Extending the iothread disk support from pci to pci and ccw.
Signed-off-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Reviewed-by: Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
This patch adds parsing/formatting code as well as documentation for
shared memory devices. This will currently be only accessible in QEMU
using it's ivshmem device, but is designed as generic as possible to
allow future expansion for other hypervisors.
In the devices section in the domain XML users may specify:
- For shmem device using a server:
<shmem name='shmem0'>
<server path='/tmp/socket-ivshmem0'/>
<size unit='M'>32</size>
<msi vectors='32' ioeventfd='on'/>
</shmem>
- For ivshmem device not using an ivshmem server:
<shmem name='shmem1'>
<size unit='M'>32</size>
</shmem>
Most of the configuration is made optional so it also allows
specifications like:
<shmem name='shmem1/>
<shmem name='shmem2'>
<server/>
</shmem>
Signed-off-by: Maxime Leroy <maxime.leroy@6wind.com>
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Add options for tuning segment offloading:
<driver>
<host csum='off' gso='off' tso4='off' tso6='off'
ecn='off' ufo='off'/>
<guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/>
</driver>
which control the respective host_ and guest_ properties
of the virtio-net device.
For tuning the network, alternative devices
for creating tap and vhost devices can be specified via:
<backend tap='/dev/net/tun' vhost='/dev/net-vhost'/>
I noticed this with the recent iothread pinning code, but the
problem existed longer than that. The XML validation required
users to supply <cputune> children in a strict order, even though
there was no conceptual reason why they can't occur in any order.
docs/ changes best viewed with -w
* docs/schemas/domaincommon.rng (cputune): Add interleave.
* tests/qemuxml2argvdata/qemuxml2argv-cputune-iothreads.xml: Swap
up order, copying canonical form...
* tests/qemuxml2xmloutdata/qemuxml2xmlout-cputune-iothreads.xml:
...here.
* tests/qemuxml2xmltest.c (mymain): Mark the difference.
Signed-off-by: Eric Blake <eblake@redhat.com>
https://bugzilla.redhat.com/show_bug.cgi?id=1101574
Add an option 'iothreadpin' to the <cpuset> to allow for setting the
CPU affinity for each IOThread.
The iothreadspin will mimic the vcpupin with respect to being able to
assign each iothread to a specific CPU, although iothreads ids start
at 1 while vcpu ids start at 0. This matches the iothread naming scheme.
Up to now, users can configure BIOS via the <loader/> element. With
the upcoming implementation of UEFI this is not enough as BIOS and
UEFI are conceptually different. For instance, while BIOS is ROM, UEFI
is programmable flash (although all writes to code section are
denied). Therefore we need new attribute @type which will
differentiate the two. Then, new attribute @readonly is introduced to
reflect the fact that some images are RO.
Moreover, the OVMF (which is going to be used mostly), works in two
modes:
1) Code and UEFI variable store is mixed in one file.
2) Code and UEFI variable store is separated in two files
The latter has advantage of updating the UEFI code without losing the
configuration. However, in order to represent the latter case we need
yet another XML element: <nvram/>. Currently, it has no additional
attributes, it's just a bare element containing path to the variable
store file.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This commit is rather big. Firstly, the in memory config
representation is adjusted like if security_driver was set to "none".
The rest is then just adaptation to the new code that will generate
different seclabels.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
For virtio-blk-pci disks with the disk iothread attribute that are
running the correct emulator, add the "iothread=iothread#" to the
-device command line in order to enable iothreads for the disk as
long as the command is available, the disk iothread value provided is
valid, and is supported for the disk device being added
Add a new capability to ensure the iothreads feature exists for the qemu
emulator being run - requires the "query-iothreads" QMP command. Using the
domain XML add correspoding command argument in order to generate the
threads. The iothreads will use a name space "iothread#" where, the
future patch to add support for using an iothread to a disk definition to
merely define which of the available threads to use.
Add tests to ensure the xml/argv processing is correct. Note that no
change was made to qemuargv2xmltest.c as processing the -object element
would require knowing more than just iothreads.
QEMU 2.1 added support for the kvm=off option to the -cpu command,
allowing the KVM hypervisor signature to be hidden from the guest.
This enables disabling of some paravirualization features in the
guest as well as allowing certain drivers which test for the
hypervisor to load. Domain XML syntax is as follows:
<domain type='kvm>
...
<features>
...
<kvm>
<hidden state='on'/>
</kvm>
</features>
...
