From: Herbert Xu <herbert@gondor.apana.org.au>
To: Ard Biesheuvel <ardb@kernel.org>
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 17:29:10 +1000 [thread overview]
Message-ID: <20200820072910.GA21631@gondor.apana.org.au> (raw)
In-Reply-To: <CAMj1kXE6QDxjNKSpzTrxe+QU0DF9CYp-W7bGe1AyFzYHOJQ41Q@mail.gmail.com>
On Thu, Aug 20, 2020 at 09:19:16AM +0200, Ard Biesheuvel wrote:
>
> Actually, I'm not so sure that they will be so much worse. The
> expensive FPU preserve/restore occurs for every 16 bytes of data
> processed by the AES cipher, which I'd estimate to take ~10 cycles per
> byte for an unaccelerated implementation. But table based AES should
> be avoided, especially for MAC algorithms where the plaintext may be
> known to an attacker who is after the key.
On my machine the performance difference on a 1472-byte request
between SIMD and generic is 2161 vs. 7558 (cycles).
>
> However, the CCMP handling is invoked from softirq context or from
> task context, and so SIMD is generally available unless the softirq
> happens to be taken over the back of a hardirq that interrupted a task
> running in the kernel that was using the SIMD already. IOW, this
> happens so rarely in practice that I would not expect it to be
> noticeable in the performance stats.
What if the same machine was doing TLS/IPsec sends at full throttle?
That would be exactly the wrong time to slow down softirqs four-fold,
no?
> My v2 attempt at cbcmac(aesni) implements an ahash, but a synchronous
> one. This means we can amortize the FPU preserve/restore over the
> entire scatterlist, instead of relying on the ahash walk to present
> the data in virtually mapped chunks.
>
> I'd still like to explore this approach, but I simply haven't had the
> spare cycles to spend on this.
I don't have an issue your patch per se. But please make it so that
it has the async path like everything else. Also wireless uses shash
so it can't use an ahash anyway even if it is sync.
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 7:29 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 [this message]
2020-08-20 7:33 ` Ard Biesheuvel
2020-08-20 7:44 ` Herbert Xu
2020-08-20 7:48 ` Ard Biesheuvel
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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