linux-kernel - [PATCH 5/9] KVM: nVMX: Add consistency check for TPR

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Message-ID: <20250919005955.1366256-6-seanjc@google.com>
Date: Thu, 18 Sep 2025 17:59:51 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/9] KVM: nVMX: Add consistency check for TPR_THRESHOLD[31:4]!=0
 without VID

Add a missing consistency check on the TPR Threshold.  Per the SDM

  If the "use TPR shadow" VM-execution control is 1 and the "virtual-
  interrupt delivery" VM-execution control is 0, bits 31:4 of the TPR
  threshold VM-execution control field must be 0.

Note, nested_vmx_check_tpr_shadow_controls() bails early if "use TPR
shadow" is 0.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/nested.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 253e93ced9dc..5ac7ad207ef7 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -555,6 +555,9 @@ static int nested_vmx_check_tpr_shadow_controls(struct kvm_vcpu *vcpu,
 	if (CC(!page_address_valid(vcpu, vmcs12->virtual_apic_page_addr)))
 		return -EINVAL;
 
+	if (CC(!nested_cpu_has_vid(vmcs12) && vmcs12->tpr_threshold >> 4))
+		return -EINVAL;
+
 	return 0;
 }
 
-- 
2.51.0.470.ga7dc726c21-goog