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Subject: Re: [PATCH v3 04/17] perf: x86/ds: Handle guest PEBS overflow PMI and
 inject it to guest
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Kan Liang <kan.liang@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>, eranian@google.com,
        kvm@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Andi Kleen <andi@firstfloor.org>, wei.w.wang@intel.com,
        luwei.kang@intel.com, linux-kernel@vger.kernel.org,
        Like Xu <like.xu@linux.intel.com>
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From:   "Xu, Like" <like.xu@intel.com>
Message-ID: <22b30bc7-84d2-b251-e558-1d8095c76187@intel.com>
Date:   Tue, 2 Feb 2021 14:31:16 +0800
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On 2021/1/25 19:47, Peter Zijlstra wrote:
> 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.

Thanks for this comment, and it's enlightening.

For the case that both host and guest PEBS are enabled,
the host PEBS PMI will be injected into the guest only when
GLOBAL_STATUS_BUFFER_OVF_BIT is not set in the guest global_status.

>