linux-kernel - Re: [PATCH] x86/cpufeatures: Move the definition of X86_FEATURE_AMX

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Message-ID: <47362220-30d5-c513-a2aa-61187ee91c41@redhat.com>
Date:   Tue, 18 Jan 2022 18:15:29 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Like Xu <like.xu.linux@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Jing Liu <jing2.liu@...el.com>, linux-kernel@...r.kernel.org,
        "Bae, Chang Seok" <chang.seok.bae@...el.com>
Subject: Re: [PATCH] x86/cpufeatures: Move the definition of X86_FEATURE_AMX_*
 to the word 18

On 1/18/22 18:11, Dave Hansen wrote:
> What tree is this against?  I see BF16 and INT8 in some old versions of
> Chang's patches, but not current kernels.  All I see right now in
> tip/master is:
> 
>> #define X86_FEATURE_AMX_TILE            (18*32+24) /* AMX tile ...
> 
> It's still in the wrong spot, but the other two features aren't there.

It was added for the KVM side of AMX (commit 690a757d610e, "kvm: x86: 
Add CPUID support for Intel AMX") and is in Linus's tree.

Paolo


>> We have defined the word 18 for Intel-defined CPU features from CPUID level> 0x00000007:0 (EDX). Let's move the definitions of X86_FEATURE_AMX_* to
> the> right entry to prevent misinterpretation. No functional change
> intended.
> Please, no "we's" in changelogs.  Don't say, "let's move".  Just say:
> "Move..."
> 
> The subject could probably also be trimmed a bit.  Perhaps:
> 
> 	x86/cpu: Move AMX CPU feature defines to correct word location
> 
>