linux-kernel - Re: [PATCH 15/17] lib/crypto: s390/sha3: Migrate optimized code into library

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Message-ID: <51fc91b6-3a6e-44f7-ae93-aef0bcb48964@linux.ibm.com>
Date: Mon, 20 Oct 2025 16:00:42 +0200
From: Holger Dengler <dengler@...ux.ibm.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: David Howells <dhowells@...hat.com>, Ard Biesheuvel <ardb@...nel.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-crypto@...r.kernel.org
Subject: Re: [PATCH 15/17] lib/crypto: s390/sha3: Migrate optimized code into
 library

On 20/10/2025 02:50, Eric Biggers wrote:
> Instead of exposing the s390-optimized SHA-3 code via s390-specific
> crypto_shash algorithms, instead just implement the sha3_absorb_blocks()
> and sha3_keccakf() library functions.  This is much simpler, it makes
> the SHA-3 library functions be s390-optimized, and it fixes the
> longstanding issue where the s390-optimized SHA-3 code was disabled by
> default.  SHA-3 still remains available through crypto_shash, but
> individual architectures no longer need to handle it.
> 
> Note that the existing code used both CPACF_KIMD_SHA3_224 and
> CPACF_KIMD_SHA3_256 after checking for just CPACF_KIMD_SHA3_256, and
> similarly for 384 and 512.  I've preserved that behavior.
> 
> Signed-off-by: Eric Biggers <ebiggers@...nel.org>
The current code also cover a performance feature, which allows (on supported hardware, e.g. z17) to skip the ICV initialization. The support has been introduced with 88c02b3f79a6 ("s390/sha3: Support sha3 performance enhancements"). Unfortunately, this patch removes this support. Was this intended?

The get this feature back, we need to hook also into the init() function, set the according bit for the first message block and skip the initialization of the ICV.

Please also add me and Harald Freudenberger to the cc: list for this patch.

-- 
Mit freundlichen Grüßen / Kind regards
Holger Dengler
--
IBM Systems, Linux on IBM Z Development
dengler@...ux.ibm.com