Our test data used a lot of different qemu binary paths and some
of them were based on downstream systems.
Note that there is one file where I had to add "accel=kvm" because
the qemuargv2xml code parses "/usr/bin/kvm" as virt type="kvm".
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
The virt type for QEMU can be modified by -machine attribute "accel"
so there is no need to have different QEMU binary paths.
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Depending on the architecture, requirements for ACPI and UEFI can
be different; more specifically, while on x86 UEFI requires ACPI,
on aarch64 it's the other way around.
Enforce these requirements when validating the domain, and make
the error message more accurate by mentioning that they're not
necessarily applicable to all architectures.
Several aarch64 test cases had to be tweaked because they would
have failed the validation step otherwise.
We want pcie-root-ports to be used when available in QEMU,
but at the same time we need to ensure that hosts running
older QEMU releases keep working and that the user can
override the default at any time.
Add a comment for the original pcie-root-port test cases
to make it clear how these new test cases are different.
For NVDIMM devices it is optionally possible to specify the size
of internal storage for namespaces. Namespaces are a feature that
allows users to partition the NVDIMM for different uses.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Now that NVDIMM has found its way into libvirt, users might want
to fine tune some settings for each module separately. One such
setting is 'share=on|off' for the memory-backend-file object.
This setting - just like its name suggest already - enables
sharing the nvdimm module with other applications. Under the hood
it controls whether qemu mmaps() the file as MAP_PRIVATE or
MAP_SHARED.
Yet again, we have such config knob in domain XML, but it's just
an attribute to numa <cell/>. This does not give fine enough
tuning on per-memdevice basis so we need to have the attribute
for each device too.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
NVDIMM is new type of memory introduced into QEMU 2.6. The idea
is that we have a Non-Volatile memory module that keeps the data
persistent across domain reboots.
At the domain XML level, we already have some representation of
'dimm' modules. Long story short, NVDIMM will utilize the
existing <memory/> element that lives under <devices/> by adding
a new attribute 'nvdimm' to the existing @model and introduce a
new <path/> element for <source/> while reusing other fields. The
resulting XML would appear as:
<memory model='nvdimm'>
<source>
<path>/tmp/nvdimm</path>
</source>
<target>
<size unit='KiB'>523264</size>
<node>0</node>
</target>
<address type='dimm' slot='0'/>
</memory>
So far, this is just a XML parser/formatter extension. QEMU
driver implementation is in the next commit.
For more info on NVDIMM visit the following web page:
http://pmem.io/
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Up until a while ago, libvirt would automatically add a legacy
PCI controllers combo (dmi-to-pci-bridge + pci-bridge) to any
PCIe machine type (x86_64/q35 and aarch64/virt).
As a result, a number of input and output files in the test
suite ended up containing the legacy PCI controllers, even
though they are not needed or in any way relevant to the
feature being tested.
Get rid of most of the occurrences. Most of the time, this
just means removing the controllers from the input file and
regenerating the output files; in a few instances, some
minor tweaking is performed on the input file, most notably
removing the memory balloon: as memory balloon support was
not the scope of the test being changed, there is no loss
of test coverage from doing so.
Several occurrences of the legacy PCI controllers remain in
the test suite, both because removing their usage would have
required even more tweaking, and because we still want to
have coverage of this perfectly valid combination.
Add a new attribute 'rendernode' to <gl> spice element.
Give it to QEMU if qemu supports it (queued for 2.9).
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This part introduces new xml elements for file based
memorybacking support and their parsing.
(It allows vhost-user to be used without hugepages.)
New xml elements:
<memoryBacking>
<source type="file|anonymous"/>
<access mode="shared|private"/>
<allocation mode="immediate|ondemand"/>
</memoryBacking>
Not only we should set the MTU on the host end of the device but
also let qemu know what MTU did we set.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Based on work of Mehdi Abaakouk <sileht@sileht.net>.
