
3204
      </dd>
3205
      <dt><code>drive</code></dt>
3206 3207 3208
      <dd>Drive addresses have the following additional
        attributes: <code>controller</code> (a 2-digit controller
        number), <code>bus</code> (a 2-digit bus number),
3209
        <code>target</code> (a 2-digit target number),
3210 3211
        and <code>unit</code> (a 2-digit unit number on the bus).
      </dd>
3212
      <dt><code>virtio-serial</code></dt>
3213 3214 3215 3216 3217
      <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>
3218
      <dt><code>ccid</code></dt>
3219 3220 3221 3222
      <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>
3223
      </dd>
3224
      <dt><code>usb</code></dt>
3225 3226 3227 3228 3229
      <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>
3230
      <dt><code>spapr-vio</code></dt>
3231 3232 3233 3234 3235 3236 3237 3238
      <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>
3239
      </dd>
3240
      <dt><code>ccw</code></dt>
B
Boris Fiuczynski 已提交
3241
      <dd>S390 guests with a <code>machine</code> value of
3242 3243 3244 3245 3246 3247 3248
        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
3249 3250
        cssid=0xfe and ssid=0. Virtio-ccw devices must have their cssid
        set to 0xfe.
3251
        <span class="since">Since 1.0.4</span>
3252
      </dd>
3253 3254 3255 3256 3257
      <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.
3258 3259 3260 3261 3262 3263 3264
        <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>
3265
      </dd>
3266
      <dt><code>isa</code></dt>
H
Hu Tao 已提交
3267 3268 3269 3270
      <dd>ISA addresses have the following additional
        attributes: <code>iobase</code> and <code>irq</code>.
        <span class="since">Since 1.2.1</span>
      </dd>
3271 3272
    </dl>

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3273 3274 3275
    <h4><a name="elementsControllers">Controllers</a></h4>

    <p>
3276
      Depending on the guest architecture, some device buses can
3277 3278
      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
3279 3280 3281 3282 3283
      controllers without requiring explicit XML markup, but sometimes
      it is necessary to provide an explicit controller element.
    </p>

<pre>
3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294
...
&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
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3295
  ...
3296 3297
&lt;/devices&gt;
...</pre>
E
Eric Blake 已提交
3298 3299 3300

    <p>
      Each controller has a mandatory attribute <code>type</code>,
3301 3302
      which must be one of 'ide', 'fdc', 'scsi', 'sata', 'usb',
      'ccid', 'virtio-serial' or 'pci', and a mandatory
3303 3304
      attribute <code>index</code> which is the decimal integer
      describing in which order the bus controller is encountered (for
3305
      use in <code>controller</code> attributes of
3306 3307 3308 3309 3310
      <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:
3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327
    </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
        controller.</dd>
        <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",
3328 3329 3330
        "vt82c686b-uhci", "pci-ohci", "nec-xhci", "qusb1" (xen pvusb
        with qemu backend, version 1.1) or "qusb2" (xen pvusb with qemu
        backend, version 2.0). Additionally,
3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342
         <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>
      </dl>

    <p>
      Note: The PowerPC64 "spapr-vio" addresses do not have an
      associated controller.
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3343 3344 3345 3346 3347 3348
    </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
3349
      semantics <a href="#elementsAddress">given above</a>.
E
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3350 3351
    </p>

3352 3353
    <p>
      An optional sub-element <code>driver</code> can specify the driver
3354
      specific options:
3355
    </p>
3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378
    <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>
3379 3380 3381 3382 3383 3384 3385 3386
      <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>
3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403
      <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>
3404
    </dl>
3405 3406 3407 3408 3409 3410
    <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.
3411 3412 3413 3414 3415
      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>.
3416 3417 3418
    </p>

<pre>
3419 3420 3421 3422 3423 3424 3425 3426 3427
...
&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;
3428
  ...
3429 3430
&lt;/devices&gt;
...</pre>
J
Ján Tomko 已提交
3431 3432 3433

    <p>
      PCI controllers have an optional <code>model</code> attribute with
3434
      possible values <code>pci-root</code>, <code>pcie-root</code>,
3435
      <code>pcie-root-port</code>, <code>pci-bridge</code>,
3436
      <code>dmi-to-pci-bridge</code>, <code>pcie-switch-upstream-port</code>,
3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448
      <code>pcie-switch-downstream-port</code>, <code>pci-expander-bus</code>,
      or <code>pcie-expander-bus</code>.  (pci-root and
      pci-bridge <span class="since">since 1.0.5</span>, pcie-root and
      dmi-to-pci-bridge <span class="since">since 1.1.2</span>,
      pcie-root-port, pcie-switch-upstream-port,
      pcie-switch-downstream-port <span class="since">since
      1.2.19</span>, and pci-expander-bus and
      pcie-expander-bus <span class="since">since 1.3.4</span>) The
      root controllers (<code>pci-root</code>
      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
3449 3450 3451 3452 3453
      <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>
3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466
    <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>
3467 3468
    <p>
      PCI controllers also have an optional
3469 3470 3471
      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
3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487
      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
3488
        must be between 1 and 255.
3489
      </dd>
3490 3491
      <dt><code>chassis</code></dt>
      <dd>
3492 3493
        pcie-root-port and pcie-switch-downstream-port controllers can
        also have a <code>chassis</code> attribute in
3494 3495 3496 3497 3498 3499 3500
        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>
3501 3502 3503
        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
3504 3505 3506 3507
        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>
3508 3509
      <dt><code>busNr</code></dt>
      <dd>
3510
        pci-expander-bus and pcie-expander-bus controllers can have an
3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524
        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).
3525 3526 3527 3528 3529 3530 3531
        <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
3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542
          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
          numbers above it to accomodate giving out one bus number for
          the upstream-port and one for each downstream-port (in
          addition to the pcie-root-port and the pcie-expander-bus
          itself).
3543
        </p>
3544
      </dd>
3545
      <dt><code>node</code></dt>
3546 3547 3548 3549 3550 3551 3552 3553 3554 3555
      <dd>
        pci-expander-bus controllers can have an
        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>
3556
    </dl>
3557
    <p>
L
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3558
      For machine types which provide an implicit PCI bus, the pci-root
J
Ján Tomko 已提交
3559
      controller with index=0 is auto-added and required to use PCI devices.
L
Laine Stump 已提交
3560
      pci-root has no address.
3561 3562 3563
      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
3564 3565 3566 3567 3568 3569
      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>
3570 3571 3572 3573 3574 3575 3576 3577
...
&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
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3578 3579 3580 3581 3582 3583

    <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
3584 3585 3586 3587 3588 3589
      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
      hotplugged. In order to make standard PCI slots available on a
      system which has a pcie-root controller, a pci controller
3590
      with <code>model='dmi-to-pci-bridge'</code> is automatically
3591 3592 3593 3594
      added, usually at the defacto standard location of slot=0x1e. A
      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
3595 3596 3597
      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
3598
      controller; all guest PCI devices with addresses that are
3599 3600
      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
3601
    </p>
3602 3603
    <p>
      Domains with an implicit pcie-root can also add controllers
3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629
      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>)
3630
    </p>
L
Laine Stump 已提交
3631
<pre>
3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642
...
&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>
3643

3644 3645 3646 3647 3648 3649 3650 3651 3652
    <h4><a name="elementsLease">Device leases</a></h4>

    <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>
3653 3654
...
&lt;devices&gt;
3655
  ...
3656 3657 3658 3659 3660 3661 3662 3663
  &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>
3664 3665

    <dl>
3666
      <dt><code>lockspace</code></dt>
3667 3668 3669 3670
      <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>
3671
      <dt><code>key</code></dt>
3672 3673 3674 3675
      <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>
3676
      <dt><code>target</code></dt>
3677 3678 3679 3680 3681 3682
      <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
        require a offset, just pass 0.
      </dd>
    </dl>
E
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3683

