linux-kernel - Re: [Patch v5 08/19] perf/x86: Enable XMM sampling using sample_simd_vec_reg

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Message-ID: <f36e5477-d405-4da0-bdae-f79d496cf465@linux.intel.com>
Date: Mon, 8 Dec 2025 14:10:42 +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>,
 Thomas Gleixner <tglx@...utronix.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, Jiri Olsa <jolsa@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 Mark Rutland <mark.rutland@....com>, broonie@...nel.org,
 Ravi Bangoria <ravi.bangoria@....com>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, Zide Chen <zide.chen@...el.com>,
 Falcon Thomas <thomas.falcon@...el.com>, Dapeng Mi <dapeng1.mi@...el.com>,
 Xudong Hao <xudong.hao@...el.com>, Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [Patch v5 08/19] perf/x86: Enable XMM sampling using
 sample_simd_vec_reg_* fields


On 12/5/2025 7:25 PM, Peter Zijlstra wrote:
> On Wed, Dec 03, 2025 at 02:54:49PM +0800, Dapeng Mi wrote:
>
>> diff --git a/arch/x86/include/uapi/asm/perf_regs.h b/arch/x86/include/uapi/asm/perf_regs.h
>> index 7c9d2bb3833b..c3862e5fdd6d 100644
>> --- a/arch/x86/include/uapi/asm/perf_regs.h
>> +++ b/arch/x86/include/uapi/asm/perf_regs.h
>> @@ -55,4 +55,21 @@ enum perf_event_x86_regs {
>>  
>>  #define PERF_REG_EXTENDED_MASK	(~((1ULL << PERF_REG_X86_XMM0) - 1))
>>  
>> +enum {
>> +	PERF_REG_X86_XMM,
>> +	PERF_REG_X86_MAX_SIMD_REGS,
>> +};
>> +
>> +enum {
>> +	PERF_X86_SIMD_XMM_REGS      = 16,
>> +	PERF_X86_SIMD_VEC_REGS_MAX  = PERF_X86_SIMD_XMM_REGS,
>> +};
>> +
>> +#define PERF_X86_SIMD_VEC_MASK		GENMASK_ULL(PERF_X86_SIMD_VEC_REGS_MAX - 1, 0)
>> +
>> +enum {
>> +	PERF_X86_XMM_QWORDS      = 2,
>> +	PERF_X86_SIMD_QWORDS_MAX = PERF_X86_XMM_QWORDS,
>> +};
>> +
>>  #endif /* _ASM_X86_PERF_REGS_H */
> I don't understand this bit -- the next few patches add to it for YMM
> and ZMM, but what's the point? I don't see why this is needed at all,
> let alone why it needs to be UABI.

Currently these bits are only used in user space perf tools. Let me remove
it from the header perf_regs.h.


>