When parsing vhost-user interface XML and no ifname is found we
can try to fill it in in post parse callback. The way this works
is we try to make up interface name from given socket path and
then ask openvswitch whether it knows the interface.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Set the VIR_PCI_CONNECT_AGGREGATE_SLOT flag for pcie-root-ports so
that they will be assigned to all the functions on a slot.
Some qemu test case outputs had to be adjusted due to the
pcie-root-ports now being put on multiple functions.
If there are multiple devices assigned to the different functions of a
single PCI slot, they will not work properly if the device at function
0 doesn't have its "multi" attribute turned on, so it makes sense for
libvirt to turn it on during PCI address assignment. Setting multi
then assures that the new setting is stored in the config (so it will
be used next time the domain is started), preventing any potential
problems in the case that a future change in the configuration
eliminates the devices on all non-0 functions (multi will still be set
for function 0 even though it is the only function in use on the slot,
which has no useful purpose, but also doesn't cause any problems).
(NB: If we were to instead just decide on the setting for
multifunction at runtime, a later removal of the non-0 functions of a
slot would result in a silent change in the guest ABI for the
remaining device on function 0 (although it may seem like an
inconsequential guest ABI change, it *is* a guest ABI change to turn
off the multi bit).)
virtio-pci is the way forward for aarch64 guests: it's faster
and less alien to people coming from other architectures.
Now that guest support is finally getting there (Fedora 24,
CentOS 7.3, Ubuntu 16.04 and Debian testing all support
virtio-pci out of the box), we'd like to start using it by
default instead of virtio-mmio.
Users and applications can already opt-in by explicitly using
<address type='pci'/>
inside the relevant elements, but that's kind of cumbersome and
requires all users and management applications to adapt, which
we'd really like to avoid.
What we can do instead is use virtio-mmio only if the guest
already has at least one virtio-mmio device, and use virtio-pci
in all other situations.
That means existing virtio-mmio guests will keep using the old
addressing scheme, and new guests will automatically be created
using virtio-pci instead. Users can still override the default
in either direction.
Existing tests such as aarch64-aavmf-virtio-mmio and
aarch64-virtio-pci-default already cover all possible
scenarios, so no additions to the test suites are necessary.
Since the great rework of how we store vcpu- and iothread-related
data, we have overly complex part of code that is trying to format the
scheduler tuning data in as less lines as possible by grouping
settings for multiple threads. That was designed as an input syntax
sugar for users, but we don't need to also use that when formatting
the XML. Switching to simple enumeration makes the code nicer,
shorter and more welcoming to future changes.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Modify _virDomainBlockIoTuneInfo and rng schema to support the group_name
option for iotune throttling. Document the new value.
Signed-off-by: John Ferlan <jferlan@redhat.com>
Don't use duplicate disk addresses in test cases unless it's useful. At
least the test case will break once we have a check for uniqueness of
addresses at time of domain definition.
Signed-off-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
With the QEMU components in place, provide the XML parsing to
invoke that code when given the following XML snippet:
<hostdev mode='subsystem' type='scsi_host'>
<source protocol='vhost' wwpn='naa.501234567890abcd'/>
</hostdev>
An optional address element can be specified within the hostdev
(pick CCW or PCI as necessary):
<address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0625'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
Add basic vhost-scsi tests which were cloned from hostdev-scsi-virtio-scsi
in both xml2argv and xml2xml. Added ones for both vhost-scsi-ccw and
vhost-scsi-pci since the syntaxes are slightly different between them.
Also adjusted the docs to describe the changes.
Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
For machinetypes with a pci-root bus (all legacy PCI), libvirt will
make a "fake" reservation for one extra slot prior to assigning
addresses to unaddressed PCI endpoint devices in the domain. This will
trigger auto-adding of a pci-bridge for the final device to be
assigned an address *if that device would have otherwise instead been
the last device on the last available pci-bridge*; thus it assures
that there will always be at least one slot left open in the domain's
bus topology for expansion (which is important both for hotplug (since
a new pci-bridge can't be added while the guest is running) as well as
for offline additions to the config (since adding a new device might
otherwise in some cases require re-addressing existing devices, which
we want to avoid)).
