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From: Ard Biesheuvel <ardb@kernel.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	 herbert@gondor.apana.org.au, will@kernel.org,
	kernel-team@android.com
Subject: Re: [PATCH v5 4/5] crypto: arm64/aes-ccm - remove non-SIMD fallback path
Date: Wed, 26 May 2021 11:12:27 +0200	[thread overview]
Message-ID: <CAMj1kXF-t6JHU_8qKekSNf8W5yrTc8Xdk8_hFnMRDm3iU7nG5w@mail.gmail.com> (raw)
In-Reply-To: <YKwf9wmioRxrKOGO@gmail.com>

On Mon, 24 May 2021 at 23:51, Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Fri, May 21, 2021 at 12:20:52PM +0200, Ard Biesheuvel wrote:
> > AES/CCM on arm64 is implemented as a synchronous AEAD, and so it is
> > guaranteed by the API that it is only invoked in task or softirq
> > context. Since softirqs are now only handled when the SIMD is not
> > being used in the task context that was interrupted to service the
> > softirq, we no longer need a fallback path. Let's remove it.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  arch/arm64/crypto/aes-ce-ccm-core.S |   1 +
> >  arch/arm64/crypto/aes-ce-ccm-glue.c | 181 ++++++--------------
> >  2 files changed, 53 insertions(+), 129 deletions(-)
>
> This doesn't just remove the no-SIMD fallback, but it also does some
> refactoring.  Notably, it starts to process all the authenticated data in one
> kernel_neon_begin() / kernel_neon_end() pair rather than many.  Can you explain
> why that is okay now when previously it wasn't, and also split this into two
> separate commits?
>

OK.

For the record, the reason is that, even though kernel_neon_begin/end
are reasonably cheap these days, the common case for CCM (given its
use in networking context) is for the auth/encrypt/finalize routines
to each be called a single time, without any potentially sleeping
calls into the skcipher walk layer in between. Now that we are doing
more work in there (disable softirq processing as well as preemption),
it was a suitable occasion to do some refactoring that I have had on
my list for a while now.

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  reply	other threads:[~2021-05-26 11:06 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-21 10:20 [PATCH v5 0/5] running kernel mode SIMD with softirqs disabled Ard Biesheuvel
2021-05-21 10:20 ` [PATCH v5 1/5] crypto: arm64/gcm-aes-ce - remove non-SIMD fallback path Ard Biesheuvel
2021-05-24 21:46   ` Eric Biggers
2021-05-21 10:20 ` [PATCH v5 2/5] crypto: arm64/aes-neonbs - stop using SIMD helper for skciphers Ard Biesheuvel
2021-05-24 21:46   ` Eric Biggers
2021-05-21 10:20 ` [PATCH v5 3/5] crypto: arm64/aes-ce " Ard Biesheuvel
2021-05-24 21:47   ` Eric Biggers
2021-05-21 10:20 ` [PATCH v5 4/5] crypto: arm64/aes-ccm - remove non-SIMD fallback path Ard Biesheuvel
2021-05-24 21:51   ` Eric Biggers
2021-05-26  9:12     ` Ard Biesheuvel [this message]
2021-05-21 10:20 ` [PATCH v5 5/5] crypto: arm64/aes-ccm - avoid by-ref argument for ce_aes_ccm_auth_data Ard Biesheuvel
2021-05-24 21:53   ` Eric Biggers
2021-05-26  9:14     ` Ard Biesheuvel

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