XML:
<features>
  <hyperv>
    <vapic state='on'/>
    <spinlocks state='on' retries='4096'/>
  </hyperv>
</features>

results in the following QEMU command line:
qemu -cpu <cpu_model>,hv_vapic,hv_spinlocks=0x1000

https://bugzilla.redhat.com/show_bug.cgi?id=784836

Add new CPU features for HyperV:
vapic for virtual APIC support
spinlocks for setting spinlock support

<features>
  <hyperv>
    <vapic state='on'/>
    <spinlocks state='on' retries='4096'/>
  </hyperv>
</features>

https://bugzilla.redhat.com/show_bug.cgi?id=784836

https://bugzilla.redhat.com/show_bug.cgi?id=964177

Though both libvirt and QEMU's document say RTC_CHANGE returns
the offset from the host UTC, qemu actually returns the offset
from the specified date instead when specific date is provided
(-rtc base=$date).

It's not safe for qemu to fix it in code, it worked like that
for 3 years, changing it now may break other QEMU use cases.
What qemu tries to do is to fix the document:

http://lists.gnu.org/archive/html/qemu-devel/2013-05/msg04782.html

And in libvirt side, instead of replying on the value from qemu,
this converts the offset returned from qemu to the offset from
host UTC, by:

  /*
   * a: the offset from qemu RTC_CHANGE event
   * b: The specified date (-rtc base=$date)
   * c: the host date when libvirt gets the RTC_CHANGE event
   * offset: What libvirt will report
   */

  offset = a + (b - c);

The specified date (-rtc base=$date) is recorded in clock's def as
an internal only member (may be useful to exposed outside?).

Internal only XML tag "basetime" is introduced to not lose the
guest's basetime after libvirt restarting/reloading:

<clock offset='variable' adjustment='304' basis='utc' basetime='1370423588'/>

Use virStringSplit. Change the 'error' label to 'cleanup' to prevent
memory leaks on error.

Found with 'git grep "= 1"'.

Currently, if there's an error opening /dev/vhost-net (e.g. because
it doesn't exist) but it's not required we proceed with vhostfd array
filled with -1 and vhostfdSize unchanged. Later, when constructing
the qemu command line only non-negative items within vhostfd array
are taken into account. This means, vhostfdSize may be greater than
the actual count of non-negative items in vhostfd array. This results
in improper command line arguments being generated, e.g.:

-netdev tap,fd=21,id=hostnet0,vhost=on,vhostfd=(null)

With previous patch, we accept negative value as length of string to
duplicate. So there is no need to pass strlen(src) in case we want to do
duplicate the whole string.

In order to learn libvirt multiqueue several things must be done:

1) The '/dev/net/tun' device needs to be opened multiple times with
IFF_MULTI_QUEUE flag passed to ioctl(fd, TUNSETIFF, &ifr);

2) Similarly, '/dev/vhost-net' must be opened as many times as in 1)
in order to keep 1:1 ratio recommended by qemu and kernel folks.

3) The command line construction code needs to switch from 'fd=X' to
'fds=X:Y:...:Z' and from 'vhostfd=X' to 'vhostfds=X:Y:...:Z'.

4) The monitor handling code needs to learn to pass multiple FDs.

Currently, we have one huge function to construct qemu command line.
This is very ineffective esp. if there's a fault somewhere.

example: qemu ${otherargs} \
             -vnc 127.0.0.1:0,share=allow-exclusive

Since 0d70656a, it starts to access the sysfs files to build
the qemu command line (by virSCSIDeviceGetSgName, which is to find
out the scsi generic device name by adpater:bus:target:unit), there
is no way to work around, qemu wants to see the scsi generic device
like "/dev/sg6" anyway.

And there might be other places which need to access sysfs files
when building qemu command line in future.

Instead of increasing the arguments of qemuBuildCommandLine, this
introduces a new callback for qemuBuildCommandLine, and thus tests
can register their own callbacks for sysfs test input files accessing.

