linux-kernel - Re: [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query perfmon_event

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Date:   Wed, 9 Feb 2022 14:21:34 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Like Xu <like.xu.linux@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Like Xu <likexu@...cent.com>,
        Stephane Eranian <eranian@...gle.com>,
        David Dunn <daviddunn@...gle.com>
Subject: Re: [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query
 perfmon_event_map[] directly

On Wed, Feb 02, 2022 at 02:35:45PM -0800, Jim Mattson wrote:
> 3) TDX is going to pull the rug out from under us anyway. When the TDX
> module usurps control of the PMU, any active host counters are going
> to stop counting. We are going to need a way of telling the host perf
> subsystem what's happening, or other host perf clients are going to
> get bogus data.

That's not acceptible behaviour. I'm all for unilaterally killing any
guest that does this.