To avoid memory leak of the "backingStoreRaw" field when reparsing
backing chains a new function is being introduced by this patch that
shall be used to clear backing store information.

The memory leak was introduced in commit 8823272d.

Based on suggestion from Eric [1], because it might not get cleaned up
before the release, so to avoid potential errors.

[1] https://www.redhat.com/archives/libvir-list/2014-April/msg00929.htmlSigned-off-by: NMartin Kletzander <mkletzan@redhat.com>

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1019926
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=868673Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

To avoid having the root of a backing chain present twice in the list we
need to invert the working of virStorageFileGetMetadataRecurse.

Until now the recursive worker created a new backing chain element from
the name and other information passed as arguments. This required us to
pass the data of the parent in a deconstructed way and the worker
created a new entry for the parent.

This patch converts this function so that it just fills in metadata
about the parent and creates a backing chain element from those. This
removes the duplication of the first element.

To avoid breaking the test suite, virstoragetest now calls a wrapper
that creates the parent structure explicitly and pre-fills it with the
test data with same function signature as previously used.

Switch over to storing of the backing chain as a recursive
virStorageSource structure.

This is a string based move. Currently the first element will be present
twice in the backing chain as currently the retrieval function stores
the parent in the newly detected chain. This will be fixed later.

Replace the old structure with the new one. This change is a trivial
name change operation (along with change of the freeing function).

The function isn't used in any other source file. Move it so that it
doesn't need a declaration.

A continuation of the migration of disk details to virstoragefile.
This patch moves a single enum, but converting the name has quite
a bit of fallout.

* src/conf/domain_conf.h (virDomainDiskType): Move...
* src/util/virstoragefile.h (virStorageType): ...and rename.
* src/bhyve/bhyve_command.c (bhyveBuildDiskArgStr)
(virBhyveProcessBuildLoadCmd): Update clients.
* src/conf/domain_conf.c (virDomainDiskSourceDefParse)
(virDomainDiskDefParseXML, virDomainDiskSourceDefFormatInternal)
(virDomainDiskDefFormat, virDomainDiskGetActualType)
(virDomainDiskDefForeachPath, virDomainDiskSourceIsBlockType):
Likewise.
* src/conf/snapshot_conf.h (_virDomainSnapshotDiskDef): Likewise.
* src/conf/snapshot_conf.c (virDomainSnapshotDiskDefParseXML)
(virDomainSnapshotAlignDisks, virDomainSnapshotDiskDefFormat):
Likewise.
* src/esx/esx_driver.c (esxAutodetectSCSIControllerModel)
(esxDomainDefineXML): Likewise.
* src/locking/domain_lock.c (virDomainLockManagerAddDisk):
Likewise.
* src/lxc/lxc_controller.c
(virLXCControllerSetupLoopDeviceDisk)
(virLXCControllerSetupNBDDeviceDisk)
(virLXCControllerSetupLoopDevices, virLXCControllerSetupDisk):
Likewise.
* src/parallels/parallels_driver.c (parallelsGetHddInfo):
Likewise.
* src/phyp/phyp_driver.c (phypDiskType): Likewise.
* src/qemu/qemu_command.c (qemuGetDriveSourceString)
(qemuDomainDiskGetSourceString, qemuBuildDriveStr)
(qemuBuildCommandLine, qemuParseCommandLineDisk)
(qemuParseCommandLine): Likewise.
* src/qemu/qemu_conf.c (qemuCheckSharedDevice)
(qemuTranslateDiskSourcePool)
(qemuTranslateSnapshotDiskSourcePool): Likewise.
* src/qemu/qemu_domain.c (qemuDomainDeviceDefPostParse)
(qemuDomainDetermineDiskChain): Likewise.
* src/qemu/qemu_driver.c (qemuDomainGetBlockInfo)
(qemuDomainSnapshotPrepareDiskExternalBackingInactive)
(qemuDomainSnapshotPrepareDiskExternalBackingActive)
(qemuDomainSnapshotPrepareDiskExternalOverlayActive)
(qemuDomainSnapshotPrepareDiskExternalOverlayInactive)
(qemuDomainSnapshotPrepareDiskInternal)
(qemuDomainSnapshotPrepare)
(qemuDomainSnapshotCreateSingleDiskActive): Likewise.
* src/qemu/qemu_hotplug.c (qemuDomainChangeEjectableMedia):
Likewise.
* src/qemu/qemu_migration.c (qemuMigrationIsSafe): Likewise.
* src/security/security_apparmor.c
(AppArmorRestoreSecurityImageLabel)
(AppArmorSetSecurityImageLabel): Likewise.
* src/security/security_dac.c (virSecurityDACSetSecurityImageLabel)
(virSecurityDACRestoreSecurityImageLabelInt)
(virSecurityDACSetSecurityAllLabel): Likewise.
* src/security/security_selinux.c
(virSecuritySELinuxRestoreSecurityImageLabelInt)
(virSecuritySELinuxSetSecurityImageLabel)
(virSecuritySELinuxSetSecurityAllLabel): Likewise.
* src/storage/storage_backend.c (virStorageFileBackendForType):
Likewise.
* src/storage/storage_backend_fs.c (virStorageFileBackendFile)
(virStorageFileBackendBlock): Likewise.
* src/storage/storage_backend_gluster.c
(virStorageFileBackendGluster): Likewise.
* src/vbox/vbox_tmpl.c (vboxDomainGetXMLDesc, vboxAttachDrives)
(vboxDomainAttachDeviceImpl, vboxDomainDetachDevice): Likewise.
* src/vmware/vmware_conf.c (vmwareVmxPath): Likewise.
* src/vmx/vmx.c (virVMXParseDisk, virVMXFormatDisk)
(virVMXFormatFloppy): Likewise.
* src/xenxs/xen_sxpr.c (xenParseSxprDisks, xenParseSxpr)
(xenFormatSxprDisk): Likewise.
* src/xenxs/xen_xm.c (xenParseXM, xenFormatXMDisk): Likewise.
* tests/securityselinuxlabeltest.c (testSELinuxLoadDef):
Likewise.
* src/libvirt_private.syms (domain_conf.h): Move symbols...
(virstoragefile.h): ...as appropriate.
Signed-off-by: NEric Blake <eblake@redhat.com>

