Re: KVM PMU virtualization

Jes Sorensen
2010-02-26T13:37:12Z

On 02/26/10 14:18, Ingo Molnar wrote:
>
> * Avi Kivity<avi@redhat.com> wrote:
>
>> Can you emulate the Core 2 pmu on, say, a P4? [...]
>
> How about the Pentium? Or the i486?
>
> As long as there's perf events support, the CPU can be supported in a soft
> PMU. You can even cross-map exotic hw events if need to be - but most of the
> tooling (in just about any OS) uses just a handful of core events ...

This is only possible if all future CPU perfmon events are guaranteed
to be a superset of previous versions. Otherwise you end up emulating
events and providing randomly generated numbers back.

The perfmon revision and size we present to a guest has to match the
current host.

Jes