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Date:   Thu, 20 Aug 2020 17:01:42 +1000
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
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On Thu, Aug 20, 2020 at 08:58:15AM +0200, Ard Biesheuvel wrote:
>
> But if we look at the actual issue at hand, we might also look into
> amortizing the FPU preserve/restore over multiple invocations of a
> cipher. I proposed a patch a while ago that makes cipher an internal
> crypto API abstraction, and we could easily add pre/post hooks that
> preserve/restore the FPU in this case, in which case we would not need
> any changes at higher levels.

I think any use of SIMD crypto_cipher on bulk data is just wrong.
Because the performance degradation when SIMD cannot be used is
too great for this to make sense.

So optimising the FPU overhead is attacking the wrong problem.

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