[libvirt] Incompatible CPU after upgrading qemu

Hi All, I've been doing some upgrade testing and noticed a problem starting some existing VMs after upgrading qemu from 2.6 to 2.9 on one of my AMD machines. Using libvirt 3.2.0 and qemu 2.6, I have no problems starting a VM with the following machine/CPU config <os> <type arch='x86_64' machine='pc-i440fx-2.6'>hvm</type> <boot dev='hd'/> </os> <cpu mode='custom' match='exact'> <model fallback='allow'>Opteron_G4</model> </cpu> After upgrading qemu to 2.9 the VM fails to start with error: the CPU is incompatible with host CPU: Host CPU does not provide required features: svm I see that qemu commit 75d373ef disables SVM in KVM mode, but that change was made quite some time ago and pertains to all machine types > pc-i440fx-2.2. Perhaps the problem was revealed by Jiri's recent libvirt changes to detect host CPU model by asking qemu? My knee-jerk reaction is to remove 'svm' from Opteron CPUs in cpu_map.xml, but I'm far from the expert on the evolving CPU code in libvirt, so asking the experts here for some guidance. Regards, Jim