3684 3685
    <h4><a name="elementsHostDev">Host device assignment</a></h4>

3686
    <h5><a name="elementsHostDevSubsys">USB / PCI / SCSI devices</a></h5>
3687 3688

    <p>
H
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3689
      USB, PCI and SCSI devices attached to the host can be passed through
3690
      to the guest using the <code>hostdev</code> element.
H
Han Cheng 已提交
3691 3692
      <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>:
3693 3694
    </p>

3695
<pre>
3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706
...
&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>
3707

3708
    <p>or:</p>
3709 3710

<pre>
3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721
...
&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
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3722 3723 3724 3725

    <p>or:</p>

<pre>
3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737
...
&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>
3738

J
John Ferlan 已提交
3739 3740 3741 3742

    <p>or:</p>

<pre>
3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755
...
&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
3756

3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767
    <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;
  ...</pre>

3768 3769 3770
    <dl>
      <dt><code>hostdev</code></dt>
      <dd>The <code>hostdev</code> element is the main container for describing
J
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3771 3772 3773 3774
        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>
3775
          <dt><code>usb</code></dt>
3776 3777 3778
          <dd>USB devices are detached from the host on guest startup
            and reattached after the guest exits or the device is
            hot-unplugged.
J
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3779
          </dd>
3780
          <dt><code>pci</code></dt>
J
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3781 3782 3783
          <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
3784 3785 3786 3787 3788 3789
            <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
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3790
          </dd>
3791
          <dt><code>scsi</code></dt>
J
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3792
          <dd>For SCSI devices, user is responsible to make sure the device
3793 3794 3795 3796 3797 3798
            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>
3799 3800 3801 3802 3803 3804
            (<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.
J
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3805
          </dd>
3806 3807 3808 3809 3810 3811
          <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
            the guest.
          </dd>
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        </dl>
3813 3814 3815 3816 3817 3818
        <p>
          Note: The <code>managed</code> attribute is only used with PCI devices
          and is ignored by all the other device types, thus setting
          <code>managed</code> explicitly with other than PCI device has the same
          effect as omitting it.
        </p>
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3819
      </dd>
3820
      <dt><code>source</code></dt>
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3821 3822 3823
      <dd>The source element describes the device as seen from the host using
        the following mechanism to describe:
        <dl>
3824
          <dt><code>usb</code></dt>
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          <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>
3852
          <dt><code>pci</code></dt>
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          <dd>PCI devices can only be described by their <code>address</code>.
          </dd>
3855
          <dt><code>scsi</code></dt>
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          <dd>SCSI devices are described by both the <code>adapter</code>
3857 3858 3859 3860 3861 3862 3863 3864
            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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            <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>
3875 3876 3877 3878 3879 3880 3881
          <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>
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        </dl>
3883
      </dd>
3884 3885 3886 3887 3888
      <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>
3889 3890 3891 3892 3893 3894
      <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.
3895 3896
      <span class="since">Since 0.8.8</span> for PCI devices,
      <span class="since">Since 1.0.1</span> for USB devices.
3897
      </dd>
3898 3899
      <dt><code>rom</code></dt>
      <dd>The <code>rom</code> element is used to change how a PCI
3900
        device's ROM is presented to the guest. The optional <code>bar</code>
3901 3902 3903 3904 3905 3906 3907
        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
3908
        0.9.7 (QEMU and KVM only)</span>. The optional
3909
        <code>file</code> attribute contains an absolute path to a binary file
3910 3911 3912 3913 3914
        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>.
3915
      </dd>
3916
      <dt><code>address</code></dt>
3917 3918 3919 3920 3921
      <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.
3922
      For PCI devices the element carries 4 attributes allowing to designate
3923
      the device as can be found with the <code>lspci</code> or
3924 3925
      with <code>virsh nodedev-list</code>. For SCSI devices a 'drive'
      address type must be used. <a href="#elementsAddress">See above</a> for
3926 3927 3928 3929 3930 3931 3932 3933
      more details on the address element.</dd>
      <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"
3934
        (the legacy device assignment handled directly by the KVM
3935
        kernel module)<span class="since">Since 1.0.5 (QEMU and KVM
3936 3937 3938 3939 3940 3941 3942 3943
        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").
3944
      </dd>
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      <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>
3949 3950 3951 3952 3953
      <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>
3954 3955 3956 3957 3958
        <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>
3959
      </dd>
3960 3961
    </dl>

3962

3963
    <h5><a name="elementsHostDevCaps">Block / character devices</a></h5>
3964 3965 3966 3967

    <p>
      Block / character devices from the host can be passed through
      to the guest using the <code>hostdev</code> element. This is
3968 3969
      only possible with container based virtualization. Devices are specified
      by a fully qualified path.
3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989
      <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;
3990 3991 3992
...
    </pre>

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    <pre>
3994 3995 3996 3997 3998 3999
...
&lt;hostdev mode='capabilities' type='net'&gt;
  &lt;source&gt;
    &lt;interface&gt;eth0&lt;/interface&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
4000 4001 4002 4003 4004 4005 4006
...
    </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
4007 4008
        always "capabilities" and <code>type</code> is "storage" for a block
        device, "misc" for a character device and "net" for a host network
4009
        interface.
4010 4011 4012 4013 4014
      </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
4015 4016
        devices the "char" element is used. For network interfaces, the
        name of the interface is provided in the "interface" element.
4017 4018 4019
      </dd>
    </dl>

4020 4021 4022 4023 4024 4025 4026 4027 4028
    <h4><a name="elementsRedir">Redirected devices</a></h4>

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

<pre>
4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040
...
&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>
4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054

    <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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        device</a>) are typical. The redirdev element has an optional
        sub-element <code>&lt;address&gt;</code> which can tie the
4057 4058 4059 4060
        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
4061 4062 4063 4064 4065 4066 4067 4068 4069 4070
        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>)
4071 4072 4073 4074
      </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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        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,
4077
        0x08 represents mass storage devices. The USB device can be addressed by
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        vendor / product id using the <code>vendor</code> and <code>product</code> attributes.
4079 4080
        <code>version</code> is the device revision from the bcdDevice field (not
        the version of the USB protocol).
4081
        These four attributes are optional and <code>-1</code> can be used to allow
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        any value for them. <code>allow</code> attribute is mandatory,
4083 4084
        'yes' means allow, 'no' for deny.
      </dd>
4085 4086
    </dl>

4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102
    <h4><a name="elementsSmartcard">Smartcard devices</a></h4>

    <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>
4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119
...
&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;
...
4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130
</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>
4131
      <dt><code>host</code></dt>
4132 4133 4134 4135 4136 4137
      <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>

4138
      <dt><code>host-certificates</code></dt>
4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151
      <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>

4152
      <dt><code>passthrough</code></dt>
4153 4154 4155 4156 4157 4158 4159
      <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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      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
4165 4166 4167 4168 4169 4170 4171 4172 4173
      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
4174 4175 4176
      correlation between the smartcard and a ccid bus
      controller, <a href="#elementsAddress">documented above</a>.
      For now, qemu only supports at most one
4177 4178 4179
      smartcard, with an address of bus=0 slot=0.
    </p>

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    <h4><a name="elementsNICS">Network interfaces</a></h4>

4182
<pre>
4183 4184 4185 4186 4187 4188 4189 4190 4191 4192
...
&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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    <p>
      There are several possibilities for specifying a network
      interface visible to the guest.  Each subsection below provides
4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208
      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
4210 4211 4212 4213
      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
4216 4217
      attribute <code>type='pci'</code>
      as <a href="#elementsAddress">documented above</a>.
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    </p>

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4220 4221 4222 4223 4224
    <h5><a name="elementsNICSVirtual">Virtual network</a></h5>

    <p>
      <strong><em>
      This is the recommended config for general guest connectivity on
4225 4226 4227 4228
      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>
4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259