It's important to note that for the above case (legacy PCI), we must
check for the special case of all slots on all buses being occupied
*prior to assigning any addresses*, and avoid attempting to reserve
the extra address in that case, because there is no free address in
the existing topology, so no place to auto-add a pci-bridge for
expansion (i.e. it would always fail anyway). Since that condition can
only be reached by manual intervention, this is acceptable.
For machinetypes with pcie-root (Q35, aarch64 virt), libvirt's
methodology for automatically expanding the bus topology is different
- pcie-root-ports are plugged into slots (soon to be functions) of
pcie-root as needed, and the new endpoint devices are assigned to the
single slot in each pcie-root-port. This is done so that the devices
are, by default, hotpluggable (the slots of pcie-root don't support
hotplug, but the single slot of the pcie-root-port does). Since
pcie-root-ports can only be plugged into pcie-root, and we don't
auto-assign endpoint devices to the pcie-root slots, this means
topology expansion doesn't compete with endpoint devices for slots, so
we don't need to worry about checking for all "useful" slots being
free *prior* to assigning addresses to new endpoint devices - as a
matter of fact, if we attempt to reserve the open slots before the
used slots, it can lead to errors.
Instead this patch just reserves one slot for a "future potential"
PCIe device after doing the assignment for actual devices, but only
if the only PCI controller defined prior to starting address
assignment was pcie-root, and only if we auto-added at least one PCI
controller during address assignment. This assures two things:
1) that reserving the open slots will only be done when the domain is
initially defined, never at any time after, and
2) that if the user understands enough about PCI controllers that they
are adding them manually, that we don't mess up their plan by
adding extras - if they know enough to add one pcie-root-port, or
to manually assign addresses such that no pcie-root-ports are
needed, they know enough to add extra pcie-root-ports if they want
them (this could be called the "libguestfs clause", since
libguestfs needs to be able to create domains with as few
devices/controllers as possible).
This is set to reserve a single free port for now, but could be
increased in the future if public sentiment goes in that direction
(it's easy to increase later, but essentially impossible to decrease)
Real Q35 hardware has an ICH9 chip that includes several integrated
devices at particular addresses (see the file docs/q35-chipset.cfg in
the qemu source). libvirt already attempts to put the first two sets
of ich9 USB2 controllers it finds at 00:1D.* and 00:1A.* to match the
real hardware. This patch does the same for the ich9 "HD audio"
device.
The main inspiration for this patch is that currently the *only*
device in a reasonable "workstation" type virtual machine config that
requires a legacy PCI slot is the audio device, Without this patch,
the standard Q35 machine created by virt-manager will have a
dmi-to-pci-bridge and a pci-bridge just for the sound device; with the
patch (and if you change the sound device model from the default
"ich6" to "ich9"), the machine definition constructed by virt-manager
has absolutely no legacy PCI controllers - any legacy PCI devices
(e.g. video and sound) are on pcie-root as integrated devices.
Previously we added a set of EHCI+UHCI controllers to Q35 machines to
mimic real hardware as closely as possible, but recent discussions
have pointed out that the nec-usb-xhci (USB3) controller is much more
virtualization-friendly (uses less CPU), so this patch switches the
default for Q35 machinetypes to add an XHCI instead (if it's
supported, which it of course *will* be).
Since none of the existing test cases left out USB controllers in the
input XML, a new Q35 test case was added which has *no* devices, so
ends up with only the defaults always put in by qemu, plus those added
by libvirt.
Now the a dmi-to-pci-bridge is automatically added just as it's needed
(when a pci-bridge is being added), we no longer have any need to
force-add one to every single Q35 domain.
A few of the qemu test cases assume that a dmi-to-pci-bridge will
always be added at index 1, and so they omit it from the input data
even though a pci-bridge is present at index 2, e.g.:
<controller type='pci' index='0' model='pcie-root'/>
<controller type='pci' index='2' model='pci-bridge'/>
Support for this odd practice was discussed on libvir-list and we
decided that the complex code required to make this continue was not
worth the headache of maintaining. So instead, this patch modifies the
test cases to manually add a dmi-to-pci-bridge at index 1 (since an
upcoming patch is going to eliminate the unconditional adding of
dmi-to-pci-bridge).
