linux-kernel - Re: [tip: perf/urgent] x86/cpufeatures: Add dedicated feature word for CPUID leaf 0x80000022[EAX]

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Message-ID: <20240319130054.GCZfmMhp-7Qa0eDaTC@fat_crate.local>
Date: Tue, 19 Mar 2024 14:00:54 +0100
From: Borislav Petkov <bp@...en8.de>
To: Sandipan Das <sandipan.das@....com>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>, x86@...nel.org
Subject: Re: [tip: perf/urgent] x86/cpufeatures: Add dedicated feature word
 for CPUID leaf 0x80000022[EAX]

On Tue, Mar 19, 2024 at 10:36:01AM -0000, tip-bot2 for Sandipan Das wrote:
> The following commit has been merged into the perf/urgent branch of tip:
> 
> Commit-ID:     f0a22ea644717fa21698a32d342fcd307e53a935
> Gitweb:        https://git.kernel.org/tip/f0a22ea644717fa21698a32d342fcd307e53a935
> Author:        Sandipan Das <sandipan.das@....com>
> AuthorDate:    Tue, 19 Mar 2024 13:48:16 +05:30
> Committer:     Ingo Molnar <mingo@...nel.org>
> CommitterDate: Tue, 19 Mar 2024 11:23:47 +01:00
> 
> x86/cpufeatures: Add dedicated feature word for CPUID leaf 0x80000022[EAX]
> 
> Move the existing scattered performance monitoring related feature bits
> from CPUID leaf 0x80000022[EAX] into a dedicated word since additional
> bits will be defined from the same leaf in the future. This includes
> X86_FEATURE_PERFMON_V2 and X86_FEATURE_AMD_LBR_V2.

That CPUID leaf has a whopping three bits defined and the rest is
reserved. You should do a dedicated leaf when we use at least 50% of the
bits in the leaf. But not like this.

Please do simply another synthetic leaf and put your bits there.

Thx.

-- 
Regards/Gruss,
    Boris.

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