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

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Date:   Mon, 18 Apr 2022 10:19:20 +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 Mon, Apr 18, 2022 at 04:37:17PM +0800, Herbert Xu wrote:
> On Sun, Apr 17, 2022 at 05:30:27PM +0100, Catalin Marinas wrote:
> >
> > Do you mean as per Ard's proposal here:
> > 
> > https://lore.kernel.org/r/CAMj1kXH0x5Va7Wgs+mU1ONDwwsazOBuN4z4ihVzO2uG-n41Kbg@mail.gmail.com
> > 
> > struct crypto_request {
> > 	union {
> > 		struct {
> > 			... fields ...
> > 		};
> > 		u8 __padding[ARCH_DMA_MINALIGN];
> > 	};
> > 	void __ctx[]  __aligned(CRYPTO_MINALIGN);
> > };
> > 
> > If CRYPTO_MINALIGN is lowered to, say, 8 (to be the same as lowest
> > ARCH_KMALLOC_MINALIGN), the __alignof__(req->__ctx) would be 8.
> > Functions like crypto_tfm_ctx_alignment() will return 8 when what you
> > need is 128. We can change those functions to return ARCH_DMA_MINALIGN
> > instead or always bump cra_alignmask to ARCH_DMA_MINALIGN-1.
> 
> OK, at this point I think we need to let the code do the talking :)
> 
> I've seen Ard's patches already and I think I understand what your
> needs are.  So let me whip up some code to show you guys what I
> think needs to be done.
> 
> Please bear with me for a few days.

Thanks Herbert, that's great. Whenever you have time, I'll be busy this
week with collecting arm64 patches for the upcoming merging window
anyway.

-- 
Catalin