Because the auto-add was placing the dmi-to-pci-bridge later in the
list (even though it has a lower index) the test output is also
updated to take account for the new order (which puts the pci
controllers in index-order)
Previously libvirt would only add pci-bridge devices automatically
when an address was requested for a device that required a legacy PCI
slot and none was available. This patch expands that support to
dmi-to-pci-bridge (which is needed in order to add a pci-bridge on a
machine with a pcie-root), and pcie-root-port (which is needed to add
a hotpluggable PCIe device). It does *not* automatically add
pcie-switch-upstream-ports or pcie-switch-downstream-ports (and
currently there are no plans for that).
Given the existing code to auto-add pci-bridge devices, automatically
adding pcie-root-ports is fairly straightforward. The
dmi-to-pci-bridge support is a bit tricky though, for a few reasons:
1) Although the only reason to add a dmi-to-pci-bridge is so that
there is a reasonable place to plug in a pci-bridge controller,
most of the time it's not the presence of a pci-bridge *in the
config* that triggers the requirement to add a dmi-to-pci-bridge.
Rather, it is the presence of a legacy-PCI device in the config,
which triggers auto-add of a pci-bridge, which triggers auto-add of
a dmi-to-pci-bridge (this is handled in
virDomainPCIAddressSetGrow() - if there's a request to add a
pci-bridge we'll check if there is a suitable bus to plug it into;
if not, we first add a dmi-to-pci-bridge).
2) Once there is already a single dmi-to-pci-bridge on the system,
there won't be a need for any more, even if it's full, as long as
there is a pci-bridge with an open slot - you can also plug
pci-bridges into existing pci-bridges. So we have to make sure we
don't add a dmi-to-pci-bridge unless there aren't any
dmi-to-pci-bridges *or* any pci-bridges.
3) Although it is strongly discouraged, it is legal for a pci-bridge
to be directly plugged into pcie-root, and we don't want to
auto-add a dmi-to-pci-bridge if there is already a pci-bridge
that's been forced directly into pcie-root.
Although libvirt will now automatically create a dmi-to-pci-bridge
when it's needed, the code still remains for now that forces a
dmi-to-pci-bridge on all domains with pcie-root (in
qemuDomainDefAddDefaultDevices()). That will be removed in a future
patch.
For now, the pcie-root-ports are added one to a slot, which is a bit
wasteful and means it will fail after 31 total PCIe devices (30 if
there are also some PCI devices), but helps keep the changeset down
for this patch. A future patch will have 8 pcie-root-ports sharing the
functions on a single slot.
The nec-usb-xhci device (which is a USB3 controller) has always
presented itself as a PCI device when plugged into a legacy PCI slot,
and a PCIe device when plugged into a PCIe slot, but libvirt has
always auto-assigned it to a legacy PCI slot.
This patch changes that behavior to auto-assign to a PCIe slot on
systems that have pcie-root (e.g. Q35 and aarch64/virt).
Since we don't yet auto-create pcie-*-port controllers on demand, this
means a config with an nec-xhci USB controller that has no PCI address
assigned will also need to have an otherwise-unused pcie-*-port
controller specified:
<controller type='pci' model='pcie-root-port'/>
<controller type='usb' model='nec-xhci'/>
(this assumes there is an otherwise-unused slot on pcie-root to accept
the pcie-root-port)
The e1000e is an emulated network device based on the Intel 82574,
present in qemu 2.7.0 and later. Among other differences from the
e1000, it presents itself as a PCIe device rather than legacy PCI. In
order to get it assigned to a PCIe controller, this patch updates the
flags setting for network devices when the model name is "e1000e".
(Note that for some reason libvirt has never validated the network
device model names other than to check that there are no dangerous
characters in them. That should probably change, but is the subject of
another patch.)
