Hi, I've been using libvirt (versions 0.9.11.5, and recently upgraded to 0.10.2), and have been attaching an SR-IOV VF to my VM with the following device configuration: <hostdev mode='subsystem' type='pci' managed='yes'> <source> <address domain='0x0000' bus='0x07' slot='0x10' function='0x0'/> </source> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> </hostdev> I had no problems with bringing up the VM and using the VF with this configuration. Recently I noticed that I would be able to assign a mac address to the SR-IOV VF if I used the interface configuration and changed over to using: <interface type='hostdev'> <mac address='52:54:00:d3:23:4f'/> <source> <address type='pci' domain='0x0000' bus='0x07' slot='0x10' function='0x0'/> </source> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> My VM fails to start up with this interface configuration. The error reported is: error: Failed to start domain exp85-1 error: An error occurred, but the cause is unknown When I look into /var/log/messages I see the following messages: Oct 15 15:25:48 dcswitch85 libvirtd[17709]: 2012-10-15 22:25:48.145+0000: 17713: error : virFileReadAll:457 : Failed to open file '/var/run/libvirt/qemu/p1p1_vf0': No such file or directory Oct 15 15:25:48 dcswitch85 libvirtd[17709]: 2012-10-15 22:25:48.146+0000: 17713: error : qemuRemoveCgroup:740 : internal error Unable to find cgroup for exp85-1 Oct 15 15:25:48 dcswitch85 libvirtd[17709]: 2012-10-15 22:25:48.146+0000: 17713: warning : qemuProcessStop:4136 : Failed to remove cgroup for exp85-1 I was wondering if anyone else has faced this problem or has a solution to this. I'm using Fedora17, KVM, and an 82599EB Intel NIC. Thanks much in advance. With best regards Radhika