linux-kernel - [RFC PATCH 5/6] KVM: x86: nSVM: Add validity check for the VMCB12 g

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Message-ID: <20251107201151.3303170-6-jmattson@google.com>
Date: Fri,  7 Nov 2025 12:11:28 -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>, Alexander Graf <agraf@...e.de>, Joerg Roedel <joro@...tes.org>, 
	Avi Kivity <avi@...hat.com>, 
	"Radim Krčmář" <rkrcmar@...hat.com>, David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Cc: Jim Mattson <jmattson@...gle.com>
Subject: [RFC PATCH 5/6] KVM: x86: nSVM: Add validity check for the VMCB12 g_pat

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.

Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler")
Signed-off-by: Jim Mattson <jmattson@...gle.com>
---
 arch/x86/kvm/svm/nested.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 6e48572e2bd7..43429399993c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -336,6 +336,10 @@ static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 	if (CC((control->nested_ctl & SVM_NESTED_CTL_NP_ENABLE) && !npt_enabled))
 		return false;
 
+	if (CC((control->nested_ctl & SVM_NESTED_CTL_NP_ENABLE) &&
+	       npt_enabled && !kvm_pat_valid(control->g_pat)))
+		return false;
+
 	if (CC(!nested_svm_check_bitmap_pa(vcpu, control->msrpm_base_pa,
 					   MSRPM_SIZE)))
 		return false;
-- 
2.51.2.1041.gc1ab5b90ca-goog