[Pkg-libvirt-maintainers] Bug#993856: SR-IOV vf assignment fails using network pool instead of hard-coded PCEe bus address

[Tim Small]

This bug still seems to be present in Trixie.  Looking at the contents of the
libvirt-<uuid>.files which is generated by libvirt, it's missing the necessary
PCI permissions when an SR-IOV virtual function is assigned via a network
instead of via a static PCI device address.

Specifically in this case, the following are missing from the permissions file:

"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/resource3" rw,
"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/vendor" rw,
"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/reset" rw,
"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/resource" rw,
"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/device" rw,
"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/resource0" rw,
"/sys/devices/pci0000:00/0000:00:1d.0/0000:03:10.1/config" rw,
"/dev/vfio/vfio" rw,
"/dev/vfio/[0-9]*" rw,

but the following is erroneously present:

"/dev/vhost-net" rw,


VM definition fragment which produces the behaviour:

    <interface type='network'>
      <mac address='52:54:00:e9:4b:bc'/>
      <source network='i350port1passthrough'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
    </interface>

Network definition:

<network>
  <name>i350port1passthrough</name>
  <uuid>389297b8-0f92-4523-9ad8-5d633cdddccf</uuid>
  <forward mode="hostdev" managed="yes">
    <pf dev="envftest"/>
  </forward>
</network>



Assigning via the pool is desirable because the PCIe devices are dynamically
assigned, so the bus slot assignments etc. are not guaranteed to persist.
Additionally live migration can fail unless the PCI device addresses are
identical on the source and destination hardware.

More details can be found in e.g. this article:

https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/virtualization_deployment_and_administration_guide/sect-pci_devices-pci_passthrough#sect-PCI_devices-PCI_passthrough