Re: [Patch v9 05/10] perf regs: Support x86 eGPRs/SSP sampling

["Mi, Dapeng" <dapeng1.mi@linux.intel.com>]

On 7/6/2026 10:59 AM, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] Reclaiming XMM register space breaks explicit XMM register selection on SIMD-capable hosts.
> --
>
> commit 4a688e42468a5e89b85174c21cc87866b350369c
> Author: Dapeng Mi <dapeng1.mi@linux.intel.com>
>
> perf regs: Support x86 eGPRs/SSP sampling
>
> This commit adds support for sampling x86 extended GP registers (R16-R31)
> and the shadow stack pointer (SSP) by reclaiming the original XMM register
> space. A new abi argument is introduced to distinguish the register layout,
> defaulting to the new SIMD layout on supported platforms.
>
>> diff --git a/tools/perf/util/parse-regs-options.c b/tools/perf/util/parse-regs-options.c
>> --- a/tools/perf/util/parse-regs-options.c
>> +++ b/tools/perf/util/parse-regs-options.c
> [ ... ]
>> @@ -87,14 +100,16 @@ __parse_regs(const struct option *opt, const char *str, int unset, bool intr)
>>  			*p = '\0';
>>  
>>  		if (!strcmp(s, "?")) {
>> -			list_perf_regs(stderr, mask);
>> +			list_perf_regs(stderr, mask, abi);
>>  			goto error;
>>  		}
>>  
>> -		reg_mask = name_to_perf_reg_mask(s, mask);
>> -		if (reg_mask == 0) {
>> -			ui__warning("Unknown register \"%s\", check man page or run \"perf record %s?\"\n",
>> -				s, intr ? "-I" : "--user-regs=");
>> +		reg_mask = name_to_perf_reg_mask(s, mask, abi);
>> +		if (reg_mask) {
>> +			if (abi & PERF_SAMPLE_REGS_ABI_SIMD)
>> +				opts->sample_simd_regs_enabled = 1;
>> +		} else {
>> +			ui__warning(warn, s, intr ? "-I" : "--user-regs=");
> [Severity: Medium]
> Will this change break explicit XMM register selection on SIMD-capable hosts?
>
> Because PERF_SAMPLE_REGS_ABI_SIMD is set by default on platforms with SIMD
> support, the reclaimed register space means name_to_perf_reg_mask will now map
> to eGPRs instead of XMM registers. 
>
> If a user runs an existing script that explicitly requests individual XMM
> registers, such as perf record -I xmm0, won't this branch fail to match the
> string, return an Unknown register warning, and break backward compatibility
> for those CLI options?
The User should run "perf record -I?" or "perf record --user-regs=?" to get
the supported registers before running "perf record -I xmm0".