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Lech's questions

Martin Hope
Lech
Asked: 2024-12-18 22:41:03 +0800 CST
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I'm trying to run a KVM/QEMU VM under RHEL9 that uses a virtualized Infiniband card (VF) through SR-IOV from a pool of VFs. I can specify a certain VF's PCI device with hostdev and that works just fine, however that requires hardcoding the PCI bus/slot/etc. into the VM XML sheet. That'd be a problem when migrating the VM to another server. So I'd rather define a network pool of VFs as described in this RH doc that would assign a free VF to a newly started VM automatically.

I did everything as described in the docs and the network pool of 8 VFs from a single IB card works like it should:

# virsh net-dumpxml IB-passthrough
<network>
  <name>IB-passthrough</name>
  <uuid>8dce28fa-97ea-43d4-a82b-5923fa1a2a4f</uuid>
  <forward mode='hostdev' managed='yes'>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x1'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x2'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x3'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x4'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x5'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x6'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x00' function='0x7'/>
    <address type='pci' domain='0x0000' bus='0xc1' slot='0x01' function='0x0'/>
  </forward>
</network>

I write the following entry into the VM's XML:

<interface type='network'>
  <source network='IB-passthrough'/>
</interface>

But after closing the XML editor, the entry gets automatically extended with mac and address entries:

<interface type='network'>
  <mac address='52:54:00:44:db:0d'/>
  <source network='IB-passthrough'/>
  <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
</interface>

Then the VM cannot be started since the MAC cannot be set:

# virsh start rhel9.2-testvm
    error: Failed to start domain 'rhel9.2-testvm'
    error: Cannot set interface MAC to 52:54:00:05:72:5c for ifname ibp193s0 vf 0: Operation not supported

Is there a way to omit that automatic MAC? Or the Interface MAC change? Or is there another problem that I'm missing?

kvm-virtualization