# Re: \[PATCH V3 10/13\] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM

- From: Christoph Hellwig \<hch@lst.de\>
- Date: 2021-08-19 08:50:08 
- List: linux-arch
- Page: https://ratatoskr.run/linux-arch/2021/08/1482650
- Thread: https://ratatoskr.run/xen-devel/2021/08/1472230/t.md

```text
On Mon, Aug 16, 2021 at 10:50:26PM +0800, Tianyu Lan wrote:
> Hi Christoph:
>       Sorry to bother you.Please double check with these two patches
> " [PATCH V3 10/13] x86/Swiotlb: Add Swiotlb bounce buffer remap function 
> for HV IVM" and "[PATCH V3 09/13] DMA: Add dma_map_decrypted/dma_
> unmap_encrypted() function".

Do you have a git tree somewhere to look at the whole tree?

>       The swiotlb bounce buffer in the isolation VM are allocated in the
> low end memory and these memory has struct page backing. All dma address
> returned by swiotlb/DMA API are low end memory and this is as same as what 
> happen in the traditional VM.

Indeed.

>       The API dma_map_decrypted() introduced in the patch 9 is to map the 
> bounce buffer in the extra space and these memory in the low end space are 
> used as DMA memory in the driver. Do you prefer these APIs
> still in the set_memory.c? I move the API to dma/mapping.c due to the
> suggested name arch_dma_map_decrypted() in the previous mail
> (https://lore.kernel.org/netdev/20210720135437.GA13554@lst.de/).

Well, what would help is a clear description of the semantics.
```