Part of a series of cleanups to use new accessor methods.

* src/qemu/qemu_conf.c (qemuCheckSharedDevice)
(qemuAddSharedDevice, qemuRemoveSharedDevice, qemuSetUnprivSGIO):
Use accessors.
* src/qemu/qemu_domain.c (qemuDomainDeviceDefPostParse)
(qemuDomainObjCheckDiskTaint, qemuDomainSnapshotForEachQcow2Raw)
(qemuDomainCheckRemoveOptionalDisk, qemuDomainCheckDiskPresence)
(qemuDiskChainCheckBroken, qemuDomainDetermineDiskChain):
Likewise.
* src/qemu/qemu_hotplug.c (qemuDomainChangeEjectableMedia)
(qemuDomainCheckEjectableMedia)
(qemuDomainAttachVirtioDiskDevice, qemuDomainAttachSCSIDisk)
(qemuDomainAttachUSBMassstorageDevice)
(qemuDomainAttachDeviceDiskLive, qemuDomainRemoveDiskDevice)
(qemuDomainDetachVirtioDiskDevice, qemuDomainDetachDiskDevice):
Likewise.
* src/qemu/qemu_migration.c (qemuMigrationStartNBDServer)
(qemuMigrationDriveMirror, qemuMigrationCancelDriveMirror)
(qemuMigrationIsSafe): Likewise.
* src/qemu/qemu_process.c (qemuProcessGetVolumeQcowPassphrase)
(qemuProcessHandleIOError, qemuProcessHandleBlockJob)
(qemuProcessInitPasswords): Likewise.
* src/qemu/qemu_driver.c (qemuDomainChangeDiskMediaLive)
(qemuDomainGetBlockInfo, qemuDiskPathToAlias): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

It's easy to shed the daemon these days. With this XML snippet:

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/some/dummy/path/test.bin'>
        <seclabel model='dac' relabel='no'/>
      </source>
      <target dev='vdb' bus='virtio'/>
      <readonly/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>

I get the SIGSEGV when starting the domain. The thing is, when
starting a domain, we check for its disk presence. For some reason,
when determining the disk chain, we parse the <seclabel/> (don't ask
me why). However, there's no label attribute in the XML, so we end up
calling virParseOwnershipIds() over NULL string:

