KVM: x86: nSVM: Save gPAT to vmcb12.g_pat on VMEXIT

According to the APM volume 3 pseudo-code for "VMRUN," when nested paging
is enabled in the vmcb, the guest PAT register (gPAT) is saved to the vmcb
on emulated VMEXIT.

When KVM_X86_QUIRK_NESTED_SVM_SHARED_PAT is disabled and the vCPU is in
guest mode with nested NPT enabled, save the vmcb02 g_pat field to the
vmcb12 g_pat field on emulated VMEXIT.

Fixes: 15038e147247 ("KVM: SVM: obey guest PAT")
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260407190343.325299-7-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index e70839d4531cafffb272d4684ab9b25d00bfe71b..1db821181f43f3ea036e81932234716ad81f2578 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1258,6 +1258,9 @@ static int nested_svm_vmexit_update_vmcb12(struct kvm_vcpu *vcpu)
        vmcb12->save.dr6    = svm->vcpu.arch.dr6;
        vmcb12->save.cpl    = vmcb02->save.cpl;
 
+       if (l2_has_separate_pat(vcpu))
+               vmcb12->save.g_pat = vmcb02->save.g_pat;
+
        if (guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK)) {
                vmcb12->save.s_cet      = vmcb02->save.s_cet;
                vmcb12->save.isst_addr  = vmcb02->save.isst_addr;