Re: [Resend RFC PATCH V4 09/13] x86/Swiotlb/HV: Add Swiotlb bounce buffer remap function for HV IVM

From: Christoph Hellwig
Date: Wed Jul 21 2021 - 10:34:05 EST

On Wed, Jul 21, 2021 at 06:28:48PM +0800, Tianyu Lan wrote:
> dma_mmap_attrs() and dma_get_sgtable_attrs() get input virtual address
> belonging to backing memory with struct page and returns bounce buffer
> dma physical address which is below shared_gpa_boundary(vTOM) and passed
> to Hyper-V via vmbus protocol.
> The new map virtual address is only to access bounce buffer in swiotlb
> code and will not be used other places. It's stored in the mem->vstart.
> So the new API set_memory_decrypted_map() in this series is only called
> in the swiotlb code. Other platforms may replace set_memory_decrypted()
> with set_memory_decrypted_map() as requested.

It seems like you are indeed not using these new helpers in
dma_direct_alloc. How is dma_alloc_attrs/dma_alloc_coherent going to
work on these systems?