      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
4260
      <a href="#elementsNICSTargetOverride">overriding the target element</a>).
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    </p>
4262 4263 4264 4265 4266 4267
    <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
4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286
      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.
4292 4293 4294
      (<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
G
Guannan Ren 已提交
4295
      an <code>profileid</code> (in case the switch is 802.1Qbh) and
4296 4297 4298 4299 4300 4301 4302 4303 4304
      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.
4305
    </p>
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4306

4307
<pre>
4308 4309 4310 4311 4312
...
&lt;devices&gt;
  &lt;interface type='network'&gt;
    &lt;source network='default'/&gt;
  &lt;/interface&gt;
4313
  ...
4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324
  &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>
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4326
    <h5><a name="elementsNICSBridge">Bridge to LAN</a></h5>
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4327 4328 4329 4330

    <p>
      <strong><em>
      This is the recommended config for general guest connectivity on
4331
      hosts with static wired networking configs.
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4332 4333 4334 4335
      </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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4337 4338 4339
      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
4340 4341 4342 4343 4344
      &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.
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4345
    </p>
4346 4347 4348
    <p>
      On Linux systems, the bridge device is normally a standard Linux
      host bridge. On hosts that support Open vSwitch, it is also
4349
      possible to connect to an Open vSwitch bridge device by adding
4350 4351 4352 4353 4354 4355
      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
Chen Hanxiao 已提交
4356
      you do not specify one, a random interfaceid will be generated
4357 4358 4359 4360
      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>
4361
<pre>
4362 4363
...
&lt;devices&gt;
4364
  ...
4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381
  &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>
4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395

    <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>
4396 4397
...
&lt;devices&gt;
4398
  ...
4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415
  &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>
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    <h5><a name="elementsNICSSlirp">Userspace SLIRP stack</a></h5>

    <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
      VMs to have outgoing access.
    </p>

4428
<pre>
4429 4430 4431
...
&lt;devices&gt;
  &lt;interface type='user'/&gt;
4432
  ...
4433 4434 4435 4436 4437
  &lt;interface type='user'&gt;
    &lt;mac address="00:11:22:33:44:55"/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
D
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4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451


    <h5><a name="elementsNICSEthernet">Generic ethernet connection</a></h5>

    <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>

4452
<pre>
4453 4454 4455
...
&lt;devices&gt;
  &lt;interface type='ethernet'/&gt;
4456
  ...
4457 4458 4459 4460 4461 4462
  &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>
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4463

4464 4465 4466 4467
    <h5><a name="elementsNICSDirect">Direct attachment to physical interface</a></h5>

    <p>
      Provides direct attachment of the virtual machine's NIC to the given
4468
      physical interface of the host.
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      <span class="since">Since 0.7.7 (QEMU and KVM only)</span><br/>
4470 4471 4472
      This setup requires the Linux macvtap
      driver to be available. <span class="since">(Since Linux 2.6.34.)</span>
      One of the modes 'vepa'
4473
      ( <a href="http://www.ieee802.org/1/files/public/docs2009/new-evb-congdon-vepa-modular-0709-v01.pdf">
4474
      'Virtual Ethernet Port Aggregator'</a>), 'bridge' or 'private'
4475
      can be chosen for the operation mode of the macvtap device, 'vepa'
4476 4477
      being the default mode. The individual modes cause the delivery of
      packets to behave as follows:
4478
    </p>
4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490
    <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>
4491

4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502
    <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
4503
      a VEPA capable bridge is required.</dd>
4504 4505 4506 4507 4508 4509
      <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>
4510 4511 4512 4513 4514 4515 4516
      <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>
4517 4518
    </dl>

4519
<pre>
4520 4521
...
&lt;devices&gt;
4522
  ...
4523 4524 4525 4526 4527
  &lt;interface type='direct' trustGuestRxFilters='no'&gt;
    &lt;source dev='eth0' mode='vepa'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
4528

4529 4530 4531 4532
    <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
Eric Blake 已提交
4533
    </p>
4534 4535 4536 4537 4538 4539 4540
    <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
4541
      of a virtual machine. <span class="since">Since 0.8.2</span>
4542
    </p>
4543 4544 4545 4546
    <p>
      Please note that IEEE 802.1Qbg requires a non-zero value for the
      VLAN ID.
    </p>
4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567
    <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>
4568 4569
...
&lt;devices&gt;
4570
  ...
4571 4572 4573 4574 4575 4576 4577 4578
  &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>
4579

4580 4581 4582 4583 4584 4585 4586 4587 4588
    <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
4589
        be applied to this interface.  This name is resolved by the port
4590 4591 4592 4593 4594
        profile database into the network parameters from the port profile,
        and those network parameters will be applied to this interface.
      </dd>
    </dl>
  <pre>
4595 4596
...
&lt;devices&gt;
4597
  ...
4598 4599 4600 4601 4602 4603 4604 4605 4606
  &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>
4607

4608 4609 4610 4611 4612 4613 4614 4615

    <h5><a name="elementsNICSHostdev">PCI Passthrough</a></h5>

    <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
4616
      an 802.1Qbh capable switch using an optionally specified
4617
      &lt;virtualport&gt; element (see the examples of virtualport
4618 4619 4620 4621 4622 4623 4624 4625 4626
      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>

4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638
    <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>

4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652
    <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>

4653 4654 4655 4656 4657 4658
    <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
John Ferlan 已提交
4659
      (or <code>virsh nodedev-detach</code>) before starting the guest
4660 4661 4662 4663 4664
      or hot-plugging the device, and <code>virNodeDeviceReAttach</code>
      (or <code>virsh nodedev-reattach</code>) after hot-unplug or
      stopping the guest.
    </p>

4665
<pre>
4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679
...
&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>
4680 4681


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4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695
    <h5><a name="elementsNICSMulticast">Multicast tunnel</a></h5>

    <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>

4696
<pre>
4697 4698 4699 4700 4701 4702 4703 4704
...
&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
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4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716

    <h5><a name="elementsNICSTCP">TCP tunnel</a></h5>

    <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>

4717
<pre>
4718 4719 4720 4721 4722 4723
...
&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;
4724
  ...
4725 4726 4727 4728 4729 4730
  &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>
4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744

    <h5><a name="elementsNICSUDP">UDP unicast tunnel</a></h5>

    <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>
4745 4746 4747 4748 4749 4750 4751 4752 4753 4754
...
&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>
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4755

4756 4757
    <h5><a name="elementsNICSModel">Setting the NIC model</a></h5>

4758
<pre>
4759 4760 4761 4762 4763 4764 4765 4766 4767
...
&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>
4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789

    <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:
      ne2k_isa i82551 i82557b i82559er ne2k_pci pcnet rtl8139 e1000 virtio
    </p>
D
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4790

4791 4792 4793
    <h5><a name="elementsDriverBackendOptions">Setting NIC driver-specific options</a></h5>

<pre>
4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807
...
&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;driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5' rx_queue_size='256'&gt;
      &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;
    </b>
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
4808 4809 4810 4811 4812 4813 4814 4815 4816

    <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>
4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828
      <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>
4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840
      <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>
4841 4842 4843 4844 4845
      <dd>
        For interfaces of type='vhostuser', the <code>name</code>
        attribute is ignored. The backend driver used is always
        vhost-user.
      </dd>
4846

4847 4848 4849 4850 4851
      <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
4852
        <span class="since">Since 0.8.8 (QEMU and KVM only)</span><br/><br/>
4853 4854 4855 4856

        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
4857
        option).<br/><br/>
4858 4859 4860 4861

        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
4862
        fires, another attempt is made to send more data.<br/><br/>
4863 4864 4865 4866 4867

        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
        contention since the cpu doing the tx isn't necessarily the
E
Eric Blake 已提交
4868
        cpu where the guest generated the packets."<br/><br/>
4869