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
https://bugzilla.redhat.com/show_bug.cgi?id=1128751
There's this <driver/> element under <interface/> which can have
several attributes. However, the driver element is currently formated
only if the driver's name or txmode has been specified. This makes
only a little sense as we parse even partial <driver/>, for instance:
<interface type='user'>
<mac address='52:54:00:e5:48:58'/>
<model type='virtio'/>
<driver ioeventfd='on' event_idx='on' queues='5'/>
</interface>
But such XML would never get formatted back.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Introduce a new structure to handle an iSCSI host device based on the
existing virDomainHostdevSubsysSCSI by adding a "protocol='iscsi'" to
the <source/> element. The existing scsi_host subsystem RNG was modified
to read an optional "protocol='adapter'", although it won't be written
out nor is it documented as an option (by choice).
The new hostdev structure mimics the existing <disk/> element for an
iSCSI device (network) device. New XML is:
<hostdev mode='subsystem' type='scsi' managed='yes'>
<source protocol='iscsi' name='iqn.1992-01.com.example'>
<host name='example.org' port='3260'/>
<auth username='myname'>
<secret type='iscsi' usage='mycluster_myname'/>
</auth>
</source>
<address type='drive' controller='0' bus='0' target='2' unit='5'/>
</hostdev>
The controller element will mimic the existing scsi_host code insomuch
as when 'lsi' and 'virtio-scsi' are used.
A future patch is going to wire up qemu active block commit jobs;
but as they have similar events and are canceled/pivoted in the
same way as block copy jobs, it is easiest to track all bookkeeping
for the commit job by reusing the <mirror> element. This patch
adds domain XML to track which job was responsible for creating a
mirroring situation, and adds a job='copy' attribute to all
existing uses of <mirror>. Along the way, it also massages the
qemu monitor backend to read the new field in order to generate
the correct type of libvirt job (even though it requires a
future patch to actually cause a qemu event that can be reported
as an active commit). It also prepares to update persistent XML
to match changes made to live XML when a copy completes.
* docs/schemas/domaincommon.rng: Enhance schema.
* docs/formatdomain.html.in: Document it.
* src/conf/domain_conf.h (_virDomainDiskDef): Add a field.
* src/conf/domain_conf.c (virDomainBlockJobType): String conversion.
(virDomainDiskDefParseXML): Parse job type.
(virDomainDiskDefFormat): Output job type.
* src/qemu/qemu_process.c (qemuProcessHandleBlockJob): Distinguish
active from regular commit.
* src/qemu/qemu_driver.c (qemuDomainBlockCopy): Set job type.
(qemuDomainBlockPivot, qemuDomainBlockJobImpl): Clean up job type
on completion.
* tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-mirror-old.xml:
Update tests.
* tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml: Likewise.
* tests/qemuxml2argvdata/qemuxml2argv-disk-active-commit.xml: New
file.
* tests/qemuxml2xmltest.c (mymain): Drive new test.
Signed-off-by: Eric Blake <eblake@redhat.com>
There were numerous places where numatune configuration (and thus
domain config as well) was changed in different ways. On some
places this even resulted in persistent domain definition not to be
stable (it would change with daemon's restart).
In order to uniformly change how numatune config is dealt with, all
the internals are now accessible directly only in numatune_conf.c and
outside this file accessors must be used.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
In XML format, by definition, order of fields should not matter, so
order of parsing the elements doesn't affect the end result. When
specifying guest NUMA cells, we depend only on the order of the 'cell'
elements. With this patch all older domain XMLs are parsed as before,
but with the 'id' attribute they are parsed and formatted according to
that field. This will be useful when we have tuning settings for
particular guest NUMA node.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
This patch adds support for the QEMU vhost-user feature to libvirt.
vhost-user enables the communication between a QEMU virtual machine
and other userspace process using the Virtio transport protocol.
It uses a char dev (e.g. Unix socket) for the control plane,
while the data plane based on shared memory.
