Re: KVM PMU virtualization

Avi Kivity
2010-03-08T10:15:58Z

On 03/01/2010 07:17 PM, Peter Zijlstra wrote:
>
>
>> 2. For every emulated performance counter the guest activates kvm
>> allocates a perf_event and configures it for the guest (we may allow
>> kvm to specify the counter index, the guest would be able to use
>> rdpmc unintercepted then). Event filtering is also done in this step.
>>
> rdpmc can never be used unintercepted, for perf might be multiplexing
> the actual hw.
>

How often is rdpmc used? If it is invoked on high frequency
software-only events (like context switches), then this may be a
performance issue. If it is only issued on perf interrupts, we may be
able to live with it (since we already took an exit for the interrupt).

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