From: Ard Biesheuvel <ardb@kernel.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ben Greear <greearb@candelatech.com>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Eric Biggers <ebiggers@kernel.org>
Subject: Re: [PATCH 0/5] crypto: Implement cmac based on cbc skcipher
Date: Thu, 20 Aug 2020 09:48:02 +0200 [thread overview]
Message-ID: <CAMj1kXHAo8LzKZd9cuwhZzP3ikYr1Bd_zjrnBRDrAU8M=92RWQ@mail.gmail.com> (raw)
In-Reply-To: <20200820074414.GA21848@gondor.apana.org.au>
On Thu, 20 Aug 2020 at 09:44, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Thu, Aug 20, 2020 at 09:33:21AM +0200, Ard Biesheuvel wrote:
> >
> > > On my machine the performance difference on a 1472-byte request
> > > between SIMD and generic is 2161 vs. 7558 (cycles).
> >
> > Sure. But your machine does not have the pathological FPU
> > preserve/restore performance.
>
> Why does that matter? These are numbers for cbc-aesni which means
> just a single preserve/restore for the whole request.
>
No, that is the whole problem. The CCM template has a CBCMAC
implementation that wraps the bare cipher, which means it invokes
crypto_cipher_encrypt_one() for each 16 bytes of input, and each of
those calls involves a FPU preserve/restore.
> Or are you saying on Ben's machine cbc-aesni would have worse
> performance vs. aes-generic?
>
Yes, given the pathological overhead of FPU preserve/restore for every
block of 16 bytes processed by the cbcmac wrapper.
> > The mac80211 CCMP code uses a synchronous ccm aead, which gets backed
> > by a skcipher+ahash combo by the ccm template. So a synchronous ahash
> > is fine for this particular case.
>
> OK I was just grepping for cmac so didn't see this.
>
> For this case, I think it's even more important that it be converted
> over to async because its sending path is also in user context just
> like IPsec.
>
Indeed.
cmac() is not really relevant for performance, afaict. Only cbcmac()
is used for bulk data.
> So simply by sending wireless packets you can hog the CPU while
> doing SIMD in kernel context which would then kill the receive
> path if you're using the generic fallback.
>
> Cheers,
> --
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2020-08-20 7:48 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-02 9:06 [PATCH] crypto: x86/aesni - implement accelerated CBCMAC, CMAC and XCBC shashes Ard Biesheuvel
2020-08-03 19:11 ` Ben Greear
2020-08-04 12:55 ` Ard Biesheuvel
2020-08-04 13:01 ` Ben Greear
2020-08-04 13:08 ` Ard Biesheuvel
2020-08-04 13:22 ` Ben Greear
2020-08-04 19:45 ` Ben Greear
2020-08-04 20:12 ` Ard Biesheuvel
2020-09-23 11:03 ` Ben Greear
2020-10-29 16:58 ` Ard Biesheuvel
2020-08-18 8:24 ` [PATCH 0/5] crypto: Implement cmac based on cbc skcipher Herbert Xu
2020-08-18 8:25 ` [PATCH 1/6] crypto: skcipher - Add helpers for sync skcipher spawn Herbert Xu
2020-08-18 8:25 ` [PATCH 2/6] crypto: ahash - Add helper to free single spawn instance Herbert Xu
2020-08-18 8:25 ` [PATCH 3/6] crypto: ahash - Add init_tfm/exit_tfm Herbert Xu
2020-08-18 8:25 ` [PATCH 4/6] crypto: ahash - Add ahash_alg_instance Herbert Xu
2020-08-18 8:25 ` [PATCH 5/6] crypto: ahash - Remove AHASH_REQUEST_ON_STACK Herbert Xu
2020-08-26 10:55 ` Ard Biesheuvel
2020-08-18 8:25 ` [PATCH 6/6] crypto: cmac - Use cbc skcipher instead of raw cipher Herbert Xu
2020-08-24 9:47 ` Ard Biesheuvel
2020-08-24 11:20 ` Herbert Xu
2020-08-18 8:31 ` [PATCH 0/5] crypto: Implement cmac based on cbc skcipher Ard Biesheuvel
2020-08-18 13:51 ` Herbert Xu
2020-08-18 13:56 ` Ben Greear
2020-08-18 14:05 ` Herbert Xu
2020-08-18 14:17 ` Ben Greear
2020-08-18 22:15 ` Herbert Xu
2020-08-18 22:27 ` Herbert Xu
2020-08-18 22:31 ` Ben Greear
2020-08-18 22:33 ` Herbert Xu
2020-08-18 22:39 ` Ben Greear
2020-08-20 6:58 ` Ard Biesheuvel
2020-08-20 7:01 ` Herbert Xu
2020-08-20 7:04 ` Ard Biesheuvel
2020-08-20 7:06 ` Herbert Xu
2020-08-20 7:19 ` Ard Biesheuvel
2020-08-20 7:29 ` Herbert Xu
2020-08-20 7:33 ` Ard Biesheuvel
2020-08-20 7:44 ` Herbert Xu
2020-08-20 7:48 ` Ard Biesheuvel [this message]
2020-08-20 7:53 ` Herbert Xu
2020-08-20 7:56 ` Ard Biesheuvel
2020-08-20 13:54 ` Ben Greear
2020-08-20 20:10 ` Herbert Xu
2020-08-20 22:09 ` Ben Greear
2020-08-20 22:12 ` Herbert Xu
2020-08-22 22:35 ` Christian Lamparter
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