[libvirt-users] PCI passthrough fails in virsh: iommu group is not viable

Wed Aug 12 21:12:19 UTC 2015

On 08/12/2015 02:34 PM, Alex Holst wrote:
> I would really appreciate some pointers on what I am doing wrong here.
>
> I have a need to run multiple virtual guests which have each their own GPU and
> some USB controllers passed-through. I am able to run one of the guests like
> this (assuming vfio stuff has happened elsewhere), but I would prefer to use
> virsh:
>
> kvm -M q35 -m 8192 -cpu host,kvm=off \
>   -smp 4,sockets=1,cores=4,threads=1 \
>   -bios /usr/share/seabios/bios.bin -vga none \
>   -device ioh3420,bus=pcie.0,addr=1c.0,multifunction=on,port=1,chassis=1,id=root.1 \
>   -device vfio-pci,host=02:00.0,bus=root.1,addr=00.0,multifunction=on,x-vga=on \
>   -device vfio-pci,host=02:00.1,bus=root.1,addr=00.1 \
>   -device vfio-pci,host=00:1d.0,bus=pcie.0 \
>   -device vfio-pci,host=00:1a.0,bus=pcie.0 \
>   -nographic -boot menu=on /vm2/foo.img
>
> I found the hardware addresses using lspci.  When I invoke the same machine with virsh with what 
> I believe are the same addresses,

1) The XML that you provide at the end shows you only assigning 02:00.0,
but not 02:00.1, and you are using managed='yes', so you are depending
on libvirt to unbind any host driver and bind vfio-pci to the devices.
If 02:00.0 and 02:00.1 are both in iommu group 18, but one of them isn't
bound to vfio-pci, qemu will give "some kind of error" when it tries to
assign any other device in the group.

2) your example qemu commandline uses the q35 machinetype, but your
example libvirt domain uses pc-i440fx-utopic machinetype, so the bus
structure is completely different. Assuming a recent enough libvirt, you
should be able to create a virtual machine based on q35 and attach the
devices to pcie-root (bus 0). You wouldn't be able to add an ioh3420
controller in unless you are running libvirt built from upstream master
- support for that was just pushed last weekend. (it is a new controller
defined like this:

  <controller type='pci' model='pcie-root-port'/>

3) Doing the above *may* eliminate another problem that your current
definition has - it has an emulated video device at 00:02.0, then the
passthrough video device at 00:04.0. It's likely that even if you do get
the domain started up, you'll end up with the passthrough vga as a
secondary (which I'm guessing isn't what you want).

4) I don't know what "x-vga=on" is, but libvirt doesn't directly support
that. If it is necessary, you would need to add it using libvirt's "qemu
commandline passthrough":

http://blog.vmsplice.net/2011/04/how-to-pass-qemu-command-line-options.html

(you can add a "-set", "device.hostdev0.x-vga=on" I think)

5) The libvirt definition you've provided add several other devices that
you don't have in your qemu commandline which may get in the way of what
you want to do; in particular the tablet, mouse, and keyboard. You'll
probably want to trim those out (and if you're passing through USB,
you'll likely want to replace all of the <controller type='usb'>
elements with a single <controller type='usb' model='none'/>

6) your qemu commandline specifies an exact bios location, which you
haven't done in the libvirt definition. If that isn't the default bios,
then you'll want to look into how to specify a non-default bios file
here: http://www.libvirt.org/formatdomain.html

7) If you're going to stick with the pc-ii440fx machinetype and your
guest doesn't absolutely require a SATA disk, you'd probably be better
off letting it attach to the 440fx's IDE controller instead (or even
better, if your guest OS supports the virtio disk driver, use that since
the performance will be *greatly* improved). (likewise, replace the
network interface's "model type='e1000'" with "model type='virtio'" if
you can).

