linux-kernel - Re: [RFC PATCH] crypto: flush poison data

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Message-ID: <YsU4/qrnxG8yjFwC@Red>
Date:   Wed, 6 Jul 2022 09:25:50 +0200
From:   LABBE Corentin <clabbe@...libre.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Ben Dooks <ben.dooks@...ethink.co.uk>, herbert@...dor.apana.org.au,
        heiko@...ech.de, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev
Subject: Re: [RFC PATCH] crypto: flush poison data

Le Tue, Jul 05, 2022 at 07:58:34PM +0200, Christoph Hellwig a écrit :
> On Tue, Jul 05, 2022 at 07:56:11PM +0200, LABBE Corentin wrote:
> > My problem is that a dma_sync on the data buffer corrupt the poison buffer as collateral dommage.
> > Probably because the sync operate on a larger region than the requested dma_sync length.
> > So I try to flush poison data in the cryptoAPI.
> 
> Data structures that are DMAed to must be aligned to
> the value returned by dma_get_cache_alignment(), as non-coherent DMA
> by definition can disturb the data inside that boundary.  That is not
> a bug but fundamentally part of how DMA works when the device attachment
> is not cache coherent.

I am sorry but I dont see how this can help my problem.