linux-kernel - [PATCH v3 17/26] KVM: nSVM: Add missing consistency check for hCR0.PG and NP

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Message-ID: <20251215192722.3654335-19-yosry.ahmed@linux.dev>
Date: Mon, 15 Dec 2025 19:27:12 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	stable@...r.kernel.org
Subject: [PATCH v3 17/26] KVM: nSVM: Add missing consistency check for hCR0.PG and NP_ENABLE

>From the APM Volume #2, 15.25.3 (24593—Rev. 3.42—March 2024):

	If VMRUN is executed with hCR0.PG cleared to zero and NP_ENABLE
	set to 1 , VMRUN terminates with #VMEXIT(VMEXIT_INVALID).

Add the consistency check by plumbing L1's CR0 to
nested_vmcb_check_controls().

Fixes: 4b16184c1cca ("KVM: SVM: Initialize Nested Nested MMU context on VMRUN")
Cc: stable@...r.kernel.org
Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 arch/x86/kvm/svm/nested.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index cac61d65efc7..5184e5ae8ccf 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -327,7 +327,8 @@ static bool nested_svm_check_bitmap_pa(struct kvm_vcpu *vcpu, u64 pa, u32 size)
 }
 
 static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
-				       struct vmcb_ctrl_area_cached *control)
+				       struct vmcb_ctrl_area_cached *control,
+				       unsigned long l1_cr0)
 {
 	if (CC(!vmcb12_is_intercept(control, INTERCEPT_VMRUN)))
 		return false;
@@ -338,6 +339,8 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 	if (nested_npt_enabled(to_svm(vcpu))) {
 		if (CC(!kvm_vcpu_is_legal_gpa(vcpu, control->nested_cr3)))
 			return false;
+		if (CC(!(l1_cr0 & X86_CR0_PG)))
+			return false;
 	}
 
 	if (CC(!nested_svm_check_bitmap_pa(vcpu, control->msrpm_base_pa,
@@ -902,7 +905,8 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb12_gpa,
 	enter_guest_mode(vcpu);
 
 	if (!nested_vmcb_check_save(vcpu, &svm->nested.save) ||
-	    !nested_vmcb_check_controls(vcpu, &svm->nested.ctl))
+	    !nested_vmcb_check_controls(vcpu, &svm->nested.ctl,
+					svm->vmcb01.ptr->save.cr0))
 		return -EINVAL;
 
 	if (nested_npt_enabled(svm))
@@ -1823,7 +1827,8 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 
 	ret = -EINVAL;
 	__nested_copy_vmcb_control_to_cache(vcpu, &ctl_cached, ctl);
-	if (!nested_vmcb_check_controls(vcpu, &ctl_cached))
+	/* 'save' contains L1 state saved from before VMRUN */
+	if (!nested_vmcb_check_controls(vcpu, &ctl_cached, save->cr0))
 		goto out_free;
 
 	/*
-- 
2.52.0.239.gd5f0c6e74e-goog