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Re: consolidate direct dma mapping and swiotlb support

To: Christoph Hellwig <>,
Subject: Re: consolidate direct dma mapping and swiotlb support
From: Vladimir Murzin <>
Date: Fri, 29 Dec 2017 10:52:14 +0000
Cc:,,,, Guan Xuetao <>,,,,,,,,,,,, Michal Simek <>,,,,,
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On 29/12/17 08:18, Christoph Hellwig wrote:
> Almost every architecture supports a direct dma mapping implementation,
> where no iommu is used and the device dma address is a 1:1 mapping to
> the physical address or has a simple linear offset.  Currently the
> code for this implementation is most duplicated over the architectures,
> and the duplicated again in the swiotlb code, and then duplicated again
> for special cases like the x86 memory encryption DMA ops.
> This series takes the existing very simple dma-noop dma mapping
> implementation, enhances it with all the x86 features and quirks, and
> creates a common set of architecture hooks for it and the swiotlb code.
> It then switches a large number of architectures to this generic
> direct map implement and the new generic swiotlb dma_map ops.
> Note that for now this only handles architectures that do cache coherent
> DMA, but a similar consolidation for non-coherent architectures is in the
> work for later merge windows.

Is it available in your dma-mapping.git or somewhere else?


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