On Wed, 2024-05-15 at 08:49 -0700, Rick Edgecombe wrote: > On Wed, 2024-05-15 at 08:34 -0700, Sean Christopherson wrote: > > On Tue, May 14, 2024, Rick Edgecombe wrote: > > > When virtualizing some CPU features, KVM uses kvm_zap_gfn_range() to zap > > > guest mappings so they can be faulted in with different PTE properties. > > > > > > For TDX private memory this technique is fundamentally not possible. > > > Remapping private memory requires the guest to "accept" it, and also the > > > needed PTE properties are not currently supported by TDX for private > > > memory. > > > > > > These CPU features are: > > > 1) MTRR update > > > 2) CR0.CD update > > > 3) Non-coherent DMA status update > > > > Please go review the series that removes these disaster[*], I suspect it > > would > > literally have taken less time than writing this changelog :-) > > > > [*] https://lore.kernel.org/all/20240309010929.1403984-1-seanjc@xxxxxxxxxx > > We have one additional detail for TDX in that KVM will have different cache > attributes between private and shared. Although implementation is in a later > patch, that detail has an affect on whether we need to support zapping in the > basic MMU support. Or most specifically, we only need this zapping if we *try* to have consistent cache attributes between private and shared. In the non-coherent DMA case we can't have them be consistent because TDX doesn't support changing the private memory in this way.
