[libvirt] [PATCH] cpuCompare: Fix comparison of two host CPUs

Jiri Denemark jdenemar at redhat.com
Tue Jul 13 10:03:43 UTC 2010

Hi Dan,

> I do not compare CPUs for fun, but rather to know if a guest can be run
> on a specific host. However, this is not exactly what
> virConnectCompareCPU gives me: A vmx-enabled host cpu is a superset of
> itself, but it would not run itself as a guest since we do not have
> nested vxm yet. Similarly, if we ever have svm-emulation-by-kvm, we
> could be running svm guests on a vmx host.
> Is it only me? Or should libvirt expose the more interesting meaning?

Absolutely, that would be just perfect. However, I believe libvirt does the
best it can. Only hypervisor itself knows that it can emulate some features
which are not present in host CPU or that some features cannot work in guests
even though host CPU provides them. For such advanced comparison, qemu would
need to provide a way for libvirt to ask for this stuff.


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