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Message-ID: <b491bb987c8cc3f95328d33586ec25c497cc8b8b.camel@infradead.org>
Subject: Re: per-device dma_map_ops for intel-iommu?
From:   David Woodhouse <dwmw2@infradead.org>
To:     Christoph Hellwig <hch@lst.de>, Joerg Roedel <joro@8bytes.org>
Cc:     iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Date:   Tue, 09 Apr 2019 17:03:52 +0300
In-Reply-To: <20190409135924.GA11431@lst.de>
References: <20190409135924.GA11431@lst.de>
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On Tue, 2019-04-09 at 15:59 +0200, Christoph Hellwig wrote:
> Hi David and Joerg,
>=20
> do you remember a good reason why intel-iommu is not using per-device
> dma_map_ops like the AMD iommu or the various ARM iommus?
>=20
> Right now intel-iommu.c contains a half-asses reimplementation of the
> dma direct code for the iommu_no_mapping() case, and it would seem
> much nicer to just fall back to that case and not even call into
> intel-iommu in that case.

Other than the complexities about passthrough mode and various "oh shit
we forgot to actually test that iommu+gfx actually works before
shipping hardware" type of quirks that bypass the IOMMU for certain
devices =E2=80=94 and retpolines, which I think you already dealt with =E2=
=80=94 no, no
good reason that I recall.

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