4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885
        <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/>

4886
        <b>In general you should leave this option alone, unless you
4887 4888 4889 4890 4891 4892
        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'
4893
        - if it is on, it will reduce the number of interrupts and
4894 4895 4896 4897 4898 4899 4900
        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
4901 4902
        are very certain you know what you are doing.</b>
      </dd>
4903 4904
      <dt><code>queues</code></dt>
      <dd>
4905 4906 4907 4908 4909 4910 4911
        The optional <code>queues</code> attribute controls the number
        of queues to be used for either
        <a href="http://www.linux-kvm.org/page/Multiqueue"> Multiqueue
        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
4912
        processor, resulting in much higher throughput.
4913
        <span class="since">virtio-net since 1.0.6 (QEMU and KVM only)</span>
4914
        <span class="since">vhost-user since 1.2.17 (QEMU and KVM only)</span>
4915
      </dd>
4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929
      <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.
        <span class="since">Since 2.3.0 (QEMU and KVM only)</span><br/><br/>

        <b>In general you should leave this option alone, unless you
        are very certain you know what you are doing.</b>
      </dd>
4930 4931 4932 4933 4934 4935 4936
    </dl>
    <p>
      Offloading options for the host and guest can be configured using
      the following sub-elements:
    </p>
    <dl>
      <dt><code>host</code></dt>
4937 4938 4939 4940 4941 4942 4943
      <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>
4944 4945 4946 4947
        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>
4948
      </dd>
4949
      <dt><code>guest</code></dt>
4950 4951 4952 4953 4954 4955 4956 4957
      <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>
4958 4959
    </dl>

4960 4961 4962
    <h5><a name="elementsBackendOptions">Setting network backend-specific options</a></h5>

<pre>
4963 4964 4965 4966 4967 4968 4969 4970
...
&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
4971 4972 4973
    <b>&lt;tune&gt;
      &lt;sndbuf&gt;1600&lt;/sndbuf&gt;
    &lt;/tune&gt;</b>
4974 4975 4976
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
4977 4978 4979

    <p>
      For tuning the backend of the network, the <code>backend</code> element
4980 4981
      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.
4982 4983
      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
4984 4985 4986 4987 4988 4989
      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>
4990
    </p>
4991 4992
    <h5><a name="elementsNICSTargetOverride">Overriding the target element</a></h5>

4993
<pre>
4994 4995 4996 4997 4998 4999 5000 5001
...
&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>
5002 5003

    <p>
E
Eric Blake 已提交
5004 5005
      If no target is specified, certain hypervisors will
      automatically generate a name for the created tun device. This
5006
      name can be manually specified, however the name <i>should not
E
Eric Blake 已提交
5007 5008
      start with either 'vnet' or 'vif'</i>, which are prefixes
      reserved by libvirt and certain hypervisors. Manually specified
5009
      targets using these prefixes may be ignored.
5010 5011
    </p>

5012 5013 5014 5015 5016 5017 5018 5019
    <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>
5020 5021 5022 5023 5024 5025 5026 5027
...
&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>
5028

5029 5030 5031
    <h5><a name="elementsNICSBoot">Specifying boot order</a></h5>

<pre>
5032 5033 5034 5035 5036 5037 5038 5039 5040
...
&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>
5041 5042

    <p>
5043
      For hypervisors which support this, you can set a specific NIC to
5044 5045 5046 5047 5048 5049 5050 5051
      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>

5052 5053 5054
    <h5><a name="elementsNICSROM">Interface ROM BIOS configuration</a></h5>

<pre>
5055 5056 5057 5058 5059 5060 5061 5062 5063
...
&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>
5064 5065 5066 5067 5068 5069 5070 5071 5072 5073

    <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
5074 5075 5076 5077 5078 5079
      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>.
5080
    </p>
5081 5082
    <h5><a name="elementDomain">Setting up a network backend in a driver domain</a></h5>
<pre>
5083 5084
...
&lt;devices&gt;
5085
  ...
5086 5087 5088 5089 5090 5091 5092
  &lt;interface type='bridge'&gt;
    &lt;source bridge='br0'/&gt;
    <b>&lt;backenddomain name='netvm'/&gt;</b>
  &lt;/interface&gt;
  ...
&lt;/devices&gt;
...</pre>
5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103

    <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>
5104

5105 5106 5107
    <h5><a name="elementQoS">Quality of service</a></h5>

<pre>
5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119
...
&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>
5120 5121 5122

    <p>
      This part of interface XML provides setting quality of service. Incoming
J
John Ferlan 已提交
5123 5124 5125 5126
      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.
5127 5128
    </p>

5129 5130 5131
    <h5><a name="elementVlanTag">Setting VLAN tag (on supported network types only)</a></h5>

<pre>
5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151
...
&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>
5152 5153 5154

    <p>
      If (and only if) the network connection used by the guest
5155
      supports VLAN tagging transparent to the guest, an
5156
      optional <code>&lt;vlan&gt;</code> element can specify one or
5157 5158 5159 5160 5161 5162 5163 5164 5165
      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
5166
      1.3.5</span>. All other connection types, including standard
5167 5168 5169
      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
5170 5171 5172 5173 5174 5175 5176 5177 5178
      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
5179
      attribute <code>trunk='yes'</code> can be added to the toplevel
5180 5181
      <code>&lt;vlan&gt;</code> element to differentiate trunking of a
      single tag from normal tagging.
5182
    </p>
5183
    <p>
5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194
      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.
5195 5196
    </p>

5197
    <h5><a name="elementLink">Modifying virtual link state</a></h5>
5198
<pre>
5199 5200 5201 5202 5203 5204 5205 5206 5207
...
&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>
5208 5209 5210 5211 5212 5213 5214 5215 5216 5217

    <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>

5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236
    <h5><a name="mtu">MTU configuration</a></h5>
<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>

5237 5238
    <h5><a name="ipconfig">IP configuration</a></h5>
<pre>
5239 5240 5241 5242 5243 5244 5245 5246 5247 5248
...
&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;
5249
  ...
5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260
  &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;

&lt;/devices&gt;
...
5261 5262 5263
</pre>

    <p>
5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278
      <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>.
5279 5280
    </p>

5281
    <p>
5282 5283 5284 5285 5286 5287
    <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.
5288 5289
    </p>

5290
<pre>
5291 5292 5293 5294 5295 5296 5297 5298
...
&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>
5299
    ...
5300
  &lt;/interface&gt;
5301
  ...
5302 5303
&lt;/devices&gt;
...
5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315
</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>

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5316 5317 5318 5319 5320 5321 5322 5323 5324 5325
    <h5><a name="elementVhostuser">vhost-user interface</a></h5>

    <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>
5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340
...
&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;
    &lt;source type='unix' path='/tmp/vhost2.sock' mode='client'/&gt;
    &lt;model type='virtio'/&gt;
    &lt;driver queues='5'/&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
M
Michele Paolino 已提交
5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352

    <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.
    </p>

5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364
    <h5><a name="elementNwfilter">Traffic filtering with NWFilter</a></h5>

    <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>
5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376
...
&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;
5377
      ...
5378 5379 5380 5381
    &lt;/filterref&gt;
  &lt;/interface&gt;
&lt;/devices&gt;
...</pre>
5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392

    <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>


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5393 5394 5395
    <h4><a name="elementsInput">Input devices</a></h4>

    <p>
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5396 5397 5398 5399
      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
5400 5401 5402
      to provide a graphics tablet for absolute cursor movement.
    </p>

5403
<pre>
5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415
...
&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
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5416 5417 5418

    <dl>
      <dt><code>input</code></dt>
E
Eric Blake 已提交
5419
      <dd>The <code>input</code> element has one mandatory attribute,
5420 5421 5422
        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'.
5423 5424
        The tablet provides absolute cursor movement,
        while the mouse uses relative movement. The optional
M
Matthew Booth 已提交
5425
        <code>bus</code> attribute can be used to refine the exact device type.
5426 5427
        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
5428 5429
    </dl>