 [Switching to Thread 0x7ffff10c4700 (LWP 30956)]
 __strchr_sse42 () at ../sysdeps/x86_64/multiarch/strchr.S:136
 136     ../sysdeps/x86_64/multiarch/strchr.S: No such file or directory.
 (gdb) bt
 #0  __strchr_sse42 () at ../sysdeps/x86_64/multiarch/strchr.S:136
 #1  0x00007ffff749f800 in virParseOwnershipIds (label=0x0, uidPtr=uidPtr@entry=0x7ffff10c2df0, gidPtr=gidPtr@entry=0x7ffff10c2df4) at util/virutil.c:2115
 #2  0x00007fffe929f006 in qemuDomainGetImageIds (gid=0x7ffff10c2df4, uid=0x7ffff10c2df0, disk=0x7fffe40cb000, vm=0x7fffe40a6410, cfg=0x7fffe409ae00) at qemu/qemu_domain.c:2385
 #3  qemuDomainDetermineDiskChain (driver=driver@entry=0x7fffe40120e0, vm=vm@entry=0x7fffe40a6410, disk=disk@entry=0x7fffe40cb000, force=force@entry=false) at qemu/qemu_domain.c:2414
 #4  0x00007fffe929f128 in qemuDomainCheckDiskPresence (driver=driver@entry=0x7fffe40120e0, vm=vm@entry=0x7fffe40a6410, cold_boot=cold_boot@entry=true) at qemu/qemu_domain.c:2250
 #5  0x00007fffe92b6fc8 in qemuProcessStart (conn=conn@entry=0x7fffd4000b60, driver=driver@entry=0x7fffe40120e0, vm=vm@entry=0x7fffe40a6410, migrateFrom=migrateFrom@entry=0x0, stdin_fd=stdin_fd@entry=-1, stdin_path=stdin_path@entry=0x0, snapshot=snapshot@entry=0x0,
     vmop=vmop@entry=VIR_NETDEV_VPORT_PROFILE_OP_CREATE, flags=flags@entry=1) at qemu/qemu_process.c:3813
 #6  0x00007fffe93087e8 in qemuDomainObjStart (conn=0x7fffd4000b60, driver=driver@entry=0x7fffe40120e0, vm=vm@entry=0x7fffe40a6410, flags=flags@entry=0) at qemu/qemu_driver.c:6051
 #7  0x00007fffe9308e32 in qemuDomainCreateWithFlags (dom=0x7fffcc000d50, flags=0) at qemu/qemu_driver.c:6105
 #8  0x00007ffff753c5cc in virDomainCreate (domain=domain@entry=0x7fffcc000d50) at libvirt.c:8861
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

Any source file which calls the logging APIs now needs
to have a VIR_LOG_INIT("source.name") declaration at
the start of the file. This provides a static variable
of the virLogSource type.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Eliminate all the code re-use which checks for priv->agentError or
priv->agent.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

Many of the domain xml format functions (including all of the device
format functions) had hard-coded spaces, which made for incorrect
indentation when those functions were called in a different context
(for example, commit 2122cf39 added <interface> XML into the document
provided to a network hook script, and in this case it should have
been indented by 2 spaces, but was instead indented by 6 spaces).

To make it possible to insert a properly indented device anywhere into
an XML document, this patch removes hardcoded spaces from the
formatting functions, and calls virBufferAdjustIndent() at appropriate
places instead. (a regex search of domain_conf.c was done to assure
that all occurrences of hardcoded spaces were removed).

virDomainDiskSourceDefFormatInternal() is also called from
snapshot_conf.c, so two virBufferAdjustIndent() calls were temporarily
added around that call - those functions will have hardcoded spaces
removed in a separate patch.

This could cause some conflicts when backporting future changes to the
formatting functions to older branches, but fortunately the changes
are almost all trivial, so conflict resolution will be obvious.

Some of these are leftovers from renaming the files, others
are just typos.

Also introduce an ugly awk script to enforce this.

This patch changes network device type used by default from rtl8139
to virtio when architecture type is aarch64 and machine type is virt.
Qemu doesn't support any other machine types for aarch64 right now and
we can't make any other aarch64-specific tuning in this function yet.
Signed-off-by: NOleg Strikov <oleg.strikov@canonical.com>

There is no keyboard working on PPC64 and PS2 mouse is only for X86
when graphics are enabled.

Add a USB keyboard and USB mouse for PPC64 when graphics are enabled.
Signed-off-by: NLi Zhang <zhlcindy@linux.vnet.ibm.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>

Currently, there's just one place where we care if hook script is
changing the domain XML: migration hook for incoming migration. In
all other places where a hook script is executed, we don't read the
XML back from the script.

