linux-kernel - Re: [Patch v5 16/19] perf/x86: Activate back-to-back NMI detection for arch-PEBS induced NMIs

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Message-ID: <591264e1-0371-48ee-8509-554a05836189@linux.intel.com>
Date: Mon, 8 Dec 2025 16:53:47 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo
 <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, Jiri Olsa <jolsa@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 Mark Rutland <mark.rutland@....com>, broonie@...nel.org,
 Ravi Bangoria <ravi.bangoria@....com>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, Zide Chen <zide.chen@...el.com>,
 Falcon Thomas <thomas.falcon@...el.com>, Dapeng Mi <dapeng1.mi@...el.com>,
 Xudong Hao <xudong.hao@...el.com>
Subject: Re: [Patch v5 16/19] perf/x86: Activate back-to-back NMI detection
 for arch-PEBS induced NMIs


On 12/8/2025 4:50 PM, Peter Zijlstra wrote:
> On Mon, Dec 08, 2025 at 02:46:44PM +0800, Mi, Dapeng wrote:
>
>> This change only take effects for arch-PEBS. For the legacy PEBS, the
>> "handled" would still be added 1 unconditionally even the *_drain_pebs()
>> helpers always return 0.
>>
>>     /*
>>      * PEBS overflow sets bit 62 in the global status register
>>      */
>>     if (__test_and_clear_bit(GLOBAL_STATUS_BUFFER_OVF_BIT, (unsigned long
>> *)&status)) {
>>         u64 pebs_enabled = cpuc->pebs_enabled;
>>
>>         handled++;
>>         x86_pmu_handle_guest_pebs(regs, &data);
>>         static_call(x86_pmu_drain_pebs)(regs, &data);
>>
> Oh gawd. Please don't do that. If you change the calling convention of
> that function, please have it be used consistently.

Sure. I would do same change for legacy PEBS and make the behavior consistent. 


>