Re: Performance monitoring units and KVM

Balaji Rao
2008-01-30T19:14:10Z

On Wednesday 30 January 2008 11:56:25 pm Andi Kleen wrote:
> There is no really an architectural PMU if you consider
> boxes beyond relatively new Intel CPUs (which got one)
>
But since kvm runs only on such CPUs, it should not really be a problem in
migrating between various Intel models at least.
> But on the other hand in my experience most PMU users use
> relatively simple few counters (e.g. 90+% likely the local
> variant of CPU_CYCLES_NONHALTED) so it would be in theory
> possible to translate those by traps from a different CPU's
> format in the monitor into the local MSR.
>
> The only trouble is that is no architectural way to tell
> the guest "i support only counter X Y Z" and also no
> nice way to reject a particular counter except for just
> not ticking.
Can't this be exported through CPUID ?
>

regards,
balaji rao