linux-kernel - Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC

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Message-ID: <YlkV7NtatO7KFusX@gondor.apana.org.au>
Date:   Fri, 15 Apr 2022 14:51:24 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Ard Biesheuvel <ardb@...nel.org>, Will Deacon <will@...nel.org>,
        Marc Zyngier <maz@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of
 ARCH_KMALLOC_MINALIGN

On Wed, Apr 13, 2022 at 09:47:29AM +0100, Catalin Marinas wrote:
>
> With my series, there is no change to the value of CRYPTO_MINALIGN for
> arm64 or any other architecture, so point 3 is unaffected. The series
> does change the kmalloc() alignment and that may be smaller than
> CRYPTO_MINALIGN but neither of points 1 or 2 above are affected since
> (a) we still have a sufficiently large ARCH_KMALLOC_MINALIGN of 64 and
> (b) the kmalloc'ed buffers are safe for non-coherent DMA.
> 
> Herbert, Ard, if I missed anything please let me know but based on my
> understanding, this series is safe for the crypto code.

Sorry, but you can't change CRYPTO_MINALIGN to a value greater
than the minimum alignment returned by kmalloc.  That simply
doesn't work.  There is no magic in the Crypto API that makes
this work.

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