linux-kernel - Re: [PATCH] crypto: x86/chacha

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Message-ID: <20250407164842.GC2536@sol.localdomain>
Date: Mon, 7 Apr 2025 09:48:42 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Ard Biesheuvel <ardb@...nel.org>, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	"Jason A. Donenfeld" <Jason@...c4.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] crypto: x86/chacha - Remove SIMD fallback path

On Thu, Apr 03, 2025 at 12:14:50PM +0800, Herbert Xu wrote:
> On Wed, Apr 02, 2025 at 08:59:34PM -0700, Eric Biggers wrote:
> >
> > But in a lot of cases there is also no reason to even add that restriction.  I'm
> > not sure why you're so eager to make the library functions harder to use.
> 
> I have no intention of making any changes to siphash.  It doesn't
> even use SIMD.
> 
> All I want to do is get rid of the crypto_simd_usable() fallback
> paths that we currently have in arch/x86/crypto.  This code is
> never used in hardirq context (and should never be).
> 
> For example:
> 
> ---8<---
> Get rid of the fallback path as SIMD is now always usable in softirq
> context.
> 
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
> 

It looks like this broken patch already got applied for some reason.

First, there doesn't seem to be agreement yet that the library functions should
have requirements on the calling context.

Second, your patch made unrelated changes that deleted the checks for SSSE3
support.  Thus dropping support for CPUs that don't support SSSE3.

- Eric