* src/qemu/qemu_command.h: (New callback struct
                            qemuBuildCommandLineCallbacks;
                            extern buildCommandLineCallbacks)
* src/qemu/qemu_command.c: (wire up the callback struct)
* src/qemu/qemu_driver.c: (Use the new syntax of qemuBuildCommandLine)
* src/qemu/qemu_hotplug.c: Likewise
* src/qemu/qemu_process.c: Likewise
* tests/testutilsqemu.[ch]: (Helper testSCSIDeviceGetSgName;
                             callback struct testCallbacks;)
* tests/qemuxml2argvtest.c: (Use testCallbacks)
* src/tests/qemuxmlnstest.c: (Like above)

QEMU introduced "discard" option for drive since commit a9384aff53,

<...>
@var{discard} is one of "ignore" (or "off") or "unmap" (or "on") and
controls whether @dfn{discard} (also known as @dfn{trim} or @dfn{unmap})
requests are ignored or passed to the filesystem.  Some machine types
may not support discard requests.
</...>

This patch exposes the support in libvirt.

QEMU supported "discard" for "-drive" since v1.5.0-rc0:

% git tag --contains a9384aff53
contains
v1.5.0-rc0
v1.5.0-rc1

So this only detects the capability bit using virQEMUCapsProbeQMPCommandLine.

During building of the qemu command line determine whether to add/use the
'-no-reboot' option only if each of the 'on' events want to to destroy
the domain; otherwise, use the '-no-shutdown' option.

Prior to this change both could be on the command line, which while allowed
could be construed as a conflict.

Adding a VNC WebSocket support for QEMU driver.  This functionality is
in upstream qemu from commit described as v1.3.0-982-g7536ee4, so the
capability is being recognized based on QEMU version for now.

QEMU introduced command line "-mem-merge=on|off" (defaults to on) to
enable/disable the memory merge (KSM) at guest startup. This exposes
it by new XML:
  <memoryBacking>
    <nosharepages/>
  </memoryBacking>

The XML tag is same with what we used internally for old RHEL.

The QEMU command line syntax for RBD disks is

   file=rbd:pool/image:opt1=val1:opt2=val2...

There is no way to escape the ':' if it appears in the
pool or image name. Thus it must be explicitly forbidden
if it occurs in the libvirt XML. People are known to
be abusing the lack of escaping in current libvirt to
pass arbitrary args to QEMU.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The <filesystem> element can now accept a <driver type='nbd'/>
as an alternative to 'loop'. The benefit of NBD is support
for non-raw disk image formats.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Extend the <driver> element in filesystem devices to
allow a storage format to be set. The new attribute
uses 'format' to reflect the storage format. This is
different from the <driver> element in disk devices
which use 'type' to reflect the storage format. This
is because the 'type' attribute on filesystem devices
is already used for the driver backend, for which the
disk devices use the 'name' attribute. Arggggh.

Anyway for disks we have

   <driver name="qemu" type="raw"/>

And for filesystems this change means we now have

   <driver type="loop" format="raw"/>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Since it's generic enough to be used by other types in future, I
put it in <hostdev> as sub-element, though now it's only used by
scsi host device.

Except the scsi host device's controller is "lsilogic", mapping
between the libvirt attributes and scsi-generic properties is:

  libvirt     qemu
-----------------------------------------
  controller  bus ($libvirt_controller.0)
  bus         channel
  target      scsi-id
  unit        lun

For scsi host device with "lsilogic" controller, the mapping is:
('target (libvirt)' must be 0, as it's not used; 'unit (libvirt)
must <= 7).

  libvirt            qemu
----------------------------------------------------------
  controller && bus  bus ($libvirt_controller.$libvirt_bus)
  unit               scsi-id

It's not good to hardcode/hard-check limits of these attributes,
and even worse, these limits are not documented, one has to find
out by either testing or reading the qemu code, I'm looking forward
to qemu expose limits like these one day). For example, exposing
"max_target", "max_lun" for megasas:

static const struct SCSIBusInfo megasas_scsi_info = {
    .tcq = true,
    .max_target = MFI_MAX_LD,
    .max_lun = 255,