Anyway, the hook script can alter domain XML and hence we should taint
it if the script did.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

The code took into account only the global permissions. The domains now
support per-vm DAC labels and per-image DAC labels. Use the most
specific label available.

AArch64 qemu has similar behavior as armv7l, like use of mmio etc.
This patch adds similar bypass checks what we have for armv7l to aarch64.
E.g. we are enabling mmio transport for Nicdev.
Making addDefaultUSB and addDefaultMemballoon to false etc.

V3:
- Adding missing domain rng schema for aarcg64 and test case in
  testutilsqemu.c which was causing test suite failure
  while running make check.

V2:
- Added testcase to qemuxml2argvtest as suggested
  during review comments of V1.

V1:
- Initial patch.
Signed-off-by: NAnup Patel <anup.patel@linaro.org>
Signed-off-by: NPranavkumar Sawargaonkar <pranavkumar@linaro.org>

The virDomainEvent class is kept as it indicates what meta informations
are valid for the children classes. This may be useful in the future.

Leave virDomainEventRegister and its Deregister brother as these are
legacy functions only for domain lifecycle events.

These changes allow the correct virtio-blk-device and virtio-net-device
devices to be used for the 'virt' machine type for armv7 rather than the
PCI virtio devices.

A test case was added to qemuxml2argvtest for this change.
Signed-off-by: NClark Laughlin <clark.laughlin@linaro.org>

In debugging a recent oVirt/libvirt race condition, I was very
frustrated by lack of logging in the job enter/exit code. This
patch adds some key data which would have been useful in by
debugging attempts.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The last argument of memmove is the amount of bytes to be moved. The
amount is in Bytes. We are moving some void pointers around. However,
since sizeof(void *) is not Byte on any architecture, we've got the
arithmetic wrong.

'const fooPtr' is the same as 'foo * const' (the pointer won't
change, but it's contents can).  But in general, if an interface
is trying to be const-correct, it should be using 'const foo *'
(the pointer is to data that can't be changed).

Fix up offenders in src/conf/domain_conf, and their fallout.

Several things to note: virObjectLock() requires a non-const
argument; if this were C++, we could treat the locking field
as 'mutable' and allow locking an otherwise 'const' object, but
that is a more invasive change, so I instead dropped attempts
to be const-correct on domain lookup.  virXMLPropString and
friends require a non-const xmlNodePtr - this is because libxml2
is not a const-correct library.  We could make the src/util/virxml
wrappers cast away const, but I figured it was easier to not
try to mark xmlNodePtr as const.  Finally, virDomainDeviceDefCopy
was a rather hard conversion - it calls virDomainDeviceDefPostParse,
which in turn in the xen driver was actually modifying the domain
outside of the current device being visited.  We should not be
adding a device on the first per-device callback, but waiting until
after all per-device callbacks are complete.

* src/conf/domain_conf.h (virDomainObjListFindByID)
(virDomainObjListFindByUUID, virDomainObjListFindByName)
(virDomainObjAssignDef, virDomainObjListAdd): Drop attempt at
const.
(virDomainDeviceDefCopy): Use intended type.
(virDomainDeviceDefParse, virDomainDeviceDefPostParseCallback)
(virDomainVideoDefaultType, virDomainVideoDefaultRAM)
(virDomainChrGetDomainPtrs): Make const-correct.
* src/conf/domain_conf.c (virDomainObjListFindByID)
(virDomainObjListFindByUUID, virDomainObjListFindByName)
(virDomainDeviceDefCopy, virDomainObjListAdd)
(virDomainObjAssignDef, virDomainHostdevSubsysUsbDefParseXML)
(virDomainHostdevSubsysPciOrigStatesDefParseXML)
(virDomainHostdevSubsysPciDefParseXML)
(virDomainHostdevSubsysScsiDefParseXML)
(virDomainControllerModelTypeFromString)
(virDomainTPMDefParseXML, virDomainTimerDefParseXML)
(virDomainSoundCodecDefParseXML, virDomainSoundDefParseXML)
(virDomainWatchdogDefParseXML, virDomainRNGDefParseXML)
(virDomainMemballoonDefParseXML, virDomainNVRAMDefParseXML)
(virSysinfoParseXML, virDomainVideoAccelDefParseXML)
(virDomainVideoDefParseXML, virDomainHostdevDefParseXML)
(virDomainRedirdevDefParseXML)
(virDomainRedirFilterUsbDevDefParseXML)
(virDomainRedirFilterDefParseXML, virDomainIdMapEntrySort)
(virDomainIdmapDefParseXML, virDomainVcpuPinDefParseXML)
(virDiskNameToBusDeviceIndex, virDomainDeviceDefCopy)
(virDomainVideoDefaultType, virDomainHostdevAssignAddress)
(virDomainDeviceDefPostParseInternal, virDomainDeviceDefPostParse)
(virDomainChrGetDomainPtrs, virDomainControllerSCSINextUnit)
(virDomainSCSIDriveAddressIsUsed)
(virDomainDriveAddressIsUsedByDisk)
(virDomainDriveAddressIsUsedByHostdev): Fix fallout.
* src/openvz/openvz_driver.c (openvzDomainDeviceDefPostParse):
Likewise.
* src/libxl/libxl_domain.c (libxlDomainDeviceDefPostParse):
Likewise.
* src/qemu/qemu_domain.c (qemuDomainDeviceDefPostParse)
(qemuDomainDefaultNetModel): Likewise.
* src/lxc/lxc_domain.c (virLXCDomainDeviceDefPostParse):
Likewise.
* src/uml/uml_driver.c (umlDomainDeviceDefPostParse): Likewise.
* src/xen/xen_driver.c (xenDomainDeviceDefPostParse): Split...
(xenDomainDefPostParse): ...since per-device callback is not the
time to be adding a device.
Signed-off-by: NEric Blake <eblake@redhat.com>

