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SubjectRe: [PATCH v6 5/8] iommu: Add bounce page APIs
Hi Lu Baolu,

On Tue, Jul 30, 2019 at 12:52:26PM +0800, Lu Baolu wrote:
> * iommu_bounce_map(dev, addr, paddr, size, dir, attrs)
> - Map a buffer start at DMA address @addr in bounce page
> manner. For buffer parts that doesn't cross a whole
> minimal IOMMU page, the bounce page policy is applied.
> A bounce page mapped by swiotlb will be used as the DMA
> target in the IOMMU page table. Otherwise, the physical
> address @paddr is mapped instead.
> * iommu_bounce_unmap(dev, addr, size, dir, attrs)
> - Unmap the buffer mapped with iommu_bounce_map(). The bounce
> page will be torn down after the bounced data get synced.
> * iommu_bounce_sync(dev, addr, size, dir, target)
> - Synce the bounced data in case the bounce mapped buffer is
> reused.

I don't really get why this API extension is needed for your use-case.
Can't this just be done using iommu_map/unmap operations? Can you please
elaborate a bit why these functions are needed?



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