Cloning bug for 6.4.
This depends on bug 692374, that is about making "-cpu enforce" work reliably.
+++ This bug was initially created as a clone of Bug #822148 +++
Description of problem:
To make sure libvirt is always getting exactly the CPU flags it asked qemu for, it has to use "-cpu <model>,enforce", so qemu won't start if the requested flags can't be exposed.
This may be a problem in case users have existing VMs that are working perfectly for them, but would fail to start if "enforce" is used. Maybe the new behavior could be enabled only for new machine-types?