linux-kernel - [PATCH 1/9] KVM: nSVM: Clear exit_code_hi in VMCB when synthesizing nested VM-Exits

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Message-ID: <20251113225621.1688428-2-seanjc@google.com>
Date: Thu, 13 Nov 2025 14:56:13 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
	Dexuan Cui <decui@...rosoft.com>
Cc: kvm@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH 1/9] KVM: nSVM: Clear exit_code_hi in VMCB when synthesizing
 nested VM-Exits

Explicitly clear exit_code_hi in the VMCB when synthesizing "normal"
nested VM-Exits, as the full exit code is a 64-bit value (spoiler alert),
and all exit codes for non-failing VMRUN use only bits 31:0.

Cc: Jim Mattson <jmattson@...gle.com>
Cc: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 2 ++
 arch/x86/kvm/svm/svm.h | 7 ++++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index fc42bcdbb520..7ea034ee6b6c 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2433,6 +2433,7 @@ static bool check_selective_cr0_intercepted(struct kvm_vcpu *vcpu,
 
 	if (cr0 ^ val) {
 		svm->vmcb->control.exit_code = SVM_EXIT_CR0_SEL_WRITE;
+		svm->vmcb->control.exit_code_hi = 0;
 		ret = (nested_svm_exit_handled(svm) == NESTED_EXIT_DONE);
 	}
 
@@ -4608,6 +4609,7 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
 	if (static_cpu_has(X86_FEATURE_NRIPS))
 		vmcb->control.next_rip  = info->next_rip;
 	vmcb->control.exit_code = icpt_info.exit_code;
+	vmcb->control.exit_code_hi = 0;
 	vmexit = nested_svm_exit_handled(svm);
 
 	ret = (vmexit == NESTED_EXIT_DONE) ? X86EMUL_INTERCEPTED
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index c2acaa49ee1c..253a8dca412c 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -763,9 +763,10 @@ int nested_svm_vmexit(struct vcpu_svm *svm);
 
 static inline int nested_svm_simple_vmexit(struct vcpu_svm *svm, u32 exit_code)
 {
-	svm->vmcb->control.exit_code   = exit_code;
-	svm->vmcb->control.exit_info_1 = 0;
-	svm->vmcb->control.exit_info_2 = 0;
+	svm->vmcb->control.exit_code	= exit_code;
+	svm->vmcb->control.exit_code_hi	= 0;
+	svm->vmcb->control.exit_info_1	= 0;
+	svm->vmcb->control.exit_info_2	= 0;
 	return nested_svm_vmexit(svm);
 }
 
-- 
2.52.0.rc1.455.g30608eb744-goog