linux-kernel - [PATCH v2 3/8] KVM: x86: nSVM: Add validity check for vmcb12 g

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Message-ID: <20260115232154.3021475-4-jmattson@google.com>
Date: Thu, 15 Jan 2026 15:21:42 -0800
From: Jim Mattson <jmattson@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Shuah Khan <shuah@...nel.org>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc: Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v2 3/8] KVM: x86: nSVM: Add validity check for vmcb12 g_pat

Add a validity check for g_pat, 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."

Update the signature of __nested_vmcb_check_save() to include a pointer to
a struct vmcb_ctrl_area_cached, since the g_pat validity check depend on
the nested paging control bit.

Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler")
Signed-off-by: Jim Mattson <jmattson@...gle.com>
---
 arch/x86/kvm/svm/nested.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 07a57a43fc3b..e65291434be9 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -369,7 +369,8 @@ static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 
 /* Common checks that apply to both L1 and L2 state.  */
 static bool __nested_vmcb_check_save(struct kvm_vcpu *vcpu,
-				     struct vmcb_save_area_cached *save)
+				     struct vmcb_save_area_cached *save,
+				     struct vmcb_ctrl_area_cached *control)
 {
 	if (CC(!(save->efer & EFER_SVME)))
 		return false;
@@ -400,6 +401,10 @@ static bool __nested_vmcb_check_save(struct kvm_vcpu *vcpu,
 	if (CC(!kvm_valid_efer(vcpu, save->efer)))
 		return false;
 
+	if (CC((control->nested_ctl & SVM_NESTED_CTL_NP_ENABLE) &&
+	       npt_enabled && !kvm_pat_valid(save->g_pat)))
+		return false;
+
 	return true;
 }
 
@@ -407,8 +412,9 @@ static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct vmcb_save_area_cached *save = &svm->nested.save;
+	struct vmcb_ctrl_area_cached *ctl = &svm->nested.ctl;
 
-	return __nested_vmcb_check_save(vcpu, save);
+	return __nested_vmcb_check_save(vcpu, save, ctl);
 }
 
 static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu)
@@ -1892,7 +1898,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	if (!(save->cr0 & X86_CR0_PG) ||
 	    !(save->cr0 & X86_CR0_PE) ||
 	    (save->rflags & X86_EFLAGS_VM) ||
-	    !__nested_vmcb_check_save(vcpu, &save_cached))
+	    !__nested_vmcb_check_save(vcpu, &save_cached, &ctl_cached))
 		goto out_free;
 
 
-- 
2.52.0.457.g6b5491de43-goog