linux-kernel - Re: [Patch v4 07/13] perf/x86: Add constraint for guest perf metrics event

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Message-ID: <20231002122909.GC13957@noisy.programming.kicks-ass.net>
Date:   Mon, 2 Oct 2023 14:29:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ravi Bangoria <ravi.bangoria@....com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Dapeng Mi <dapeng1.mi@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Like Xu <likexu@...cent.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>, kvm@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhang Xiong <xiong.y.zhang@...el.com>,
        Lv Zhiyuan <zhiyuan.lv@...el.com>,
        Yang Weijiang <weijiang.yang@...el.com>,
        Dapeng Mi <dapeng1.mi@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        David Dunn <daviddunn@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Manali Shukla <manali.shukla@....com>
Subject: Re: [Patch v4 07/13] perf/x86: Add constraint for guest perf metrics
 event

On Fri, Sep 29, 2023 at 08:50:07PM +0530, Ravi Bangoria wrote:
> On 29-Sep-23 5:23 PM, Peter Zijlstra wrote:

> > I don't think you need to go that far, host can use PMU just fine as
> > long as it doesn't overlap with a vCPU. Basically, if you force
> > perf_attr::exclude_guest on everything your vCPU can haz the full thing.

^ this..

> How about keying off based on PMU specific KVM module parameter? Something
> like what Manali has proposed for AMD VIBS? Please see solution 1.1:
> 
> https://lore.kernel.org/r/3a6c693e-1ef4-6542-bc90-d4468773b97d@amd.com

So I hadn't read that, but isn't that more or less what I proposed
above?