linux-kernel - Re: [kvm-unit-tests Patch 4/5] x86: pmu: Support validation for Intel PMU fixed counter 3

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Date:   Wed, 25 Oct 2023 05:38:25 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhang Xiong <xiong.y.zhang@...el.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Like Xu <like.xu.linux@...il.com>,
        Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [kvm-unit-tests Patch 4/5] x86: pmu: Support validation for Intel
 PMU fixed counter 3

On Wed, Oct 25, 2023 at 4:26 AM Mi, Dapeng <dapeng1.mi@...ux.intel.com> wrote:
>
>
> On 10/25/2023 3:05 AM, Jim Mattson wrote:
> > On Tue, Oct 24, 2023 at 12:51 AM Dapeng Mi <dapeng1.mi@...ux.intel.com> wrote:
> >> Intel CPUs, like Sapphire Rapids, introduces a new fixed counter
> >> (fixed counter 3) to counter/sample topdown.slots event, but current
> >> code still doesn't cover this new fixed counter.
> >>
> >> So add code to validate this new fixed counter.
> > Can you explain how this "validates" anything?
>
>
> I may not describe the sentence clearly. This would validate the fixed
> counter 3 can count the slots event and get a valid count in a
> reasonable range. Thanks.

I thought the current vPMU implementation did not actually support
top-down slots. If it doesn't work, how can it be validated?

>
> >
> >> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
> >> ---
> >>   x86/pmu.c | 3 ++-
> >>   1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/x86/pmu.c b/x86/pmu.c
> >> index 1bebf493d4a4..41165e168d8e 100644
> >> --- a/x86/pmu.c
> >> +++ b/x86/pmu.c
> >> @@ -46,7 +46,8 @@ struct pmu_event {
> >>   }, fixed_events[] = {
> >>          {"fixed 1", MSR_CORE_PERF_FIXED_CTR0, 10*N, 10.2*N},
> >>          {"fixed 2", MSR_CORE_PERF_FIXED_CTR0 + 1, 1*N, 30*N},
> >> -       {"fixed 3", MSR_CORE_PERF_FIXED_CTR0 + 2, 0.1*N, 30*N}
> >> +       {"fixed 3", MSR_CORE_PERF_FIXED_CTR0 + 2, 0.1*N, 30*N},
> >> +       {"fixed 4", MSR_CORE_PERF_FIXED_CTR0 + 3, 1*N, 100*N}
> >>   };
> >>
> >>   char *buf;
> >> --
> >> 2.34.1
> >>