E
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5430 5431 5432
    <p>
      The <code>input</code> element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
5433 5434
      device to a particular PCI
      slot, <a href="#elementsAddress">documented above</a>.
5435 5436 5437 5438

      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)
E
Eric Blake 已提交
5439
    </p>
D
Daniel P. Berrange 已提交
5440

M
Marc-André Lureau 已提交
5441 5442 5443 5444 5445 5446 5447 5448 5449
    <h4><a name="elementsHub">Hub devices</a></h4>

    <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>
5450 5451 5452 5453 5454
...
&lt;devices&gt;
  &lt;hub type='usb'/&gt;
&lt;/devices&gt;
...</pre>
M
Marc-André Lureau 已提交
5455 5456 5457 5458 5459 5460 5461 5462 5463

    <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
5464 5465 5466 5467
      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>.
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5468 5469
    </p>

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Daniel P. Berrange 已提交
5470 5471 5472 5473 5474 5475 5476 5477 5478
    <h4><a name="elementsGraphics">Graphical framebuffers</a></h4>

    <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>

5479
<pre>
5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492
...
&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
5493 5494 5495

    <dl>
      <dt><code>graphics</code></dt>
5496 5497 5498 5499 5500 5501
      <dd>
        <p>
          The <code>graphics</code> element has a mandatory <code>type</code>
          attribute which takes the value <code>sdl</code>, <code>vnc</code>,
          <code>spice</code>, <code>rdp</code> or <code>desktop</code>:
        </p>
5502
        <dl>
5503
          <dt><code>sdl</code></dt>
5504
          <dd>
5505 5506 5507 5508 5509 5510 5511
            <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>
5512
          </dd>
5513
          <dt><code>vnc</code></dt>
5514
          <dd>
5515 5516 5517 5518 5519
            <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
5520 5521 5522 5523
              port to use. The <code>passwd</code> attribute provides a VNC
              password in clear text. 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 an timestamp
5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551
              <code>passwdValidTo='2010-04-09T15:51:00'</code> assumed to be
              in UTC. The <code>connected</code> attribute allows control of
              connected client during password changes. VNC accepts
              <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>
5552
          </dd>
5553
          <dt><code>spice</code> <span class="since">Since 0.8.6</span></dt>
5554
          <dd>
E
Eric Blake 已提交
5555
            <p>
5556 5557 5558 5559 5560
              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
5561 5562 5563 5564 5565 5566
              auto-allocation of needed port numbers. The <code>passwd</code>
              attribute provides a SPICE password in clear text. 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
              an timestamp <code>passwdValidTo='2010-04-09T15:51:00'</code>
              assumed to be in UTC.
5567 5568 5569 5570 5571 5572 5573
            </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.
5574
              <span class="since">Since 0.9.3</span>
5575 5576
            </p>
            <p>
5577 5578
              The <code>defaultMode</code> attribute sets the default channel
              security policy, valid values are <code>secure</code>,
5579 5580 5581 5582
              <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
5583 5584
            </p>
            <p>
5585 5586 5587 5588 5589 5590 5591 5592
              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
5593
              <code>any</code> as mode discards the entry as the channel would
5594 5595 5596
              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>
5597
              (all <span class="since"> since 0.8.6</span>);
5598 5599
              <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
5600 5601
            </p>
            <pre>
5602 5603 5604 5605 5606 5607 5608 5609 5610 5611
&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;
  &lt;gl enable='yes'/&gt;
&lt;/graphics&gt;</pre>
5612
            <p>
5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624
              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>
5625
            </p>
5626
            <p>
5627 5628 5629 5630
              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>
5631
            </p>
5632
            <p>
5633 5634 5635 5636
              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>
5637
            </p>
P
Peng Zhou 已提交
5638
            <p>
5639 5640 5641 5642
              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
5643
            </p>
5644 5645
            <p>
              File transfer functionality (via Spice agent) is set using the
5646 5647 5648
              <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>
5649
            </p>
5650
            <p>
5651 5652 5653
              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>
5654
              property. (QEMU only, <span class="since">since 1.3.3</span>).
5655
            </p>
5656
          </dd>
5657
          <dt><code>rdp</code></dt>
5658
          <dd>
5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670
            <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
              use. The <code>replaceUser</code> attribute is a boolean deciding
              whether multiple simultaneous connections to the VM are permitted.
              The <code>multiUser</code> attribute is a boolean deciding whether
              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>
5671
          </dd>
5672
          <dt><code>desktop</code></dt>
5673
          <dd>
5674 5675 5676 5677 5678 5679 5680
            <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>
5681 5682 5683 5684 5685
          </dd>
        </dl>
      </dd>
    </dl>

5686
    <p>
5687 5688 5689 5690 5691 5692
      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:
5693 5694 5695
    </p>
    <dl>
      <dt><code>address</code></dt>
5696 5697 5698 5699 5700 5701 5702
      <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>
5703 5704 5705 5706 5707 5708 5709 5710 5711
        <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>
5712 5713
      </dd>
      <dt><code>network</code></dt>
5714 5715 5716 5717 5718 5719 5720 5721 5722 5723 5724 5725 5726 5727 5728
      <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>
5729
      </dd>
5730
      <dt><code>socket</code> <span class="since">since 2.0.0 (QEMU only)</span></dt>
5731 5732 5733 5734 5735
      <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.
5736
          Supported by graphics type <code>vnc</code> and <code>spice</code>.
5737 5738 5739 5740 5741 5742 5743
        </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.
5744 5745
        </p>
      </dd>
5746
      <dt><code>none</code> <span class="since">since 2.0.0 (QEMU only)</span></dt>
P
Pavel Hrdina 已提交
5747 5748 5749 5750 5751 5752 5753
      <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
5754 5755
          this graphics device. Supported by graphics type <code>vnc</code> and
          <code>spice</code>.
P
Pavel Hrdina 已提交
5756 5757
        </p>
      </dd>
5758 5759
    </dl>

5760 5761 5762 5763 5764
    <h4><a name="elementsVideo">Video devices</a></h4>
    <p>
      A video device.
    </p>

5765
<pre>
5766 5767 5768 5769 5770 5771 5772 5773 5774
...
&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>
5775 5776 5777

    <dl>
      <dt><code>video</code></dt>
5778
      <dd>
5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792
        <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
5793 5794
          video device. The non-primary must be type of "qxl" or
          (<span class="since">since 2.4.0</span>) "virtio".
5795
        </p>
5796
      </dd>
5797

5798 5799
      <dt><code>model</code></dt>
      <dd>
5800 5801 5802
        <p>
          The <code>model</code> element has a mandatory <code>type</code>
          attribute which takes the value "vga", "cirrus", "vmvga", "xen",
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          "vbox", "qxl" (<span class="since">since 0.8.6</span>) or
          "virtio" (<span class="since">since 1.3.0</span>)
          depending on the hypervisor features available.
5806 5807 5808 5809
        </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
5810
          type of "libxl", "vz", "qemu", "vbox", "vmx" and "xen". If no
5811 5812 5813 5814 5815
          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
5816
          supported only for guests type of "vz", "kvm", "vbox" and "vmx".
5817 5818
        </p>
        <p>
5819 5820 5821
          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
5822
          attribute <code>vram</code> specifies the secondary bar size.
5823 5824 5825 5826 5827
          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.
5828
          Attribute <code>vram64</code> (<span class="since">since 1.3.3</span>)
5829
          extends secondary bar and makes it addressable as 64bit memory.
5830
        </p>
5831 5832 5833 5834
      </dd>

      <dt><code>acceleration</code></dt>
      <dd>
5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845
        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>
5846
      </dd>
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5847 5848 5849 5850 5851 5852

      <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.
      </dd>
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    </dl>

