linux-kernel - Re: [RFC PATCH 01/41] perf: x86/intel: Support PERF_PMU_CAP_VPMU

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Message-ID: <56a98cae-36c5-40f8-8554-77f9d9c9a1b0@linux.intel.com>
Date: Thu, 11 Apr 2024 13:21:20 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Xiong Zhang <xiong.y.zhang@...ux.intel.com>
Cc: pbonzini@...hat.com, peterz@...radead.org, mizhang@...gle.com,
 kan.liang@...el.com, zhenyuw@...ux.intel.com, dapeng1.mi@...ux.intel.com,
 jmattson@...gle.com, kvm@...r.kernel.org, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org, zhiyuan.lv@...el.com, eranian@...gle.com,
 irogers@...gle.com, samantha.alt@...el.com, like.xu.linux@...il.com,
 chao.gao@...el.com
Subject: Re: [RFC PATCH 01/41] perf: x86/intel: Support
 PERF_PMU_CAP_VPMU_PASSTHROUGH



On 2024-04-11 1:04 p.m., Sean Christopherson wrote:
> On Fri, Jan 26, 2024, Xiong Zhang wrote:
>> From: Kan Liang <kan.liang@...ux.intel.com>
>>
>> Define and apply the PERF_PMU_CAP_VPMU_PASSTHROUGH flag for the version 4
>> and later PMUs
> 
> Why?  I get that is an RFC, but it's not at all obvious to me why this needs to
> take a dependency on v4+.

The IA32_PERF_GLOBAL_STATUS_RESET/SET MSRs are introduced in v4. They
are used in the save/restore of PMU state. Please see PATCH 23/41.
So it's limited to v4+ for now.

Thanks,
Kan