>  I get:
>
> virsh # start foo
> error: Failed to start domain foo
> error: internal error: process exited while connecting to monitor: 2015-08-12T18:24:10.651720Z qemu-system-x86_64: -device vfio-pci,host=02:00.0,id=hostdev0,bus=pci.0,addr=0x4: vfio: error, group 18 is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver.
> 2015-08-12T18:24:10.651752Z qemu-system-x86_64: -device vfio-pci,host=02:00.0,id=hostdev0,bus=pci.0,addr=0x4: vfio: failed to get group 18
> 2015-08-12T18:24:10.651766Z qemu-system-x86_64: -device vfio-pci,host=02:00.0,id=hostdev0,bus=pci.0,addr=0x4: Device initialization failed.
> 2015-08-12T18:24:10.651781Z qemu-system-x86_64: -device vfio-pci,host=02:00.0,id=hostdev0,bus=pci.0,addr=0x4: Device 'vfio-pci' could not be initialized
>
> I have included dumpxml output below -- is the hostdev section wrong?
>
> <domain type='kvm'>
>   <name>foo</name>
>   <uuid>51f57655-11be-41bf-b925-2e6aef01f9c4</uuid>
>   <memory unit='KiB'>8388608</memory>
>   <currentMemory unit='KiB'>8388608</currentMemory>
>   <vcpu placement='static' current='1'>4</vcpu>
>   <os>
>     <type arch='x86_64' machine='pc-i440fx-utopic'>hvm</type>
>     <bootmenu enable='yes'/>
>   </os>
>   <features>
>     <acpi/>
>     <apic/>
>     <pae/>
>     <hyperv>
>       <relaxed state='on'/>
>       <vapic state='on'/>
>       <spinlocks state='on' retries='8191'/>
>     </hyperv>
>   </features>
>   <cpu mode='custom' match='exact'>
>     <model fallback='allow'>SandyBridge</model>
>     <topology sockets='1' cores='4' threads='1'/>
>   </cpu>
>   <clock offset='localtime'>
>     <timer name='rtc' tickpolicy='catchup'/>
>     <timer name='pit' tickpolicy='delay'/>
>     <timer name='hpet' present='no'/>
>     <timer name='hypervclock' present='yes'/>
>   </clock>
>   <on_poweroff>destroy</on_poweroff>
>   <on_reboot>restart</on_reboot>
>   <on_crash>restart</on_crash>
>   <pm>
>     <suspend-to-mem enabled='no'/>
>     <suspend-to-disk enabled='no'/>
>   </pm>
>   <devices>
>     <emulator>/usr/bin/kvm-spice</emulator>
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='raw'/>
>       <source file='/vm2/foo.img'/>
>       <target dev='sda' bus='sata'/>
>       <boot order='1'/>
>       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>     </disk>
>     <disk type='block' device='cdrom'>
>       <driver name='qemu' type='raw'/>
>       <target dev='hdb' bus='ide'/>
>       <readonly/>
>       <boot order='2'/>
>       <address type='drive' controller='0' bus='0' target='0' unit='1'/>
>     </disk>
>     <controller type='usb' index='0' model='ich9-ehci1'>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x7'/>
>     </controller>
>     <controller type='usb' index='0' model='ich9-uhci1'>
>       <master startport='0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0' multifunction='on'/>
>     </controller>
>     <controller type='usb' index='0' model='ich9-uhci2'>
>       <master startport='2'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x1'/>
>     </controller>
>     <controller type='usb' index='0' model='ich9-uhci3'>
>       <master startport='4'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x2'/>
>     </controller>
>     <controller type='pci' index='0' model='pci-root'/>
>     <controller type='ide' index='0'>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
>     </controller>
>     <controller type='virtio-serial' index='0'>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
>     </controller>
>     <controller type='sata' index='0'>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
>     </controller>
>     <interface type='direct'>
>       <mac address='52:54:00:f0:47:f5'/>
>       <source dev='p5p1' mode='bridge'/>
>       <model type='e1000'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
>     </interface>
>     <serial type='pty'>
>       <target port='0'/>
>     </serial>
>     <console type='pty'>
>       <target type='serial' port='0'/>
>     </console>
>     <channel type='spicevmc'>
>       <target type='virtio' name='com.redhat.spice.0'/>
>       <address type='virtio-serial' controller='0' bus='0' port='1'/>
>     </channel>
>     <input type='tablet' bus='usb'/>
>     <input type='mouse' bus='ps2'/>
>     <input type='keyboard' bus='ps2'/>
>     <graphics type='spice' autoport='yes'/>
>     <video>
>       <model type='cirrus' vram='16384' heads='1'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
>     </video>
>     <hostdev mode='subsystem' type='pci' managed='yes'>
>       <source>
>         <address domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
>       </source>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
>     </hostdev>
>     <memballoon model='virtio'>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
>     </memballoon>
>   </devices>
> </domain>
>