linux-kernel - Re: [RFC PATCH 00/12] Support vector and more extended registers in perf

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Message-ID: <20250617173420.GA1613376@noisy.programming.kicks-ass.net>
Date: Tue, 17 Jun 2025 19:34:20 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Liang, Kan" <kan.liang@...ux.intel.com>
Cc: mingo@...hat.com, acme@...nel.org, namhyung@...nel.org,
	tglx@...utronix.de, dave.hansen@...ux.intel.com, irogers@...gle.com,
	adrian.hunter@...el.com, jolsa@...nel.org,
	alexander.shishkin@...ux.intel.com, linux-kernel@...r.kernel.org,
	dapeng1.mi@...ux.intel.com, ak@...ux.intel.com, zide.chen@...el.com
Subject: Re: [RFC PATCH 00/12] Support vector and more extended registers in
 perf

On Tue, Jun 17, 2025 at 11:23:10AM -0400, Liang, Kan wrote:
> 
> 
> On 2025-06-17 10:29 a.m., Peter Zijlstra wrote:
> > On Tue, Jun 17, 2025 at 09:52:12AM -0400, Liang, Kan wrote:
> > 
> >> OK. So the sample_simd_reg_words actually has another meaning now.
> > 
> > Well, any simd field being non-zero means userspace knows about it. Sort
> > of an implicit flag.
> 
> Yes, but the tool probably wouldn't to touch any simd fields if user
> doesn't ask for simd registers

Trivial enough to have the tool unconditionally write a simd_words size
if the attr thing is big enough. But sure, whatever :-)