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Date:   Tue, 9 Aug 2022 20:39:13 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Keith Busch <kbusch@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@fb.com>,
        linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
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Subject: Re: [PATCHv3 0/7] dma mapping optimisations
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On Tue, Aug 09, 2022 at 08:18:45AM -0600, Keith Busch wrote:
> On Tue, Aug 09, 2022 at 08:46:13AM +0200, Christoph Hellwig wrote:
> >  - the design seems to ignore DMA ownership.  Every time data in
> >    transfered data needs to be transferred to and from the device,
> >    take a look at Documentation/core-api/dma-api.rst and
> >    Documentation/core-api/dma-api-howto.rst.
> 
> I have this doing appropriate dma_sync_single_for_{device,cpu} if we aren't
> using coherent memory. Is there more to ownership beyond that?

As long as we only every support a single device that is fine, but
if we want to support that it gets complicated.  Sorry, this should
have been integrated with the mumblings on the multiple device mappings
as the statement iѕ false without that.