linux-kernel - Re: [PATCH] crypto: talitos - Remove GFP

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Message-ID: <Y7vEPRYRRpJVcHcQ@gondor.apana.org.au>
Date:   Mon, 9 Jan 2023 15:37:33 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        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>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH] crypto: talitos - Remove GFP_DMA and add DMA alignment
 padding

On Mon, Jan 09, 2023 at 07:18:27AM +0000, Christophe Leroy wrote:
>
> Doesn't GFP_DMA guarantees that the provided memory is addressable for 
> DMA ? Or do we assume that all memory returned by kmalloc can be used 
> for DMA ?

No it does not.  Please refer to the DMI API documentation.

> kmalloc() already returns not DMA aligned memory, why does it becomes a 
> problem now ?

As it stands kmalloc on arm64 returns DMA-aligned memory.  This
will soon no longer be the case.

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