linux-kernel - Re: [Patch v2 15/24] perf/x86/intel: Add SSP register support for arch-PEBS

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Message-ID: <20250225115229.GN11590@noisy.programming.kicks-ass.net>
Date: Tue, 25 Feb 2025 12:52:29 +0100
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 v2 15/24] perf/x86/intel: Add SSP register support for
 arch-PEBS

On Tue, Feb 18, 2025 at 03:28:09PM +0000, Dapeng Mi wrote:

> +	if (unlikely(event->attr.sample_regs_intr & BIT_ULL(PERF_REG_X86_SSP))) {
> +		/* Only arch-PEBS supports to capture SSP register. */
> +		if (!x86_pmu.arch_pebs || !event->attr.precise_ip)
> +			return -EINVAL;
> +	}

> @@ -27,9 +27,11 @@ enum perf_event_x86_regs {
>  	PERF_REG_X86_R13,
>  	PERF_REG_X86_R14,
>  	PERF_REG_X86_R15,
> +	/* Shadow stack pointer (SSP) present on Clearwater Forest and newer models. */
> +	PERF_REG_X86_SSP,

The first comment makes more sense. Nobody knows of cares what a
clearwater forest is, but ARCH-PEBS is something you can check.

Also, this hard implies that anything exposing ARCH-PEBS exposes
CET-SS. Does virt complicate this?