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 v6 5/6] crypto: arm64/aes-ccm - reduce NEON begin/end calls for common case
Date: Wed, 26 May 2021 20:08:05 +0200 [thread overview]
Message-ID: <CAMj1kXFKPB12QtP__7ANN5n-SFvmrskoCN2zwe-pXD_0HPrnBQ@mail.gmail.com> (raw)
In-Reply-To: <YK6B4PDchHbXNx3U@gmail.com>
On Wed, 26 May 2021 at 19:14, Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Wed, May 26, 2021 at 12:07:28PM +0200, Ard Biesheuvel wrote:
> > AES-CCM (as used in WPA2 CCMP, for instance) typically involves
> > authenticate-only data, and operates on a single network packet, and so
> > the common case is for the authenticate, en/decrypt and finalize SIMD
> > helpers to all be called exactly once in sequence. Since
> > kernel_neon_end() now involves manipulation of the preemption state as
> > well as the softirq mask state, let's reduce the number of times we are
> > forced to call it to only once if we are handling this common case.
> >
> > 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 | 74 +++++++++++---------
> > 2 files changed, 43 insertions(+), 32 deletions(-)
> >
> > diff --git a/arch/arm64/crypto/aes-ce-ccm-core.S b/arch/arm64/crypto/aes-ce-ccm-core.S
> > index 99a028e298ed..8adff299fcd3 100644
> > --- a/arch/arm64/crypto/aes-ce-ccm-core.S
> > +++ b/arch/arm64/crypto/aes-ce-ccm-core.S
> > @@ -124,6 +124,7 @@ SYM_FUNC_START(ce_aes_ccm_final)
> > SYM_FUNC_END(ce_aes_ccm_final)
> >
> > .macro aes_ccm_do_crypt,enc
> > + cbz x2, 5f
> > ldr x8, [x6, #8] /* load lower ctr */
> > ld1 {v0.16b}, [x5] /* load mac */
> > CPU_LE( rev x8, x8 ) /* keep swabbed ctr in reg */
> > diff --git a/arch/arm64/crypto/aes-ce-ccm-glue.c b/arch/arm64/crypto/aes-ce-ccm-glue.c
> > index 54bd2494a000..98159f2c49ae 100644
> > --- a/arch/arm64/crypto/aes-ce-ccm-glue.c
> > +++ b/arch/arm64/crypto/aes-ce-ccm-glue.c
> > @@ -97,10 +97,8 @@ static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen)
> > static void ccm_update_mac(struct crypto_aes_ctx *key, u8 mac[], u8 const in[],
> > u32 abytes, u32 *macp)
> > {
> > - kernel_neon_begin();
> > ce_aes_ccm_auth_data(mac, in, abytes, macp, key->key_enc,
> > num_rounds(key));
> > - kernel_neon_end();
> > }
> [...]
> > + if (req->assoclen)
> > + ccm_calculate_auth_mac(req, mac);
> > +
>
> This still makes all the associated data be processed under a single
> kernel_neon_begin() / kernel_neon_end() pair, even if there is a large amount of
> it. Shouldn't it be limited to a reasonable amount at a time, like 4K?
> This sort of thing has been considered a bug before, e.g. see
> commit 706024a52c6 ("crypto: arch/lib - limit simd usage to 4k chunks").
>
> You could do the entire CCM operation under a single pair as long as there isn't
> more than 4K of associated data.
>
Good point. I'll add a separate patch for that.
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next prev parent reply other threads:[~2021-05-26 19:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-26 10:07 [PATCH v6 0/6] running kernel mode SIMD with softirqs disabled Ard Biesheuvel
2021-05-26 10:07 ` [PATCH v6 1/6] crypto: arm64/gcm-aes-ce - remove non-SIMD fallback path Ard Biesheuvel
2021-05-26 10:07 ` [PATCH v6 2/6] crypto: arm64/aes-neonbs - stop using SIMD helper for skciphers Ard Biesheuvel
2021-05-26 10:07 ` [PATCH v6 3/6] crypto: arm64/aes-ce " Ard Biesheuvel
2021-05-26 10:07 ` [PATCH v6 4/6] crypto: arm64/aes-ccm - remove non-SIMD fallback path Ard Biesheuvel
2021-05-26 16:57 ` Eric Biggers
2021-05-26 10:07 ` [PATCH v6 5/6] crypto: arm64/aes-ccm - reduce NEON begin/end calls for common case Ard Biesheuvel
2021-05-26 17:14 ` Eric Biggers
2021-05-26 18:08 ` Ard Biesheuvel [this message]
2021-05-26 10:07 ` [PATCH v6 6/6] crypto: arm64/aes-ccm - avoid by-ref argument for ce_aes_ccm_auth_data Ard Biesheuvel
2021-05-26 17:18 ` Eric Biggers
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