Re: [RFC PATCH V3 08/11] swiotlb: Add bounce buffer remap address setting function

[Tianyu Lan]

On 6/14/2021 9:37 PM, Tianyu Lan wrote:
> On 6/14/2021 3:12 PM, Christoph Hellwig wrote:
> > On Mon, Jun 07, 2021 at 10:56:47PM +0800, Tianyu Lan wrote:
> > > These addresses in extra address space works as system memory mirror. 
> > > The
> > > shared memory with host in Isolation VM needs to be accessed via extra
> > > address space which is above shared gpa boundary.
> >
> > Why?
>
> 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. Using vTOM to
> separate memory in this way avoids the need to augment the standard x86
> page tables with C-bit markings, simplifying guest OS software.

Here is the spec link and vTOM description is in the page 14.
https://www.amd.com/system/files/TechDocs/SEV-SNP-strengthening-vm-isolation-with-integrity-protection-and-more.pdf

Thanks.