The XML looks like:
<interface type='vhostuser'>
<mac address='52:54:00:3b:83:1a'/>
<source type='unix' path='/tmp/vhost.sock' mode='server'/>
<model type='virtio'/>
</interface>
Signed-off-by: Michele Paolino <m.paolino@virtualopensystems.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
https://bugzilla.redhat.com/show_bug.cgi?id=1113860
We've always done that. Well, until 990e46c45. Point is, if we don't
format model, we may lose a domain on libvirtd restart. If the
seclabel is implicit however, we should skip it's formatting.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This introduces two new attributes "cmd_per_lun" and "max_sectors" same
with the names QEMU uses for virtio-scsi. An example of the XML:
<controller type='scsi' index='0' model='virtio-scsi' cmd_per_lun='50'
max_sectors='512'/>
The corresponding QEMU command line:
-device virtio-scsi-pci,id=scsi0,cmd_per_lun=50,max_sectors=512,
bus=pci.0,addr=0x3
Signed-off-by: Mike Perez <thingee@gmail.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>
Now that we track a disk mirror as a virStorageSource, we might
as well update the XML to theoretically allow any type of
mirroring destination (not just a local file). A later patch
will also be reusing <mirror> to track the block commit of the
top layer of a chain, which is another case where libvirt needs
to update the backing chain after the job is finally pivoted,
and since backing chains can have network backing files as the
destination to commit into, it makes more sense to display that
in the XML.
This patch changes output-only XML; it was already documented
that <mirror> does not affect a domain definition at this point
(because qemu doesn't provide persistent bitmaps yet). Any
application that was starting a block copy job with older libvirt
and then relying on the domain XML to determine if it was
complete will no longer be able to access the file= and format=
attributes of mirror that were previously used. However, this is
not going to be a problem in practice: the only time a block copy
job works is on a transient domain, and any app that is managing
a transient domain probably already does enough of its own
bookkeeping to know which file it is mirroring into without
having to re-read it from the libvirt XML. The one thing that
was likely to be used in a mirroring job was the ready=
attribute, which is unchanged. Meanwhile, I made sure the schema
and parser still accept the old format, even if we no longer
output it, so that upgrading from an older version of libvirt is
seamless.
* docs/schemas/domaincommon.rng (diskMirror): Alter definition.
* src/conf/domain_conf.c (virDomainDiskDefParseXML): Parse two
styles of mirror elements.
(virDomainDiskDefFormat): Output new style.
* tests/qemuxml2argvdata/qemuxml2argv-disk-mirror-old.xml: New
file, copied from...
* tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml: ...here
before modernizing.
* tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-mirror-old*: New
files.
* tests/qemuxml2xmltest.c (mymain): Test both styles.
Signed-off-by: Eric Blake <eblake@redhat.com>
We allow a seclabel to be specified in the <source> element
of a chardev:
<serial type='file'>
<source path='/tmp/serial.file'>
<seclabel model='dac' relabel='no'/>
</source>
</serial>
But we format it outside the source:
<serial type='file'>
<source path='/tmp/serial.file'/>
<target port='0'/>
<seclabel model='dac' relabel='no'/>
</serial>
Move the formatting inside the source to fix this to make the
seclabel persistent across XML format->parse.
Introduced by commit f8b08d0 'Add <seclabel> to character devices.'
So far, qemuxml2xml test was only able to check if the result matches
the original or the appropriate XML in qemuxml2xmloutdata regardless on
flags used to format the XML. Since the result can be different
depending on VIR_DOMAIN_XML_INACTIVE flag being used or not, this patch
adds support for qemuxml2xmlout-%s-active.xml and
qemuxml2xmlout-%s-inactive.xml output files. If the file specific to the
flag used exists, it is used in preference to the generic
qemuxml2xmlout-%s.xml file when reading the expected output.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
I noticed that depending on the <driver> attributes the user passed
in, the output may omit the <driver> element altogether. For example,
the rerror_policy has had this problem since commit 4bb4109 in Oct
2011. But in adding testsuite coverage to expose it, I found another
problem: the C code is just fine without a driver name, but the
XML validator required either a name or a cache mode.
* src/conf/domain_conf.c (virDomainDiskDefFormat): Update
conditional.
* docs/schemas/domaincommon.rng (diskDriver): Simplify.
* tests/qemuxml2argvdata/qemuxml2argv-disk-drive-copy-on-read.xml:
* tests/qemuxml2argvdata/qemuxml2argv-disk-drive-copy-on-read.args:
New files.
* tests/qemuxml2argvdata/qemuxml2argv-disk-drive-discard.xml:
Enhance test.
* tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-discard.xml:
Likewise.
* tests/qemuxml2argvtest.c (mymain): New test.
