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

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Date:   Sun, 17 Apr 2022 09:50:50 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
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 Sun, Apr 17, 2022 at 04:35:58PM +0800, Herbert Xu wrote:
> On Sun, Apr 17, 2022 at 09:31:09AM +0100, Catalin Marinas wrote:
> >
> > Not with my series, the non-sharing of cache lines is preserved.
> > kmalloc() still returns objects aligned to a cache-line.
> > ARCH_DMA_MINALIGN was chosen as the cover-all value for all SoCs
> > supported but I want to reduce the kmalloc() alignment to a cache line
> > size if a platform has a cache line smaller than ARCH_DMA_MINALIGN (most
> > arm64 SoCs have a cache line of 64 bytes rather than 128).
> 
> OK, but then you don't need to play with CRYPTO_MINALIGN at all,
> right? All you need to do is add the padding between the Crypto
> API fields and the context structure, right?

Right, if that's what you prefer. Something like:

diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index 2324ab6f1846..bb645b2f2718 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -645,7 +645,7 @@ struct crypto_tfm {
 	
 	struct crypto_alg *__crt_alg;
 
-	void *__crt_ctx[] CRYPTO_MINALIGN_ATTR;
+	void *__crt_ctx[] __aligned(ARCH_DMA_MINALIGN);
 };

But once we do that, are there any other CRYPTO_MINALIGN left around?

-- 
Catalin