5855
    <h4><a name="elementsConsole">Consoles, serial, parallel &amp; channel devices</a></h4>
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    <p>
      A character device provides a way to interact with the virtual machine.
5859 5860
      Paravirtualized consoles, serial ports, parallel ports and channels are
      all classed as character devices and so represented using the same syntax.
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5861 5862
    </p>

5863
<pre>
5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889
...
&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>
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5891 5892 5893 5894 5895
    <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
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5896

5897 5898 5899 5900 5901 5902
    <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>

5903 5904 5905 5906 5907 5908 5909 5910
    <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>

5911 5912 5913 5914 5915 5916 5917 5918
    <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>

5919
    <p>
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5920
      Regardless of the <code>type</code>, character devices can
5921 5922
      have an optional log file associated with them. This is
      expressed via a <code>log</code> sub-element, with a
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Boris Fiuczynski 已提交
5923 5924 5925
      <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>.
5926 5927 5928
    </p>

    <pre>
5929 5930 5931
...
&lt;log file="/var/log/libvirt/qemu/guestname-serial0.log" append="off"/&gt;
...</pre>
5932

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5933 5934 5935 5936 5937 5938 5939 5940
    <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>

5941 5942 5943 5944 5945 5946 5947 5948 5949
    <h5><a name="elementsCharGuestInterface">Guest interface</a></h5>

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

    <h6><a name="elementCharParallel">Parallel port</a></h6>

5950
<pre>
5951 5952 5953 5954 5955 5956 5957 5958
...
&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>
5959 5960 5961

    <p>
      <code>target</code> can have a <code>port</code> attribute, which
5962
      specifies the port number. Ports are numbered starting from 0. There are
5963 5964 5965 5966 5967
      usually 0, 1 or 2 parallel ports.
    </p>

    <h6><a name="elementCharSerial">Serial port</a></h6>

5968
<pre>
5969 5970 5971 5972 5973 5974 5975 5976
...
&lt;devices&gt;
  &lt;serial type='pty'&gt;
    &lt;source path='/dev/pts/3'/&gt;
    &lt;target port='0'/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
5977 5978 5979

    <p>
      <code>target</code> can have a <code>port</code> attribute, which
5980
      specifies the port number. Ports are numbered starting from 0. There are
G
Guannan Ren 已提交
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      usually 0, 1 or 2 serial ports. There is also an optional
      <code>type</code> attribute <span class="since">since 1.0.2</span>
M
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5983 5984 5985 5986 5987 5988 5989 5990 5991 5992
      which has three choices for its value, one is <code>isa-serial</code>,
      then <code>usb-serial</code> and last one is <code>pci-serial</code>.
      If <code>type</code> is missing, <code>isa-serial</code> will be used by
      default. For <code>usb-serial</code> an optional sub-element
      <code>&lt;address/&gt;</code> with <code>type='usb'</code> can tie the
      device to a particular controller, <a href="#elementsAddress">documented above</a>.
      Similarly, <code>pci-serial</code> can be used to attach the device to
      the pci bus (<span class="since">since 1.2.16</span>). Again, it has
      optional sub-element <code>&lt;address/&gt;</code> with
      <code>type='pci'</code> to select desired location on the PCI bus.
5993 5994 5995 5996 5997
    </p>

    <h6><a name="elementCharConsole">Console</a></h6>

    <p>
5998 5999 6000 6001 6002 6003 6004
      The console element is used to represent interactive consoles. Depending
      on the type of guest in use, the consoles might be paravirtualized devices,
      or they might be a clone of a serial device, according to the following
      rules:
    </p>

    <ul>
6005
      <li>If no <code>targetType</code> attribute is set, then the default
6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018
        device type is according to the hypervisor's rules. The default
        type will be added when re-querying the XML fed into libvirt.
        For fully virtualized guests, the default device type will usually
        be a serial port.</li>
      <li>If the <code>targetType</code> attribute is <code>serial</code>,
        then if no <code>&lt;serial&gt;</code> element exists, the console
        element will be copied to the serial element. If a <code>&lt;serial&gt;</code>
        element does already exist, the console element will be ignored.</li>
      <li>If the <code>targetType</code> attribute is not <code>serial</code>,
        it will be treated normally.</li>
      <li>Only the first <code>console</code> element may use a <code>targetType</code>
        of <code>serial</code>. Secondary consoles must all be paravirtualized.
      </li>
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      <li>On S390, the <code>console</code> element may use a
6020
        <code>targetType</code> of <code>sclp</code> or <code>sclplm</code>
B
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6021
        (line mode). SCLP is the native console type for S390. There's no
6022 6023 6024
        controller associated to SCLP consoles.
        <span class="since">Since 1.0.2</span>
      </li>
6025
    </ul>
C
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6026 6027 6028 6029 6030 6031

    <p>
      A virtio console device is exposed in the
      guest as /dev/hvc[0-7] (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>
6032 6033
    </p>

6034
<pre>
6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048
...
&lt;devices&gt;
  &lt;console type='pty'&gt;
    &lt;source path='/dev/pts/4'/&gt;
    &lt;target port='0'/&gt;
  &lt;/console&gt;

  &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>
6049

6050
<pre>
6051 6052 6053 6054 6055 6056 6057 6058 6059
...
&lt;devices&gt;
  &lt;!-- KVM S390 sclp console --&gt;
  &lt;console type='pty'&gt;
    &lt;source path='/dev/pts/1'/&gt;
    &lt;target type='sclp' port='0'/&gt;
  &lt;/console&gt;
&lt;/devices&gt;
...</pre>
6060

6061 6062 6063 6064 6065 6066
    <p>
      If the console is presented as a serial port, the <code>target</code>
      element has the same attributes as for a serial port. There is usually
      only 1 console.
    </p>

6067 6068 6069 6070 6071 6072 6073
    <h6><a name="elementCharChannel">Channel</a></h6>

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

6074
<pre>
6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091 6092 6093 6094
...
&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>
6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108

    <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>
6109 6110 6111

      <dt><code>virtio</code></dt>
      <dd>Paravirtualized virtio channel. Channel is exposed in the guest under
E
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6112
        /dev/vport*, and if the optional element <code>name</code> is specified,
6113
        /dev/virtio-ports/$name (for more info, please see
E
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6114 6115
        <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
6116 6117
        particular <code>type='virtio-serial'</code>
        controller, <a href="#elementsAddress">documented above</a>.
D
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6118 6119 6120 6121
        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
6122
        since 0.9.10</span> Moreover, <span class="since">since 1.0.6</span>
6123 6124 6125 6126
        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
6127 6128 6129 6130 6131 6132
        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>.
6133
      </dd>
J
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6134 6135 6136 6137 6138 6139 6140 6141 6142 6143
      <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>
6144 6145 6146 6147 6148 6149 6150 6151 6152 6153 6154 6155 6156
      <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>
6157 6158
    </dl>

6159 6160 6161 6162 6163 6164
    <h5><a name="elementsCharHostInterface">Host interface</a></h5>

    <p>
      A character device presents itself to the host as one of the following
      types.
    </p>
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6165

6166
    <h6><a name="elementsCharSTDIO">Domain logfile</a></h6>
D
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6167 6168 6169 6170 6171 6172

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

6173
<pre>
6174 6175 6176 6177 6178 6179 6180
...
&lt;devices&gt;
  &lt;console type='stdio'&gt;
    &lt;target port='1'/&gt;
  &lt;/console&gt;
&lt;/devices&gt;
...</pre>
D
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6181 6182


6183
    <h6><a name="elementsCharFle">Device logfile</a></h6>
D
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6184 6185 6186 6187 6188 6189

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

6190
<pre>
6191 6192 6193 6194 6195 6196 6197 6198
...
&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
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6199

6200
    <h6><a name="elementsCharVC">Virtual console</a></h6>
D
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6201 6202 6203 6204 6205 6206 6207

