On Fri, Feb 6, 2026 at 11:18 AM Sean Christopherson <[email protected]> wrote: > > On Thu, Feb 05, 2026, Jim Mattson wrote: > > When nested NPT is enabled and KVM_SET_NESTED_STATE is used to restore an > > old checkpoint (without a valid gPAT), the current IA32_PAT value must be > > used as L2's gPAT. > > > > The current IA32_PAT value may be restored by KVM_SET_MSRS after > > KVM_SET_NESTED_STATE. Furthermore, there may be a KVM_GET_NESTED_STATE > > before the first KVM_RUN. > > > > Introduce a new boolean, svm->nested.legacy_gpat_semantics. When set, hPAT > > updates are also applied to gPAT, preserving the old behavior where L2 > > shared L1's PAT. svm_vcpu_pre_run() clears this boolean at the first > > KVM_RUN. > > State this last point as a command and explain why. E.g. I think this is why? > > Clear legacy_gpat_semantics on KVM_RUN so that the legacy semantics are > scoped to a single restore (inasmuch as possible). E.g. to support > restoring a snapshot from an old KVM, and then later restoring a snapshot > from a new KVM.
Actually, it's just because I'd like to return to normal behavior once the non-atomic restore operation is complete. I'll add that note.
