On Mon, Jan 12, 2026, Jim Mattson wrote: > KVM doesn't implement a separate G_PAT register to hold the guest's > PAT in guest mode with nested NPT enabled. Consequently, L1's IA32_PAT > MSR must be restored on emulated #VMEXIT from L2 to L1. > > Note: if L2 uses shadow paging, L1 and L2 share the same IA32_PAT MSR. > > Signed-off-by: Jim Mattson <[email protected]> > --- > arch/x86/kvm/svm/nested.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index c751be470364..9aec836ac04c 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -1292,6 +1292,16 @@ int nested_svm_vmexit(struct vcpu_svm *svm) > kvm_rsp_write(vcpu, vmcb01->save.rsp); > kvm_rip_write(vcpu, vmcb01->save.rip); > > + /* > + * KVM doesn't implement a separate guest PAT > + * register. Instead, the guest PAT lives in vcpu->arch.pat > + * while in guest mode with nested NPT enabled. Hence, the > + * IA32_PAT MSR has to be restored from the vmcb01 g_pat at > + * #VMEXIT.
Wrap closer to 80 chars. > + */ > + if (nested_npt_enabled(svm)) > + vcpu->arch.pat = vmcb01->save.g_pat; > + > svm->vcpu.arch.dr7 = DR7_FIXED_1; > kvm_update_dr7(&svm->vcpu); > > -- > 2.52.0.457.g6b5491de43-goog >
