[Bug 1417623] [NEW] Libvirt forbids assigning passthrough device to pci-express root on q35

[Vladimir Sherstnikov]

Public bug reported:

Release: any
Version: 1.2.8

Expected: Assigning host device to pcie-root like this:

<domain type='kvm'>
...
  <os>
    <type arch='x86_64' machine='pc-q35-2.0'>hvm</type>
  </os>
...
    <controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='dmi-to-pci-bridge'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1e' function='0x0'/>
    </controller>
    <controller type='pci' index='2' model='pci-bridge'>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x01' function='0x0'/>
    </controller>
...
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <source>
        <address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
      </source>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </hostdev>
...
</domain>

Happened instead: When trying to save, a message comes:
error: XML error: PCI bus is not compatible with the device at 0000:01:00.0. Device requires a standard PCI slot, which is not provided by bus 0000:00
Failed. Try again? [y,n,f,?]:

However  such assignment works well, when I use qemu commandline.
Moreover, standart video card (std/currus) comes exactly to  pcie-root.
So, this restriction doesn't make any sense. I think, we should have
ability to choose, what bus to use for passed-through devices.

** Affects: libvirt (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1417623

Title:
  Libvirt forbids assigning passthrough device to pci-express root on
  q35

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