Re: pci-stub error and MSI-X for KVM guest

Chris Wright
2009-12-21T19:19:30Z

* Fischer, Anna (anna.fischer@hp.com) wrote:
> I am running Fedora Core 12 with a 2.6.31 kernel. I use the Intel
> 82576 SR-IOV network card and want to assign its Virtual Functions (VFs)
> to separate KVM guests. My guests also run Fedora Core 12 with a 2.6.31
> kernel. I use the latest igb driver in the host OS and load it with 2
> VFs activated. Then I assign those to my KVM guests. I use virt-manager
> to do this which then takes care of configuring pci-stub.

By 2.6.31 are you referring to the stock Fedora 12 kernel package?

> This works fine in principle and I can see the PCI device in the
> guest under lspci. However, the 82576 VF driver requires the OS
> to support MSI-X. My Fedora installation is configured with MSI-X,
> e.g. CONFIG_PCI_MSI is 'y'. When I load the driver it tells me it cannot
> initialize MSI-X for the device, and under /proc/interrupts I can see
> that MSI-X does not seem to work. Is this a KVM/QEMU limitation? It works
> for me when running the VF driver under a non-virtualized Linux system.

No, this should work fine. QEMU/KVM supports MSI-X to guest as well as
VFs.

> Also, when I do an lspci on the KVM guest, that is fine, but when I
> do an lspci -v then the guest crashes down. In the host OS under dmesg
> I can see this:
>
> pci-stub 0000:03:10.0: restoring config space at offset 0x1 (was 0x100000, writing 0x100004)
>
> Is this a known issue? My qemu-kvm version is 2:0.11.0.

No, I've not seen the crash before. What do you mean "the guest crashes
down"?

This looks like a Fedora specific version (rpm version). Can you verify
this is from Fedora packages vs. upstream source? If it's Fedora,
would be useful to open a bug there.

thanks,
-chris