Re: [PATCH] KVM: x86: Adjust counter sample period after a wrmsr

[Like Xu]

On 2020/2/25 8:08, Eric Hankland wrote:
> Hi Like -
>
> Thanks for the feedback - is your recommendation to do the read and
> period change at the same time and only take the lock once or is there
> another way around this while still handling writes correctly?

For non-running counters(the most common situation), we have too many
chances to reflect their new periods. In this case, calling
perf_event_period() in the trap of counter msr is redundant and burdensome.

A better way is to check if this counter is running via
pmc_speculative_in_use (), and if so,
just trigger kvm_make_request(KVM_REQ_PMU, pmc->vcpu).

Thanks,
Like Xu

> Eric