linux-kernel - Re: [PATCH v4 1/2] x86/cpufeatures: Add dedicated feature word for CPUID leaf 0x80000022[EAX]

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Date: Tue, 19 Mar 2024 14:00:26 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Sandipan Das <sandipan.das@....com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, peterz@...radead.org, acme@...nel.org,
	namhyung@...nel.org, mark.rutland@....com,
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
	adrian.hunter@...el.com, tglx@...utronix.de, bp@...en8.de,
	seanjc@...gle.com, pbonzini@...hat.com, eranian@...gle.com,
	irogers@...gle.com, ravi.bangoria@....com, ananth.narayan@....com
Subject: Re: [PATCH v4 1/2] x86/cpufeatures: Add dedicated feature word for
 CPUID leaf 0x80000022[EAX]


* Ingo Molnar <mingo@...nel.org> wrote:

> > +/* AMD-defined performance monitoring features, CPUID level 0x80000022 (EAX), word 21 */
> > +#define X86_FEATURE_PERFMON_V2		(21*32+ 0) /* AMD Performance Monitoring Version 2 */
> > +#define X86_FEATURE_AMD_LBR_V2		(21*32+ 1) /* AMD Last Branch Record Extension Version 2 */
> 
> Thank you! I presume you tested both patches on the relevant system 
> with the X86_FEATURE_AMD_LBR_PMC_FREEZE bug?

Also, Boris reminds me that we really want to do what I suggested 
originally and use a new synthethic word here, not a new vendor word, to 
keep all the bits better compressed in cpuinfo.x86_capability[] - so one 
more iteration will be needed.

Thanks,

	Ingo