linux-kernel - Re: [PATCH v4 1/6] x86: move ZMM exclusion list into CPU feature flag

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Message-ID: <20250210210103.GC348261@sol.localdomain>
Date: Mon, 10 Feb 2025 13:01:03 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	x86@...nel.org, linux-block@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>, Keith Busch <kbusch@...nel.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v4 1/6] x86: move ZMM exclusion list into CPU feature flag

On Mon, Feb 10, 2025 at 09:40:30PM +0100, Borislav Petkov wrote:
> On Mon, Feb 10, 2025 at 09:45:35AM -0800, Eric Biggers wrote:
> > @@ -1598,11 +1578,11 @@ static int __init register_avx_algs(void)
> >  					 ARRAY_SIZE(aes_gcm_algs_vaes_avx10_256),
> >  					 aes_gcm_simdalgs_vaes_avx10_256);
> >  	if (err)
> >  		return err;
> >  
> > -	if (x86_match_cpu(zmm_exclusion_list)) {
> > +	if (boot_cpu_has(X86_FEATURE_PREFER_YMM)) {
> 
> s/boot_cpu_has/cpu_feature_enabled/
> 

$ git grep boot_cpu_has arch/x86/crypto | wc -l
87
$ git grep cpu_feature_enabled arch/x86/crypto | wc -l
0

It wouldn't make sense to change just this one.  Should they really all be
changed?

I see that cpu_feature_enabled() uses code patching while boot_cpu_has() does
not.  All these checks occur once at module load time, though, so code patching
wouldn't be beneficial.

- Eric