On 2021-06-07 07:43, Christoph Hellwig wrote:

On Sun, May 30, 2021 at 11:06:25AM -0400, Tianyu Lan wrote:

quoted

From: Tianyu Lan <redacted>

For Hyper-V isolation VM with AMD SEV SNP, the bounce buffer(shared memory)
needs to be accessed via extra address space(e.g address above bit39).
Hyper-V code may remap extra address space outside of swiotlb. swiotlb_
bounce() needs to use remap virtual address to copy data from/to bounce
buffer. Add new interface swiotlb_set_bounce_remap() to do that.

Why can't you use the bus_dma_region ranges to remap to your preferred
address?

FWIW, I think a better generalisation for this would be allowing 
set_memory_decrypted() to return an address rather than implicitly 
operating in-place, and hide all the various hypervisor hooks behind that.

Robin.