linux-kernel - Re: [PATCH v3 04/17] perf: x86/ds: Handle guest PEBS overflow PMI and inject it to guest

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Date:   Mon, 25 Jan 2021 12:47:23 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Like Xu <like.xu@...ux.intel.com>
Cc:     Kan Liang <kan.liang@...ux.intel.com>,
        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>, wei.w.wang@...el.com,
        luwei.kang@...el.com, linux-kernel@...r.kernel.org,
        "Xu, Like" <like.xu@...el.com>
Subject: Re: [PATCH v3 04/17] perf: x86/ds: Handle guest PEBS overflow PMI
 and inject it to guest

On Mon, Jan 25, 2021 at 04:26:22PM +0800, Like Xu wrote:

> In the host and guest PEBS both enabled case,
> we'll get a crazy dmesg *bombing* about spurious PMI warning
> if we pass the host PEBS PMI "harmlessly" to the guest:
> 
> [11261.502536] Uhhuh. NMI received for unknown reason 2c on CPU 36.
> [11261.502539] Do you have a strange power saving mode enabled?
> [11261.502541] Dazed and confused, but trying to continue

How? AFAICT handle_pmi_common() will increment handled when
GLOBAL_STATUS_BUFFER_OVF_BIT is set, irrespective of DS containing
data.