* tests/qemuxml2xmltest.c (mymain): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
In general, we try to make virt-xml-validate tolerant of input
elements in any order when possible. However, as written, the
RNG grammar did not permit <source> unless there was an explicit
type= attribute (even though the C code manages just fine by
defaulting to type='file'). After making the attribute optional
on the 'file' branch, I noticed that the use of diskspec was now
redundant with the branch when no <source> was supplied.
View this patch with 'git diff -b' for a better picture of the
schema change.
* docs/schemas/domaincommon.rng (disk): Hoist 'diskspec' out of
choice, make type='file' default, and still preserve interleave.
* tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-source-pool.xml:
* tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-discard.xml:
New files.
* tests/qemuxml2argvdata/qemuxml2argv-disk-source-pool.xml:
* tests/qemuxml2argvdata/qemuxml2argv-disk-drive-discard.xml:
Reorder XML.
* tests/qemuxml2xmltest.c (mymain): Cover new files.
Signed-off-by: Eric Blake <eblake@redhat.com>
Currently, <cputune><shares>0</shares></cputune> is treated
as if it were not specified.
Treat is as a valid value if it was explicitly specified
and write it to the cgroups.
Commit a1cbe4b5 added a check for spaces around assignments and this
patch extends it to checks for spaces around '=='. One exception is
virAssertCmpInt where comma after '==' is acceptable (since it is a
macro and '==' is its argument).
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Add a new backend for any character device. This backend uses channel
in spice connection. This channel is similar to spicevmc, but
all-purpose in contrast to spicevmc.
Apart from spicevmc, spiceport-backed chardev will not be formatted
into the command-line if there is no spice to use (with test for that
as well). For this I moved the def->graphics counting to the start
of the function so its results can be used in rest of the code even in
the future.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Add a new <timer> for the HyperV reference time counter enlightenment
and the iTSC reference page for Windows guests.
This feature provides a paravirtual approach to track timer events for
the guest (similar to kvmclock) with the option to use real hardware
clock on systems with a iTSC with compensation across various hosts.
According to the documentation describing various tunables for domain
timers not all the fields are supported by all the driver types. Express
these in the RNG:
- rtc, platform: Only these support the "track" attribute.
- tsc: only one to support "frequency" and "mode" attributes
- hpet, pit: tickpolicy/catchup attribute/element
- kvmclock: no extra attributes are supported
Additionally the attributes of the <catchup> element for
tickpolicy='catchup' are optional according to the parsing code. Express
this in the XML and fix a spurious space added while formatting the
<catchup> element and add tests for it.
Any test suite which involves a virDomainDefPtr should
call virDomainDefCheckABIStability with itself just as
a basic sanity check that the identity-comparison always
succeeds. This would have caught the recent NULL pointer
access crash.
Make sure we cope with def->name being NULL since the
VMWare config parser produces NULL names.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Map the new <panic> device in XML to the '-device pvpanic' command
line of qemu. Clients can then couple the <panic> device and the
<on_crash> directive to control behavior when the guest reports
a panic to qemu.
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
When changing memtune limits to unlimited with AFFECT_CONFIG, the
values in virDomainDef are set to PARAM_UNLIMITED, which causes the
whole <memtune> to be formatted. This can be changed in all drivers,
but it also makes sense to use the default (0) as another value for
"unlimited", since zero memory limit makes no sense.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
https://bugzilla.redhat.com/show_bug.cgi?id=1027096
If there's the following snippet in the domain XML, the domain will be
lost upon the daemon restart (if the domain is started prior restart):
<seclabel type='dynamic' relabel='yes'/>
The problem is, the 'label', 'imagelabel' and 'baselabel' are parsed
whenever the VIR_DOMAIN_XML_INACTIVE is *not* present or the label is
static. The latter is not our case, obviously. So, when libvirtd starts
up, it finds domain state xml and parse it. During parsing, many XML
flags are enabled but VIR_DOMAIN_XML_INACTIVE. Hence, our parser tries
to extract 'label', 'imagelabel' and 'baselabel' from the XML which
fails for model='none'. Err, this model - even though not specified in
XML - can be taken from qemu wide config file: /etc/libvirtd/qemu.conf.
However, in order to know we are dealing with model='none' the code in
question must be moved forward a bit. Then a new check must be
introduced. This is what the first two chunks are doing.
But this alone is not sufficient. The domain state XML won't contain the
model attribute without slight modification. The model should be
inserted into the XML even if equal to 'none' and the state XML is being
generated - what if the origin (the @security_driver variable in
qemu.conf) changes during libvirtd restarts?
