linux-kernel - Re: [RFC PATCH 06/12] perf: Support extension of sample

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Message-ID: <99087e26-192f-4fa6-b43b-0c6a39c45b38@linux.intel.com>
Date: Wed, 18 Jun 2025 09:52:12 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Mark Rutland <mark.rutland@....com>,
 "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>, 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, ak@...ux.intel.com, zide.chen@...el.com,
 broonie@...nel.org
Subject: Re: [RFC PATCH 06/12] perf: Support extension of sample_regs



On 2025-06-18 9:30 a.m., Peter Zijlstra wrote:
> On Wed, Jun 18, 2025 at 06:10:20AM -0400, Liang, Kan wrote:
> 
>> Maybe we should use a mask to replace the nr_vectors.
>> Because Dave mentioned that the XSAVES may fail.
> 
> XSAVE is a pain in the arse :/
> 
>> PERF_SAMPLE_SIMD_REGS := {
>> 	u64 vectors_mask;
>> 	u16 vector_length;
>> 	u64 pred_mask;
>> 	u16 pred_length;
> 
> That is not u64 aligned...

I didn't know we have the alignment requirement for the output.
If so,

PERF_SAMPLE_SIMD_REGS := {
	u64 vectors_mask;
	u64 pred_mask;
	u64 vector_length:16,
	    pred_length:16,
	    reserved:32;
	u64 data[];
}

Thanks,
Kan>
>> 	u64 data[];
>> }