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1343094
libvirt previously assigned nearly all devices to a "hotpluggable"
legacy PCI slot even on machines with a PCIe root bus (and even though
most such machines don't even support hotplug on legacy PCI slots!)
Forcing all devices onto legacy PCI slots means that the domain will
need a dmi-to-pci-bridge (to convert from PCIe to legacy PCI) and a
pci-bridge (to provide hotpluggable legacy PCI slots which, again,
usually aren't hotpluggable anyway).
To help reduce the need for these legacy controllers, this patch tries
to assign virtio-1.0-capable devices to PCIe slots whenever possible,
by setting appropriate connectFlags in
virDomainCalculateDevicePCIConnectFlags(). Happily, when that function
was written (just a few commits ago) it was created with a
"virtioFlags" argument, set by both of its callers, which is the
proper connectFlags to set for any virtio-*-pci device - depending on
the arch/machinetype of the domain, and whether or not the qemu binary
supports virtio-1.0, that flag will have either been set to PCI or
PCIe. This patch merely enables the functionality by setting the flags
for the device to whatever is in virtioFlags if the device is a
virtio-*-pci device.
NB: the first virtio video device will be placed directly on bus 0
slot 1 rather than on a pcie-root-port due to the override for primary
video devices in qemuDomainValidateDevicePCISlotsQ35(). Whether or not
to change that is a topic of discussion, but this patch doesn't change
that particular behavior.
NB2: since the slot must be hotpluggable, and pcie-root (the PCIe root
complex) does *not* support hotplug, this means that suitable
controllers must also be in the config (i.e. either pcie-root-port, or
pcie-downstream-port). For now, libvirt doesn't add those
automatically, so if you put virtio devices in a config for a qemu
that has PCIe-capable virtio devices, you'll need to add extra
pcie-root-ports yourself. That requirement will be eliminated in a
future patch, but for now, it's simple to do this:
<controller type='pci' model='pcie-root-port'/>
<controller type='pci' model='pcie-root-port'/>
<controller type='pci' model='pcie-root-port'/>
...
Partially Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1330024
As with other devices assign the slot number right away when adding the
device. This will make the slot numbers static as we do with other
addressing elements and it will ultimately simplify allocation of the
alias in a static way which does not break with qemu.
We're keeping some things at default and that's not something we want to
do intentionally. Let's save some sensible defaults upfront in order to
avoid having problems later. The details for the defaults (of the newer
implementation) can be found in qemu's commit 5400c02b90bb:
http://git.qemu.org/?p=qemu.git;a=commit;h=5400c02b90bb
Since we are merely saving the defaults it will not change the guest ABI
and thanks to the fact that we're doing it in the PostParse callback it
will not break the ABI stability checks.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
The old ivshmem is deprecated in QEMU, so let's use the better
ivshmem-{plain,doorbell} variants instead.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Add an optional "tls='yes|no'" attribute for a TCP chardev.
For QEMU, this will allow for disabling the host config setting of the
'chardev_tls' for a domain chardev channel by setting the value to "no" or
to attempt to use a host TLS environment when setting the value to "yes"
when the host config 'chardev_tls' setting is disabled, but a TLS environment
is configured via either the host config 'chardev_tls_x509_cert_dir' or
'default_tls_x509_cert_dir'
Signed-off-by: John Ferlan <jferlan@redhat.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
The code is entirely correct, but it still managed to trip me
up when I first ran into it because I did not realize right away
that VIR_PCI_CONNECT_TYPES_ENDPOINT was not a single flag, but
rather a mask including both VIR_PCI_CONNECT_TYPE_PCI_DEVICE and
VIR_PCI_CONNECT_TYPE_PCIE_DEVICE.
In order to save the next distracted traveler in PCI Address Land
some time, document this fact with a comment. Add a test case for
the behavior as well.
It was missing... Also since I'm using the soft link from qemuxml2xmloutdata
to the qemuxml2argvdata file, modify the output file to have the necessary
<address> elements plus the mouse and keyboard.
