On Thu, Mar 21, 2024 at 01:17:35AM +0000, "Edgecombe, Rick P" <rick.p.edgecombe@xxxxxxxxx> wrote: > On Tue, 2024-03-19 at 17:56 -0700, Rick Edgecombe wrote: > > > Because TDX supports only WB, we > > > ignore the request for MTRR and lapic page change to not zap > > > private > > > pages on unmapping for those two cases > > > > Hmm. I need to go back and look at this again. It's not clear from > > the > > description why it is safe for the host to not zap pages if requested > > to. I see why the guest wouldn't want them to be zapped. > > Ok, I see now how this works. MTRRs and APIC zapping happen to use the > same function: kvm_zap_gfn_range(). So restricting that function from > zapping private pages has the desired affect. I think it's not ideal > that kvm_zap_gfn_range() silently skips zapping some ranges. I wonder > if we could pass something in, so it's more clear to the caller. > > But can these code paths even get reaches in TDX? It sounded like MTRRs > basically weren't supported. We can make the code paths so with the (new) assumption that guest MTRR can be disabled cleanly. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
