On Fri, Apr 8, 2022, at 2:05 PM, Vishal Annapurve wrote: > This series implements selftests targeting the feature floated by Chao > via: > https://lore.kernel.org/linux-mm/20220310140911.50924-1-chao.p.peng@xxxxxxxxxxxxxxx/ > > Below changes aim to test the fd based approach for guest private memory > in context of normal (non-confidential) VMs executing on non-confidential > platforms. > > Confidential platforms along with the confidentiality aware software > stack support a notion of private/shared accesses from the confidential > VMs. > Generally, a bit in the GPA conveys the shared/private-ness of the > access. Non-confidential platforms don't have a notion of private or > shared accesses from the guest VMs. To support this notion, > KVM_HC_MAP_GPA_RANGE > is modified to allow marking an access from a VM within a GPA range as > always shared or private. Any suggestions regarding implementing this ioctl > alternatively/cleanly are appreciated. This is fantastic. I do think we need to decide how this should work in general. We have a few platforms with somewhat different properties: TDX: The guest decides, per memory access (using a GPA bit), whether an access is private or shared. In principle, the same address could be *both* and be distinguished by only that bit, and the two addresses would refer to different pages. SEV: The guest decides, per memory access (using a GPA bit), whether an access is private or shared. At any given time, a physical address (with that bit masked off) can be private, shared, or invalid, but it can't be valid as private and shared at the same time. pKVM (currently, as I understand it): the guest decides by hypercall, in advance of an access, which addresses are private and which are shared. This series, if I understood it correctly, is like TDX except with no hardware security. Sean or Chao, do you have a clear sense of whether the current fd-based private memory proposal can cleanly support SEV and pKVM? What, if anything, needs to be done on the API side to get that working well? I don't think we need to support SEV or pKVM right away to get this merged, but I do think we should understand how the API can map to them.