    <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>

6208
<pre>
6209 6210 6211 6212 6213 6214 6215
...
&lt;devices&gt;
  &lt;serial type='vc'&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
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6216

6217
    <h6><a name="elementsCharNull">Null device</a></h6>
D
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6218 6219 6220 6221 6222 6223

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

6224
<pre>
6225 6226 6227 6228 6229 6230 6231
...
&lt;devices&gt;
  &lt;serial type='null'&gt;
    &lt;target port="1"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
D
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6232

6233
    <h6><a name="elementsCharPTY">Pseudo TTY</a></h6>
D
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6234 6235 6236 6237 6238 6239 6240

    <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>

6241
<pre>
6242 6243 6244 6245 6246 6247 6248 6249
...
&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
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6250 6251 6252

    <p>
      NB special case if &lt;console type='pty'&gt;, then the TTY
A
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6253
      path is also duplicated as an attribute tty='/dev/pts/3'
D
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6254 6255 6256 6257
      on the top level &lt;console&gt; tag. This provides compat
      with existing syntax for &lt;console&gt; tags.
    </p>

6258
    <h6><a name="elementsCharHost">Host device proxy</a></h6>
D
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6259 6260 6261 6262 6263

    <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
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6264
      a host serial port - don't connect a serial port to a parallel
D
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6265 6266 6267
      port.
    </p>

6268
<pre>
6269 6270 6271 6272 6273 6274 6275 6276
...
&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
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6277

6278
    <h6><a name="elementsCharPipe">Named pipe</a></h6>
6279 6280 6281 6282 6283 6284

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

6285
<pre>
6286 6287 6288 6289 6290 6291 6292 6293
...
&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>
6294

6295
    <h6><a name="elementsCharTCP">TCP client/server</a></h6>
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    <p>
      The character device acts as a TCP client connecting to a
6299
      remote server.
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    </p>

6302
<pre>
6303 6304 6305 6306 6307 6308 6309 6310 6311
...
&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>
6312 6313 6314 6315 6316

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

6317
<pre>
6318 6319 6320 6321 6322 6323 6324 6325 6326
...
&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>
6327 6328

    <p>
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      Alternatively you can use <code>telnet</code> instead
J
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      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.
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6337
    </p>
6338

6339
<pre>
6340 6341 6342 6343 6344 6345 6346
...
&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;
6347
  ...
6348 6349 6350 6351 6352 6353 6354
  &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>
6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373

    <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>
6374 6375 6376 6377 6378 6379 6380 6381 6382
...
&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>
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6384
    <h6><a name="elementsCharUDP">UDP network console</a></h6>
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    <p>
      The character device acts as a UDP netconsole service,
      sending and receiving packets. This is a lossy service.
    </p>

6391
<pre>
6392 6393 6394 6395 6396 6397 6398 6399 6400
...
&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>
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6401

6402
    <h6><a name="elementsCharUNIX">UNIX domain socket client/server</a></h6>
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6403 6404 6405 6406 6407 6408

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

6409
<pre>
6410 6411 6412 6413 6414 6415 6416 6417
...
&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>
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6418

6419 6420 6421 6422 6423 6424 6425
    <h6><a name="elementsCharSpiceport">Spice channel</a></h6>

    <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>
6426 6427 6428 6429 6430
    <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>
6431 6432

<pre>
6433 6434 6435 6436 6437 6438 6439 6440
...
&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>
6441

6442 6443 6444 6445
    <h6><a name="elementsNmdm">Nmdm device</a></h6>

    <p>
      The nmdm device driver, available on FreeBSD, provides two
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      tty devices connected together by a virtual null modem cable.
6447 6448 6449 6450
      <span class="since">Since 1.2.4</span>
    </p>

<pre>
6451 6452 6453 6454 6455 6456 6457
...
&lt;devices&gt;
  &lt;serial type="nmdm"&gt;
    &lt;source master="/dev/nmdm0A" slave="/dev/nmdm0B"/&gt;
  &lt;/serial&gt;
&lt;/devices&gt;
...</pre>
6458 6459 6460 6461 6462 6463 6464

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

    <dl>
      <dt><code>master</code></dt>
6465 6466
      <dd>Master device of the pair, that is passed to the hypervisor.
      Device is specified by a fully qualified path.</dd>
6467 6468 6469

      <dt><code>slave</code></dt>
      <dd>Slave device of the pair, that is passed to the clients for connection
6470
      to the guest console. Device is specified by a fully qualified path.</dd>
6471
    </dl>
6472 6473 6474 6475 6476 6477 6478 6479

    <h4><a name="elementsSound">Sound devices</a></h4>

    <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>

6480
<pre>
6481 6482 6483 6484 6485
...
&lt;devices&gt;
  &lt;sound model='es1370'/&gt;
&lt;/devices&gt;
...</pre>
6486 6487 6488 6489 6490 6491 6492

    <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
6493
        choices are 'es1370', 'sb16', 'ac97', 'ich6' and 'usb'.
6494
        (<span class="since">
6495 6496
         'ac97' only since 0.6.0, 'ich6' only since 0.8.8,
         'usb' only since 1.2.7</span>)
6497 6498 6499
      </dd>
    </dl>

6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510
    <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
      will be attached to allow playback and recording. Valid values
      are 'duplex' (advertise a line-in and a line-out) and 'micro'
      (advertise a speaker and a microphone).
    </p>

<pre>
6511 6512 6513 6514 6515 6516 6517
...
&lt;devices&gt;
  &lt;sound model='ich6'&gt;
    &lt;codec type='micro'/&gt;
  &lt;/sound&gt;
&lt;/devices&gt;
...</pre>
6518

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6519 6520 6521
    <p>
      Each <code>sound</code> element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
6522 6523
      device to a particular PCI
      slot, <a href="#elementsAddress">documented above</a>.
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6524 6525
    </p>

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6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545
    <h4><a name="elementsWatchdog">Watchdog device</a></h4>

    <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>

6546
<pre>
6547 6548 6549 6550 6551
...
&lt;devices&gt;
  &lt;watchdog model='i6300esb'/&gt;
&lt;/devices&gt;
...</pre>
R
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6552

6553 6554 6555 6556 6557 6558
<pre>
  ...
  &lt;devices&gt;
    &lt;watchdog model='i6300esb' action='poweroff'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>
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6559 6560 6561 6562

    <dl>
      <dt><code>model</code></dt>
      <dd>
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        <p>
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6564
        The required <code>model</code> attribute specifies what real
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6565 6566 6567 6568 6569 6570 6571 6572 6573 6574
        watchdog device is emulated.  Valid values are specific to the
        underlying hypervisor.
        </p>
        <p>
        QEMU and KVM support:
        </p>
        <ul>
          <li> 'i6300esb' &mdash; the recommended device,
            emulating a PCI Intel 6300ESB </li>
          <li> 'ib700' &mdash; emulating an ISA iBase IB700 </li>
6575
          <li> 'diag288' &mdash; emulating an S390 DIAG288 device
6576
            <span class="since">Since 1.2.17</span></li>
M
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6577
        </ul>
R
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6578 6579 6580
      </dd>
      <dt><code>action</code></dt>
      <dd>
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6581
        <p>
R
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6582
        The optional <code>action</code> attribute describes what
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        action to take when the watchdog expires.  Valid values are
        specific to the underlying hypervisor.
        </p>
        <p>
        QEMU and KVM support:
        </p>
        <ul>
          <li>'reset' &mdash; default, forcefully reset the guest</li>
          <li>'shutdown' &mdash; gracefully shutdown the guest
            (not recommended) </li>
          <li>'poweroff' &mdash; forcefully power off the guest</li>
          <li>'pause' &mdash; pause the guest</li>
          <li>'none' &mdash; do nothing</li>
6596 6597
          <li>'dump' &mdash; automatically dump the guest
            <span class="since">Since 0.8.7</span></li>
6598 6599
          <li>'inject-nmi' &mdash; inject a non-maskable interrupt
            into the guest
6600
            <span class="since">Since 1.2.17</span></li>
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6601 6602
        </ul>
        <p>
6603
        Note 1: the 'shutdown' action requires that the guest
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6604 6605 6606 6607 6608
        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>
6609 6610 6611 6612
        <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>
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6613 6614 6615
      </dd>
    </dl>