    .transfer_data = megasas_xfer_complete,
    .get_sg_list = megasas_get_sg_list,
    .complete = megasas_command_complete,
    .cancel = megasas_command_cancel,
};

Example of the qemu command line (lsilogic controller):

  -drive file=/dev/sg2,if=none,id=drive-hostdev-scsi_host7-0-0-0 \
  -device scsi-generic,bus=scsi0.0,scsi-id=8,\
  drive=drive-hostdev-scsi_host7-0-0-0,id=hostdev-scsi_host7-0-0-0

Example of the qemu command line (virtio-scsi controller):

  -drive file=/dev/sg2,if=none,id=drive-hostdev-scsi_host7-0-0-0 \
  -device scsi-generic,bus=scsi0.0,channel=0,scsi-id=128,lun=128,\
  drive=drive-hostdev-scsi_host7-0-0-0,id=hostdev-scsi_host7-0-0-0
Signed-off-by: NHan Cheng <hanc.fnst@cn.fujitsu.com>
Signed-off-by: NOsier Yang <jyang@redhat.com>

Use virBufferAddLit or virBufferAddChar instead.

VFIO device assignment requires a cgroup ACL to be setup for access to
the /dev/vfio/nn "group" device for any devices that will be assigned
to a guest. In the case of a host device that is allocated from a
pool, it was being allocated during qemuBuildCommandLine(), which is
called by qemuProcessStart() *after* the all-encompassing
qemuSetupCgroup() was called, meaning that the standard Cgroup ACL
setup wasn't creating ACLs for these devices allocated from pools.

One possible solution was to manually add a single ACL down inside
qemuBuildCommandLine() when networkAllocateActualDevice() is called,
but that has two problems: 1) the function that adds the cgroup ACL
requires a virDomainObjPtr, which isn't available in
qemuBuildCommandLine(), and 2) we really shouldn't be doing network
device setup inside qemuBuildCommandLine() anyway.

Instead, I've created a new function called
qemuNetworkPrepareDevices() which is called just before
qemuPrepareHostDevices() during qemuProcessStart() (explanation of
ordering in the comments), i.e. well before the call to
qemuSetupCgroup(). To minimize code churn in a patch that will be
backported to 1.0.5-maint, qemuNetworkPrepareDevices only does
networkAllocateActualDevice() and the bare amount of setup required
for type='hostdev network devices, but it eventually should do *all*
device setup for guest network devices.

Note that some of the code that was previously needed in
qemuBuildCommandLine() is no longer required when
networkAllocateActualDevice() is called earlier:

 * qemuAssignDeviceHostdevAlias() is already done further down in
   qemuProcessStart().

 * qemuPrepareHostdevPCIDevices() is called by
   qemuPrepareHostDevices() which is called after
   qemuNetworkPrepareDevices() in qemuProcessStart().

As hinted above, this new function should be moved into a separate
qemu_network.c (or similarly named) file along with
qemuPhysIfaceConnect(), qemuNetworkIfaceConnect(), and
qemuOpenVhostNet(), and expanded to call those functions as well, then
the nnets loop in qemuBuildCommandLine() should be reduced to only
build the commandline string (which itself can be in a separate
qemuInterfaceBuilldCommandLine() function as suggested by
Michal). However, this will require storing away an array of tapfd and
vhostfd that are needed for the commandline, so I would rather do that
in a separate patch and leave this patch at the minimum to fix the
bug.

The use of () in a simple boolean comparison was not
required
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The source code base needs to be adapted as well. Some files
include virutil.h just for the string related functions (here,
the include is substituted to match the new file), some include
virutil.h without any need (here, the include is removed), and
some require both.

