[libvirt] Missing CPU vendor in capabilities in 1.2.18+

Hi, We have a report in Debian[1] where after a update from 1.2.16 to 1.2.18 VMs on a Intel i5 CPU fail to start due to libvirt not being able to match the CPU vendor: # virsh start sid error: Failed to start domain sid error: unsupported configuration: guest and host CPU are not compatible: host CPU vendor does not match required CPU vendor Intel The root cause seems to be that the <vendor> element is missing from the hosts capabilities. While I have: $ virsh capabilities | xpath -q -e //host/cpu/vendor <vendor>Intel</vendor> on my Intel box the reporters machine with a Core i5 the <vendor> element is just empty. Any idea what could have triggered this? This is still broken in 1.2.19-rc1. The bug has more details and logs attached. Any pointers would be welcome since I don't have access to such a machine atm to step through src/cpu/cpu_x86.c. Cheers, -- Guido [1] http://bugs.debian.org/797513