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

[Alex Holst]

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, 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>

-- 
Alex Holst