At the end, a test to catch this scenario is introduced.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
The linux kernel recently added support for paravirtual spinlock
handling to avoid performance regressions on overcomitted hosts. This
feature needs to be turned in the hypervisor so that the guest OS is
notified about the possible support.
This patch adds a new feature "paravirt-spinlock" to the XML and
supporting code to enable the "kvm_pv_unhalt" pseudo CPU feature in
qemu.
https://bugzilla.redhat.com/show_bug.cgi?id=1008989
The test case average timing code has not been used by any test
case ever. Delete it to remove complexity.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
The qemuxml2xmltest.c function testCompareXMLToXMLHelper would
clobber the 'ret' variable causing it to mis-diagnose OOM
errors.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
<controller type='pci' index='0' model='pci-root'>
<pcihole64 unit='KiB'>1048576</pcihole64>
</controller>
It can be used to adjust (or disable) the size of the 64-bit
PCI hole. The size attribute is in kilobytes (different unit
can be specified on input), but it gets rounded up to
the nearest GB by QEMU.
Disabling it will be needed for guests that crash with the
64-bit PCI hole (like Windows XP), see:
https://bugzilla.redhat.com/show_bug.cgi?id=990418
https://bugzilla.redhat.com/show_bug.cgi?id=924153
Commit 904e05a2 (v0.9.9) added a per-<disk> seclabel element with
an attribute relabel='no' in order to try and minimize the
impact of shutdown delays when an NFS server disappears. The idea
was that if a disk is on NFS and can't be labeled in the first
place, there is no need to attempt the (no-op) relabel on domain
shutdown. Unfortunately, the way this was implemented was by
modifying the domain XML so that the optimization would survive
libvirtd restart, but in a way that is indistinguishable from an
explicit user setting. Furthermore, once the setting is turned
on, libvirt avoids attempts at labeling, even for operations like
snapshot or blockcopy where the chain is being extended or pivoted
onto non-NFS, where SELinux labeling is once again possible. As
a result, it was impossible to do a blockcopy to pivot from an
NFS image file onto a local file.
The solution is to separate the semantics of a chain that must
not be labeled (which the user can set even on persistent domains)
vs. the optimization of not attempting a relabel on cleanup (a
live-only annotation), and using only the user's explicit notation
rather than the optimization as the decision on whether to skip
a label attempt in the first place. When upgrading an older
libvirtd to a newer, an NFS volume will still attempt the relabel;
but as the avoidance of a relabel was only an optimization, this
shouldn't cause any problems.
In the ideal future, libvirt will eventually have XML describing
EVERY file in the backing chain, with each file having a separate
<seclabel> element. At that point, libvirt will be able to track
more closely which files need a relabel attempt at shutdown. But
until we reach that point, the single <seclabel> for the entire
<disk> chain is treated as a hint - when a chain has only one
file, then we know it is accurate; but if the chain has more than
one file, we have to attempt relabel in spite of the attribute,
in case part of the chain is local and SELinux mattered for that
portion of the chain.
* src/conf/domain_conf.h (_virSecurityDeviceLabelDef): Add new
member.
* src/conf/domain_conf.c (virSecurityDeviceLabelDefParseXML):
Parse it, for live images only.
(virSecurityDeviceLabelDefFormat): Output it.
(virDomainDiskDefParseXML, virDomainChrSourceDefParseXML)
(virDomainDiskSourceDefFormat, virDomainChrDefFormat)
(virDomainDiskDefFormat): Pass flags on through.
* src/security/security_selinux.c
(virSecuritySELinuxRestoreSecurityImageLabelInt): Honor labelskip
when possible.
(virSecuritySELinuxSetSecurityFileLabel): Set labelskip, not
norelabel, if labeling fails.
(virSecuritySELinuxSetFileconHelper): Fix indentation.
* docs/formatdomain.html.in (seclabel): Document new xml.
* docs/schemas/domaincommon.rng (devSeclabel): Allow it in RNG.
* tests/qemuxml2argvdata/qemuxml2argv-seclabel-*-labelskip.xml:
* tests/qemuxml2argvdata/qemuxml2argv-seclabel-*-labelskip.args:
* tests/qemuxml2xmloutdata/qemuxml2xmlout-seclabel-*-labelskip.xml:
New test files.
* tests/qemuxml2argvtest.c (mymain): Run the new tests.
* tests/qemuxml2xmltest.c (mymain): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
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).
