Messages in this thread | | | Subject | Re: [RFC PATCH V3 08/11] swiotlb: Add bounce buffer remap address setting function | From | Tianyu Lan <> | Date | Mon, 14 Jun 2021 21:42:00 +0800 |
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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.
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