https://bugzilla.redhat.com/show_bug.cgi?id=994364

Whenever we check for ABI stability, we have new xml (e.g. provided by
user, or obtained from snapshot, whatever) which we compare to old xml
and see if ABI won't break. However, if the new xml was produced via
virDomainGetXMLDesc(..., VIR_DOMAIN_XML_MIGRATABLE) it lacks some
devices, e.g. 'pci-root' controller. Hence, the ABI stability check
fails even though it is stable. Moreover, we can't simply fix
virDomainDefCheckABIStability because removing the correct devices is
task for the driver. For instance, qemu driver wants to remove the usb
controller too, while LXC driver doesn't. That's why we need special
qemu wrapper over virDomainDefCheckABIStability which removes the
correct devices from domain XML, produces MIGRATABLE xml and calls the
check ABI stability function.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

If qemuParseCommandLine finds an arg it does not understand
it adds it to the QEMU passthrough custom arg list. If the
qemuParseCommandLine method hits an error for any reason
though, it just does 'VIR_FREE(cmd)' on the custom arg list.
This means all actual args / env vars are leaked. Introduce
a qemuDomainCmdlineDefFree method to be used for cleanup.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The VIR_FREE() macro will cast away any const-ness. This masked a
number of places where we passed a 'const char *' string to
VIR_FREE. Fortunately in all of these cases, the variable was not
in fact const data, but a heap allocated string. Fix all the
variable declarations to reflect this.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Similar to the chardev bit, ARM boards depend on the old style '-net nic'
for actually instantiating net devices. But we can't block out
-netdev altogether since it's needed for upcoming virtio support.

And add tests for working ARM XML with console, disk, and networking.

And add test cases for a basic working ARM guest.

This should be a no-op change for now.

This function is to guess the correct limit for maximal memory
usage by qemu for given domain. This can never be guessed
correctly, not to mention all the pains and sleepless nights this
code has caused. Once somebody discovers algorithm to solve the
Halting Problem, we can compute the limit algorithmically. But
till then, this code should never see the light of the release
again.

Go through disks of guest, if one disk doesn't exist or its backing
chain is broken, with 'optional' startupPolicy, for CDROM and Floppy
we only discard its source path definition in xml, for disks we drop
it from disk list and free it.

This patch adds in special handling for a few devices that need to be
treated differently for q35 domains:

usb - there is no implicit/default usb controller for the q35
machinetype. This is done because normally the default usb controller
is added to a domain by just adding "-usb" to the qemu commandline,
and it's assumed that this will add a single piix3 usb1 controller at
slot 1 function 2. That's not what happens when the machinetype is
q35, though. Instead, adding -usb to the commandline adds 3 usb
(version 2) controllers to the domain at slot 0x1D.{1,2,7}. Rather
than having

