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

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Message-ID: <20250415134829.GB4031@noisy.programming.kicks-ass.net>
Date: Tue, 15 Apr 2025 15:48:29 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Dapeng Mi <dapeng1.mi@...ux.intel.com>
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 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 :-)