linux-kernel - Re: [RFC] [PATCH v2 0/5] Intel Virtual PMU Optimization

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Message-ID: <20190325155827.GI18020@tassilo.jf.intel.com>
Date:   Mon, 25 Mar 2019 08:58:27 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Like Xu <like.xu@...ux.intel.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, like.xu@...el.com, wei.w.wang@...el.com,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] [PATCH v2 0/5] Intel Virtual PMU Optimization

> It isn't going anywhere anyway, its insane. You let perf do all its
> normal things and then discard the results by avoiding the wrmsr.
> 
> Then you fudge a second wrmsr path somewhere.
> 
> Please, just make the existing event dtrt.

I still think the right way is to force an event to a counter
from an internal field. And then set that field from KVM.
This is quite straight forward to do in the event scheduler.

I did it for some experimential PEBS virtualization patches
which require the same because they have to expose the
counter indexes inside the PEBS record to the guest.

-Andi