As a result of commit id '19c345f2', 'make -C tests valgrind' has the
following for qemuxml2argvtest:

==22482== 197 (80 direct, 117 indirect) bytes in 1 blocks are definitely lost in loss record 101 of 120
==22482==    at 0x4A06B6F: calloc (vg_replace_malloc.c:593)
==22482==    by 0x4C6F301: virAlloc (viralloc.c:124)
==22482==    by 0x4C840FC: virSaveLastError (virerror.c:308)
==22482==    by 0x431882: qemuBuildCommandLine (qemu_command.c:8204)
==22482==    by 0x41E8F0: testCompareXMLToArgvHelper (qemuxml2argvtest.c:155)
==22482==    by 0x41FE9F: virtTestRun (testutils.c:157)
==22482==    by 0x419DEB: mymain (qemuxml2argvtest.c:654)
==22482==    by 0x4204DA: virtTestMain (testutils.c:719)
==22482==    by 0x39D0821A04: (below main) (libc-start.c:225)
==22482==

qemuBuildMemballoonDevStr returns NULL if memballoon doesn't have
the right address type, but it doesn't report an error, leading to:
error: An error occurred, but the cause is unknown

Report a helpful error message instead, e.g.:
error: XML error: memballoon unsupported with address type 'usb'

My commit 024e9af3 broke this.

Don't reserve slot 2 for video if the machine has no PCI buses.
Error out when the user specifies a video device without
a PCI address when there are no PCI buses.

(This wouldn't work on a machine with no PCI bus anyway since
we do add PCI addresses for video devices to the command line)

In the past we automatically added a USB controller and assigned
it a PCI address (0:0:1.2) even on machines without a PCI bus.
This didn't break machines with no PCI bus  because the command
line for it is just '-usb', with no mention of the PCI bus.

The implicit IDE controller (reserved address 0:0:1.1) has
no command line at all.

Commit b33eb0dc removed the ability to reserve PCI addresses
on machines without a PCI bus. This made them stop working,
since there would always be the implicit USB controller.

Skip the reservation of addresses for these controllers when
there is no PCI bus, instead of failing.

This isn't strictly speaking a bugfix, but I realized I'd gotten a bit
too verbose when I chose the names for
VIR_DOMAIN_HOSTDEV_PCI_BACKEND_TYPE_*. This shortens them all a bit.

<source type='bridge'> uses a helper application to do the necessary
TUN/TAP setup to use an existing network bridge, thus letting
unprivileged users use TUN/TAP interfaces.

However, libvirt should be preventing QEMU from running any setuid
programs at all, which would include this helper program.  From
a security POV, any setuid helper needs to be run by libvirtd itself,
not QEMU.

This is what this patch does.  libvirt now invokes the setuid helper,
gets the TAP fd and then passes it to QEMU in the normal manner.
The path to the helper is specified in qemu.conf.

As a small advantage, this adds a <target dev='tap0'/> element to the
XML of an active domain using <interface type='bridge'>.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Adjust the usb-none test, since it gives the memballoon a lower PCI slot now.
Add a test for 'none' controller on s390, which doesn't have PCI buses.

VFIO requires all of the guest's memory and IO space to be lockable in
RAM. The domain's max_balloon is the maximum amount of memory the
domain can have (in KiB). We add a generous 1GiB to that for IO space
(still much better than KVM device assignment, where the KVM module
actually *ignores* the process limits and locks everything anyway),
and convert from KiB to bytes.

In the case of hotplug, we are changing the limit for the already
existing qemu process (prlimit() is used under the hood), and for
regular commandline additions of vfio devices, we schedule a call to
setrlimit() that will happen after the qemu process is forked.

The device option for vfio-pci is nearly identical to that for
pci-assign - only the configfd parameter isn't supported (or needed).

Checking for presence of the bootindex parameter is done separately
from constructing the commandline, similar to how it is done for
pci-assign.

This patch contains tests to check for proper commandline
construction. It also includes tests for parser-formatter-parser
roundtrips (xml2xml), because those tests use the same data files, and
would have failed had they been included before now.

qemu: xml/args tests for VFIO hostdev and <interface type='hostdev'/>

These should be squashed in with the patch that adds commandline
handling of vfio (they would fail at any earlier time).