Re: [PATCH v6 5/8] iommu: Add bounce page APIs

[Joerg Roedel]

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?


Regards,

	Joerg