6616 6617 6618 6619 6620 6621 6622 6623 6624
    <h4><a name="elementsMemBalloon">Memory balloon device</a></h4>

    <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>
6625 6626 6627
      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.
6628 6629 6630
    </p>

    <p>
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6631
      Example: automatically added device with KVM
6632 6633
    </p>
<pre>
6634 6635 6636 6637 6638
...
&lt;devices&gt;
  &lt;memballoon model='virtio'/&gt;
&lt;/devices&gt;
...</pre>
6639 6640

    <p>
J
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6641
      Example: manually added device with static PCI slot 2 requested
6642 6643 6644 6645
    </p>
<pre>
  ...
  &lt;devices&gt;
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6646 6647
    &lt;memballoon model='virtio'&gt;
      &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/&gt;
6648
      &lt;stats period='10'/&gt;
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6649
    &lt;/memballoon&gt;
6650 6651 6652 6653 6654 6655 6656 6657
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The required <code>model</code> attribute specifies what type
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6658 6659
          of balloon device is provided. Valid values are specific to
          the virtualization platform
6660 6661 6662 6663 6664 6665
        </p>
        <ul>
          <li>'virtio' &mdash; default with QEMU/KVM</li>
          <li>'xen' &mdash; default with Xen</li>
        </ul>
      </dd>
6666 6667 6668 6669 6670 6671 6672 6673 6674 6675
      <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>
6676 6677 6678
      <dt><code>period</code></dt>
      <dd>
        <p>
6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689
          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.
6690 6691 6692
          <span class='since'>Since 1.1.1, requires QEMU 1.5</span>
        </p>
      </dd>
6693
    </dl>
6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705
    <h4><a name="elementsRng">Random number generator device</a></h4>

    <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>
6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718
...
&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;
...
6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731
</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>
          <li>'virtio' &mdash; supported by qemu and virtio-rng kernel module</li>
        </ul>
      </dd>
6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743
      <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>
6744 6745 6746 6747 6748 6749 6750
      <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>
6751 6752 6753 6754 6755
        <dl>
          <dt><code>random</code></dt>
          <dd>
            <p>
              This backend type expects a non-blocking character device as
6756
              input. The file name is specified as contents of the
6757 6758 6759 6760
              <code>backend</code> element. <span class='since'>Since 1.3.4</span>
              any path is accepted. Before that /dev/random and /dev/hwrng were
              the only accepted paths. When no file name is specified the hypervisor
              default is used. For qemu, the default is /dev/random
6761 6762 6763 6764 6765 6766 6767 6768 6769 6770 6771 6772
            </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>
6773 6774 6775
      </dd>

    </dl>
6776

6777 6778 6779 6780 6781 6782 6783 6784
    <h4><a name="elementsTpm">TPM device</a></h4>

    <p>
      The TPM device enables a QEMU guest to have access to TPM
      functionality.
    </p>
    <p>
      The TPM passthrough device type provides access to the host's TPM
6785
      for one QEMU guest. No other software may be using the TPM device,
6786 6787 6788 6789 6790 6791 6792 6793
      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>
6794 6795 6796 6797 6798 6799 6800 6801 6802
...
&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;
...
6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818
</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.
        </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>
6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833
        <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>
6834 6835 6836
      </dd>
    </dl>

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6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847
    <h4><a name="elementsNVRAM">NVRAM device</a></h4>
    <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>
6848 6849 6850 6851 6852 6853 6854
...
&lt;devices&gt;
  &lt;nvram&gt;
    &lt;address type='spapr-vio' reg='0x3000'/&gt;
  &lt;/nvram&gt;
&lt;/devices&gt;
...
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</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>

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    <h4><a name="elementsPanic">panic device</a></h4>
    <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>
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    <p>
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      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.
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    </p>
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    <p>
      Example: usage of panic configuration
    </p>
<pre>
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...
&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>
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    <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>
          <li>'isa' &mdash; for ISA pvpanic device</li>
          <li>'pseries' &mdash; default and valid only for pSeries guests.</li>
          <li>'hyperv' &mdash; for Hyper-V crash CPU feature.
            <span class="since">Since 1.3.0, QEMU and KVM only</span></li>
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          <li>'s390' &mdash; default for S390 guests.
            <span class="since">Since 1.3.5</span></li>
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        </ul>
      </dd>
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    <dt><code>address</code></dt>
    <dd>
      <p>
        address of panic. The default ioport is 0x505. Most users
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        don't need to specify an address, and doing so is forbidden
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        altogether for s390, pseries and hyperv models.
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      </p>
    </dd>
  </dl>

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  <h4><a name="elementsShmem">Shared memory device</a></h4>

    <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>
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...
&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;
...
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</pre>

  <dl>
    <dt><code>shmem</code></dt>
    <dd>
      The <code>shmem</code> element has one mandatory attribute,
      <code>name</code> to identify the shared memory.
    </dd>
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    <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
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      <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).
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    </dd>
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    <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
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      <code>path</code> attribute specifies the absolute path to the unix socket
      and defaults to <code>/var/lib/libvirt/shmem/$shmem-$name-sock</code>.
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    </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>

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    <h4><a name="elementsMemory">Memory devices</a></h4>

    <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.
      <span class="since">Since 1.2.14</span>
    </p>

    <p>
      Example: usage of the memory devices
    </p>
<pre>
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...
&lt;devices&gt;
  &lt;memory model='dimm'&gt;
    &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;
&lt;/devices&gt;
...
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</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          Currently only the <code>dimm</code> model is supported in order to
          add a virtual DIMM module to the guest.
        </p>
      </dd>

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

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    <h4><a name="elementsIommu">IOMMU devices</a></h4>

    <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>
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...
&lt;devices&gt;
  &lt;iommu model='intel'/&gt;
&lt;/devices&gt;
...
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</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          Currently only the <code>intel</code> model is supported.
        </p>
      </dd>
    </dl>

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    <h3><a name="seclabel">Security label</a></h3>

    <p>
      The <code>seclabel</code> element allows control over the
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      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
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      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
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      if desired.  <span class="since">'dynamic' since 0.6.1, 'static'
      since 0.6.2, and 'none' since 0.9.10.</span>
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    </p>

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    <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>

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    <p>
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      Valid input XML configurations for the top-level security label
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      are:
    </p>

    <pre>
7135
&lt;seclabel type='dynamic' model='selinux'/&gt;
7136

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&lt;seclabel type='dynamic' model='selinux'&gt;
  &lt;baselabel&gt;system_u:system_r:my_svirt_t:s0&lt;/baselabel&gt;
&lt;/seclabel&gt;
7140

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&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;
7144

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&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;
7148

7149
&lt;seclabel type='none'/&gt;
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    </pre>

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    <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>

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    <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>
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      <dd>Either <code>static</code>, <code>dynamic</code> or <code>none</code>
        to determine whether libvirt automatically generates a unique security
        label or not.
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      </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
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        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>
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      </dd>
      <dt><code>baselabel</code></dt>
      <dd>If dynamic labelling is used, this can optionally be
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        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.)
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      </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>

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    <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>

7233 7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248 7249 7250 7251 7252 7253 7254 7255 7256 7257 7258 7259 7260 7261 7262 7263 7264 7265 7266 7267 7268 7269 7270 7271
    <h3><a name="keywrap">Key Wrap</a></h3>

       <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>

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Daniel P. Berrange 已提交
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    <h2><a name="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>