Hi Christoph:
Thanks a lot for your review. There are some reasons.
1) Vmbus drivers don't use DMA API now.
2) Hyper-V Vmbus channel ring buffer already play bounce buffer
role for most vmbus drivers. Just two kinds of packets from
netvsc/storvsc are uncovered.
3) In AMD SEV-SNP based Hyper-V guest, the access physical address
of shared memory should be bounce buffer memory physical address plus
with a shared memory boundary(e.g, 48bit) reported Hyper-V CPUID. It's
called virtual top of memory(vTom) in AMD spec and works as a watermark.
So it needs to ioremap/memremap the associated physical address above
the share memory boundary before accessing them. swiotlb_bounce() uses
low end physical address to access bounce buffer and this doesn't work
in this senario. If something wrong, please help me correct me.
Thanks.
On 3/1/2021 2:54 PM, Christoph Hellwig wrote:
This should be handled by the DMA mapping layer, just like for native
SEV support.
