[PATCH v8 6/8] KVM: x86: nSVM: Save gPAT to vmcb12.g_pat on VMEXIT

Jim Mattson
2026-04-07T19:03:57Z

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>
---
arch/x86/kvm/svm/nested.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 8c9dd685b616..cf6356c775e6 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1250,6 +1250,9 @@ 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;
--
2.53.0.1213.gd9a14994de-goog