pci-stub error and MSI-X for KVM guest

Fischer, Anna
2009-12-21T18:16:39Z

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.

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.

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.

Thanks,
Anna