linux-kernel - Re: [PATCH v3 05/17] KVM: x86/pmu: Reprogram guest PEBS event to emulate guest PEBS counter

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Date:   Fri, 15 Jan 2021 12:33:46 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Like Xu <like.xu@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, eranian@...gle.com,
        kvm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <andi@...stfloor.org>,
        Kan Liang <kan.liang@...ux.intel.com>, wei.w.wang@...el.com,
        luwei.kang@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/17] KVM: x86/pmu: Reprogram guest PEBS event to
 emulate guest PEBS counter

On Mon, Jan 04, 2021 at 09:15:30PM +0800, Like Xu wrote:
> When a guest counter is configured as a PEBS counter through
> IA32_PEBS_ENABLE, a guest PEBS event will be reprogrammed by
> configuring a non-zero precision level in the perf_event_attr.
> 
> The guest PEBS overflow PMI bit would be set in the guest
> GLOBAL_STATUS MSR when PEBS facility generates a PEBS
> overflow PMI based on guest IA32_DS_AREA MSR.
> 
> The attr.precise_ip would be adjusted to a special precision
> level when the new PEBS-PDIR feature is supported later which
> would affect the host counters scheduling.

This seems like a random collection of changes, all required, but
loosely related.

> The guest PEBS event would not be reused for non-PEBS
> guest event even with the same guest counter index.

/me rolls eyes at the whole destroy+create nonsense...