linux-kernel - [PATCH v2 8/8] KVM: SVM: Assert that Hyper-V's HV_SVM_EXITCODE_ENL == SVM_EXIT

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Message-ID: <20251230211347.4099600-9-seanjc@google.com>
Date: Tue, 30 Dec 2025 13:13:47 -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>, Long Li <longli@...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 v2 8/8] KVM: SVM: Assert that Hyper-V's HV_SVM_EXITCODE_ENL == SVM_EXIT_SW

Add a build-time assertiont that Hyper-V's "enlightened" exit code is that,
same as the AMD-defined "Reserved for Host" exit code, mostly to help
readers connect the dots and understand why synthesizing a software-defined
exit code is safe/ok.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/hyperv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/svm/hyperv.c b/arch/x86/kvm/svm/hyperv.c
index 3ec580d687f5..4f24dcb45116 100644
--- a/arch/x86/kvm/svm/hyperv.c
+++ b/arch/x86/kvm/svm/hyperv.c
@@ -10,6 +10,12 @@ void svm_hv_inject_synthetic_vmexit_post_tlb_flush(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
+	/*
+	 * The exit code used by Hyper-V for software-defined exits is reserved
+	 * by AMD specifically for such use cases.
+	 */
+	BUILD_BUG_ON(HV_SVM_EXITCODE_ENL != SVM_EXIT_SW);
+
 	svm->vmcb->control.exit_code = HV_SVM_EXITCODE_ENL;
 	svm->vmcb->control.exit_info_1 = HV_SVM_ENL_EXITCODE_TRAP_AFTER_FLUSH;
 	svm->vmcb->control.exit_info_2 = 0;
-- 
2.52.0.351.gbe84eed79e-goog