  <controller type='usb' index='0'/>

translate into 3 separate devices on the PCI bus, it's cleaner to not
automatically add a default usb device; one can always be added
explicitly if desired. Or we may decide that on q35 machines, 3 usb
controllers will be automatically added when none is given. But for
this initial commit, at least we aren't locking ourselves into
something we later won't want.

video - qemu always initializes the primary video device immediately
after any integrated devices for the machinetype. Unless instructed
otherwise (by using "-device vga..." instead of "-vga" which libvirt
uses in many cases to work around deficiencies and bugs in various
qemu versions) qemu will always pick the first unused slot. In the
case of the "pc" machinetype and its derivatives, this is always slot
2, but on q35 machinetypes, the first free slot is slot 1 (since the
q35's integrated peripheral devices are placed in other slots,
e.g. slot 0x1f). In order to make the PCI address of the video device
predictable, that slot (1 or 2, depending on machinetype) is reserved
even when no video device has been specified.

sata - a q35 machine always has a sata controller implicitly added at
slot 0x1F, function 2. There is no way to avoid this controller, so we
always add it. Note that the xml2xml tests for the pcie-root and q35
cases were changed to use DO_TEST_DIFFERENT() so that we can check for
the sata controller being automatically added. This is especially
important because we can't check for it in the xml2argv output (it has
no effect on that output since it's an implicit device).

ide - q35 has no ide controllers.

isa and smbus controllers - these two are always present in a q35 (at
slot 0x1F functions 0 and 3) but we have no way of modelling them in
our config. We do need to reserve those functions so that the user
doesn't attempt to put anything else there though. (note that the "pc"
machine type also has an ISA controller, which we also ignore).

This PCI controller, named "dmi-to-pci-bridge" in the libvirt config,
and implemented with qemu's "i82801b11-bridge" device, connects to a
PCI Express slot (e.g. one of the slots provided by the pcie-root
controller, aka "pcie.0" on the qemu commandline), and provides 31
*non-hot-pluggable* PCI (*not* PCIe) slots, numbered 1-31.

Any time a machine is defined which has a pcie-root controller
(i.e. any q35-based machinetype), libvirt will automatically add a
dmi-to-pci-bridge controller if one doesn't exist, and also add a
pci-bridge controller. The reasoning here is that any useful domain
will have either an immediate (startup time) or eventual (subsequent
hot-plug) need for a standard PCI slot; since the pcie-root controller
only provides PCIe slots, we need to connect a dmi-to-pci-bridge
controller to it in order to get a non-hot-plug PCI slot that we can
then use to connect a pci-bridge - the slots provided by the
pci-bridge will be both standard PCI and hot-pluggable.

Since pci-bridge devices themselves can not be hot-plugged into a
running system (although you can hot-plug other devices into a
pci-bridge's slots), any new pci-bridge controller that is added can
(and will) be plugged into the dmi-to-pci-bridge as long as it has
empty slots available.

This patch is also changing the qemuxml2xml-pcie test from a "DO_TEST"
to a "DO_DIFFERENT_TEST". This is so that the "before" xml can omit
the automatically added dmi-to-pci-bridge and pci-bridge devices, and
the "after" xml can include it - this way we are testing if libvirt is
properly adding these devices.

This controller is implicit on q35 machinetypes. It provides 31 PCIe
(*not* PCI) slots as controller 0.

Currently there are no devices that can connect to pcie-root, and no
implicit pci controller on a q35 machine, so q35 is still
unusable. For a usable q35 system, we need to add a
"dmi-to-pci-bridge" pci controller, which can connect to pcie-root,
and provides standard pci slots that can be used to connect other
devices.

The parser shouldn't be doing arch-specific things like adding in
implicit controllers to the config. This should instead be done in the
hypervisor's post-parse callback.

This patch removes the auto-add of a usb controller from the domain
parser, and puts it into the qemu driver's post-parse callback (just
as is already done with the auto-add of the pci-root controller). In
the future, any machine/arch that shouldn't have a default usb
controller added should just set addDefaultUSB = false in this
function.

We've recently seen that q35 and ARMV7L domains shouldn't get a default USB
controller, so I've set addDefaultUSB to false for both of those.

For disk with startupPolicy support, such as cdrom and floppy
when its chain is broken, the startup policy will apply,
otherwise, report an error.

*src/util/virstoragefile.c: Add a helper function to get
the first name of missing backing files, if the name is NULL,
it means the diskchain is not broken.
*src/qemu/qemu_domain.c: qemuDiskChainCheckBroken(disk) to
check if its chain is broken