linux-kernel - Re: [Patch v3 11/22] perf/x86/intel: Allocate arch-PEBS buffer and initialize PEBS

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Message-ID: <5a9f25a8-7679-4619-8fa1-97ab86dc6104@linux.intel.com>
Date: Wed, 16 Apr 2025 09:03:30 +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>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Kan Liang <kan.liang@...ux.intel.com>, Andi Kleen <ak@...ux.intel.com>,
 Eranian Stephane <eranian@...gle.com>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [Patch v3 11/22] perf/x86/intel: Allocate arch-PEBS buffer and
 initialize PEBS_BASE MSR


On 4/15/2025 9:48 PM, Peter Zijlstra wrote:
> On Tue, Apr 15, 2025 at 11:44:17AM +0000, Dapeng Mi wrote:
>
>> +void fini_arch_pebs_buf_on_cpu(int cpu)
>> +{
>> +	if (!x86_pmu.arch_pebs)
>> +		return;
>> +
>> +	release_pebs_buffer(cpu);
>> +	wrmsr_on_cpu(cpu, MSR_IA32_PEBS_BASE, 0, 0);
>> +}
> So first we free the pages, and then we tell the hardware to not write
> into them again.
>
> What could possibly go wrong :-)

Oh, yes. Thanks for pointing this. I would exchange the sequence.