linux-kernel - Re: [NEEDS-REVIEW] [RFC PATCH 7/8] crypto: x86/aes-kl - Support AES algorithm using Key Locker instructions

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Date:   Fri, 18 Dec 2020 10:56:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     "Chang S. Bae" <chang.seok.bae@...el.com>, tglx@...utronix.de,
        mingo@...nel.org, bp@...e.de, luto@...nel.org, x86@...nel.org,
        herbert@...dor.apana.org.au, dan.j.williams@...el.com,
        ravi.v.shankar@...el.com, ning.sun@...el.com,
        kumar.n.dwarakanath@...el.com, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [NEEDS-REVIEW] [RFC PATCH 7/8] crypto: x86/aes-kl - Support AES
 algorithm using Key Locker instructions

On Thu, Dec 17, 2020 at 12:58:34PM -0800, Dave Hansen wrote:
> On 12/16/20 9:41 AM, Chang S. Bae wrote:
> > +config CRYPTO_AES_KL
> > +	tristate "AES cipher algorithms (AES-KL)"
> > +	depends on X86_KEYLOCKER
> > +	select CRYPTO_AES_NI_INTEL
> > +	help
> > +	  Use AES Key Locker instructions for AES algorithm.
> > +
> > +	  AES cipher algorithms (FIPS-197). AES uses the Rijndael
> > +	  algorithm.
> > +
> > +	  Rijndael appears to be consistently a very good performer in both
> > +	  hardware and software across a wide range of computing
> > +	  environments regardless of its use in feedback or non-feedback
> > +	  modes. Its key setup time is excellent, and its key agility is
> > +	  good. Rijndael's very low memory requirements make it very well
> > +	  suited for restricted-space environments, in which it also
> > +	  demonstrates excellent performance. Rijndael's operations are
> > +	  among the easiest to defend against power and timing attacks.
> > +
> > +	  The AES specifies three key sizes: 128, 192 and 256 bits
> > +
> > +	  See <http://csrc.nist.gov/encryption/aes/> for more information.
> > +

It's direct copy-pasta from CRYPTO_AES_NI_INTEL until about here.

> > +	  For 128- and 256-bit keys, the AES cipher algorithm is
> > +	  implemented by AES Key Locker instructions. This implementation
> > +	  does not need an AES key once wrapped to an encoded form. For AES
> > +	  compliance, 192-bit is processed by AES-NI instructions.
> 
> Giving a history lesson and high-level overview of AES doesn't quite
> seem appropriate here, unless this is the first the kernel has seen of AES.

And the new bits aren't really enlightening either, as you point out.