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Peter Anvin" , Shuah Khan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Yosry Ahmed Content-Type: text/plain; charset="us-ascii" On Thu, Feb 05, 2026, Jim Mattson wrote: > Cache g_pat from vmcb12 in svm->nested.gpat to avoid TOCTTOU issues, and > add a validity check so that when nested paging is enabled for vmcb12, an > invalid g_pat causes an immediate VMEXIT with exit code VMEXIT_INVALID, as > specified in the APM, volume 2: "Nested Paging and VMRUN/VMEXIT." > > Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler") > Signed-off-by: Jim Mattson > --- > arch/x86/kvm/svm/nested.c | 4 +++- > arch/x86/kvm/svm/svm.h | 3 +++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index f72dbd10dcad..1d4ff6408b34 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -1027,9 +1027,11 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu) > > nested_copy_vmcb_control_to_cache(svm, &vmcb12->control); > nested_copy_vmcb_save_to_cache(svm, &vmcb12->save); > + svm->nested.gpat = vmcb12->save.g_pat; > > if (!nested_vmcb_check_save(vcpu) || > - !nested_vmcb_check_controls(vcpu)) { > + !nested_vmcb_check_controls(vcpu) || > + (nested_npt_enabled(svm) && !kvm_pat_valid(svm->nested.gpat))) { > vmcb12->control.exit_code = SVM_EXIT_ERR; > vmcb12->control.exit_info_1 = 0; > vmcb12->control.exit_info_2 = 0; > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 986d90f2d4ca..42a4bf83b3aa 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -208,6 +208,9 @@ struct svm_nested_state { > */ > struct vmcb_save_area_cached save; > > + /* Cached guest PAT from vmcb12.save.g_pat */ > + u64 gpat; Shouldn't this go in vmcb_save_area_cached? > + > bool initialized; > > /* > -- > 2.53.0.rc2.204.g2597b5adb4-goog >