On 12/12/21 11:14 PM, Tianyu Lan wrote:

In Isolation VM with AMD SEV, bounce buffer needs to be accessed via
extra address space which is above shared_gpa_boundary (E.G 39 bit
address line) reported by Hyper-V CPUID ISOLATION_CONFIG. The access
physical address will be original physical address + shared_gpa_boundary.
The shared_gpa_boundary in the AMD SEV SNP spec is called virtual top of
memory(vTOM). Memory addresses below vTOM are automatically treated as
private while memory above vTOM is treated as shared.

This seems to be independently reintroducing some of the SEV
infrastructure.  Is it really OK that this doesn't interact at all with
any existing SEV code?

For instance, do we need a new 'swiotlb_unencrypted_base', or should
this just be using sme_me_mask somehow?