Signed-off-by: John Ferlan <jferlan@redhat.com>
The x86 CPU driver translated each CPU definition from domain XML into
CPUID data and then back to CPU definition. This effectively sorted the
list of CPU features according to their CPUID values. Since this is
going to change, we need to reorder CPU features in a few test files to
make sure the generated QEMU command lines will not change.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Most of QEMU's PCI display device models, such as:
libvirt video/model/@type QEMU -device
------------------------- ------------
cirrus cirrus-vga
vga VGA
qxl qxl-vga
virtio virtio-vga
come with a linear framebuffer (sometimes called "VGA compatibility
framebuffer"). This linear framebuffer lives in one of the PCI device's
MMIO BARs, and allows guest code (primarily: firmware drivers, and
non-accelerated OS drivers) to display graphics with direct memory access.
Due to architectural reasons on aarch64/KVM hosts, this kind of
framebuffer doesn't / can't work in
qemu-system-(arm|aarch64) -M virt
machines. Cache coherency issues guarantee a corrupted / unusable display.
The problem has been researched by several people, including kvm-arm
maintainers, and it's been decided that the best way (practically the only
way) to have boot time graphics for such guests is to consolidate on
QEMU's "virtio-gpu-pci" device.
>From <https://bugzilla.redhat.com/show_bug.cgi?id=1195176>, libvirt
supports
<devices>
<video>
<model type='virtio'/>
</video>
</devices>
but libvirt unconditionally maps @type='virtio' to QEMU's "virtio-vga"
device model. (See the qemuBuildDeviceVideoStr() function and the
"qemuDeviceVideo" enum impl.)
According to the above, this is not right for the "virt" machine type; the
qemu-system-(arm|aarch64) binaries don't even recognize the "virtio-vga"
device model (justifiedly). Whereas "virtio-gpu-pci", which is a pure
virtio device without a compatibility framebuffer, is available, and works
fine.
(The ArmVirtQemu ("AAVMF") platform of edk2 -- that is, the UEFI firmware
for "virt" -- supports "virtio-gpu-pci", as of upstream commit
3ef3209d3028. See
<https://tianocore.acgmultimedia.com/show_bug.cgi?id=66>.)
Override the default mapping of "virtio", from "virtio-vga" to
"virtio-gpu-pci", if qemuDomainMachineIsVirt() evaluates to true.
Cc: Andrea Bolognani <abologna@redhat.com>
Cc: Drew Jones <drjones@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Martin Kletzander <mkletzan@redhat.com>
Suggested-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1372901
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Martin Kletzander <mkletzan@redhat.com>
Add a new TLS X.509 certificate type - "chardev". This will handle the
creation of a TLS certificate capability (and possibly repository) for
properly configured character device TCP backends.
Unlike the vnc and spice there is no "listen" or "passwd" associated. The
credentials eventually will be handled via a libvirt secret provided to
a specific backend.
Make use of the default verify option as well.
Signed-off-by: John Ferlan <jferlan@redhat.com>
When the user doesn't specify any model for a USB controller,
we use an architecture-dependent default, but we don't reflect
it in the guest XML.
Pick the default USB controller model when parsing the guest
XML instead of when creating the QEMU command line, so that
our choice is saved back to disk.
https://bugzilla.redhat.com/show_bug.cgi?id=1356937
Add the definitions to allow for viewing/setting cgroup period and quota
limits for IOThreads.
This is similar to the work done for emulator quota and period by
commit ids 'b65dafa' and 'e051c482'.
Being able to view/set the IOThread specific values is related to more
recent changes adding global period (commmit id '4d92d58f') and global
quota (commit id '55ecdae') definitions and qemu support (commit id
'4e17ff79' and 'fbcbd1b2'). With a global setting though, if somehow
the IOThread value in the cgroup hierarchy was set "outside of libvirt"
to a value that is incompatible with the global value.
Allowing control over IOThread specific values provides the capability
to alter the IOThread values as necessary.
To allow using failover with gluster it's necessary to specify multiple
volume hosts. Add support for starting qemu with such configurations.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
