Re: per-device dma_map_ops for intel-iommu?

David Woodhouse
2019-04-09T14:04:05Z

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On Tue, 2019-04-09 at 15:59 +0200, Christoph Hellwig wrote:
> Hi David and Joerg,
>
> 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?
>
> 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 — and retpolines, which I think you already dealt with — no, no
good reason that I recall.

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