linux-kernel - Re: [PATCH v2 3/3] crypto: lib - move crypto_simd_disabled_for

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Message-ID: <YtY0T4qASnYOIjIW@sol.localdomain>
Date:   Mon, 18 Jul 2022 21:34:23 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] crypto: lib - move crypto_simd_disabled_for_test
 into utils

On Sat, Jul 16, 2022 at 08:32:55PM +0200, Jason A. Donenfeld wrote:
> Hi Eric,
> 
> On Fri, Jul 15, 2022 at 11:29:20PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> > 
> > Move the definition of crypto_simd_disabled_for_test into
> > lib/crypto/utils.c so that it can be accessed by library code.
> > 
> > This is needed when code that is shared between a traditional crypto API
> > implementation and a library implementation is built-in, but
> > CRYPTO_ALGAPI=m.  The x86 blake2s previously was an example of this
> > (https://lore.kernel.org/linux-crypto/20220517033630.1182-1-gaochao49@huawei.com/T/#u).
> > Although that case was resolved by removing the blake2s shash support,
> > this problem could easily come back in the future, so let's address it.
> 
> I'm not sure I see the reason in general for a utility library rather
> than doing these piecemeal like the rest of lib functions. Why is crypto
> special here? But in particular to this patch: nothing is actually using
> crypto_simd_disabled_for_test in lib/crypto, right? So is this
> necessary?

Well, this is what Herbert wanted:
https://lore.kernel.org/r/YtEgzHuuMts0YBCz@gondor.apana.org.au.  It's
subjective, but for now I think I prefer this approach too, since the utility
functions are so small and are widely used.  A whole module is overkill for just
a few lines of code.

The commit message answers your second and third questions.

- Eric