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

[Tianyu Lan]

On 7/21/2021 10:33 PM, Christoph Hellwig wrote:
> 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?

Current vmbus device drivers don't use dma_alloc_attrs/dma_alloc
_coherent() because vmbus driver allocates ring buffer for all devices. 
Ring buffer has been marked decrypted and remapped in vmbus driver. 
Netvsc and storvsc drivers just need to use  dma_map_single/dma_map_page().