linux-kernel - Re: [PATCH v4 10/24] crypto: x86/poly

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Message-ID: <Y4CExnFX46mk4/1+@gondor.apana.org.au>
Date:   Fri, 25 Nov 2022 17:03:02 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Robert Elliott <elliott@....com>, davem@...emloft.net,
        tim.c.chen@...ux.intel.com, ap420073@...il.com,
        David.Laight@...lab.com, ebiggers@...nel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/24] crypto: x86/poly - limit FPU preemption

On Fri, Nov 25, 2022 at 09:59:17AM +0100, Ard Biesheuvel wrote:
>
> On arm64, this is implemented in an assembler macro 'cond_yield' so we
> don't need to preserve/restore the SIMD state state at all if the
> yield is not going to result in a call to schedule(). For example, the
> SHA3 code keeps 400 bytes of state in registers, which we don't want
> to save and reload unless needed. (5f6cb2e617681 'crypto:
> arm64/sha512-ce - simplify NEON yield')

Yes this would be optimally done from the assembly code which
would make a difference if they benefited from larger block sizes.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt