linux-kernel - [PATCH] KVM: x86: Add a helper to dedup reporting of unhandled VM-Exits

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Message-ID: <20251030185004.3372256-1-seanjc@google.com>
Date: Thu, 30 Oct 2025 11:50:03 -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] KVM: x86: Add a helper to dedup reporting of unhandled VM-Exits

Add and use a helper, kvm_prepare_unexpected_reason_exit(), to dedup the
code that fills the exit reason and CPU when KVM encounters a VM-Exit that
KVM doesn't know how to handle.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/svm/svm.c          |  7 +------
 arch/x86/kvm/vmx/tdx.c          |  6 +-----
 arch/x86/kvm/vmx/vmx.c          |  9 +--------
 arch/x86/kvm/x86.c              | 12 ++++++++++++
 5 files changed, 16 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 48598d017d6f..4fbe4b7ce1da 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2167,6 +2167,7 @@ void __kvm_prepare_emulation_failure_exit(struct kvm_vcpu *vcpu,
 void kvm_prepare_emulation_failure_exit(struct kvm_vcpu *vcpu);
 
 void kvm_prepare_event_vectoring_exit(struct kvm_vcpu *vcpu, gpa_t gpa);
+void kvm_prepare_unexpected_reason_exit(struct kvm_vcpu *vcpu, u64 exit_reason);
 
 void kvm_enable_efer_bits(u64);
 bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f14709a511aa..83e0d4d5f4c5 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3451,13 +3451,8 @@ static bool svm_check_exit_valid(u64 exit_code)
 
 static int svm_handle_invalid_exit(struct kvm_vcpu *vcpu, u64 exit_code)
 {
-	vcpu_unimpl(vcpu, "svm: unexpected exit reason 0x%llx\n", exit_code);
 	dump_vmcb(vcpu);
-	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-	vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
-	vcpu->run->internal.ndata = 2;
-	vcpu->run->internal.data[0] = exit_code;
-	vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
+	kvm_prepare_unexpected_reason_exit(vcpu, exit_code);
 	return 0;
 }
 
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 326db9b9c567..079d9f13eddb 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2145,11 +2145,7 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 	}
 
 unhandled_exit:
-	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-	vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
-	vcpu->run->internal.ndata = 2;
-	vcpu->run->internal.data[0] = vp_enter_ret;
-	vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
+	kvm_prepare_unexpected_reason_exit(vcpu, vp_enter_ret);
 	return 0;
 }
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1021d3b65ea0..08f7957ed4c3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6642,15 +6642,8 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	return kvm_vmx_exit_handlers[exit_handler_index](vcpu);
 
 unexpected_vmexit:
-	vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",
-		    exit_reason.full);
 	dump_vmcs(vcpu);
-	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-	vcpu->run->internal.suberror =
-			KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
-	vcpu->run->internal.ndata = 2;
-	vcpu->run->internal.data[0] = exit_reason.full;
-	vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
+	kvm_prepare_unexpected_reason_exit(vcpu, exit_reason.full);
 	return 0;
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b4b5d2d09634..c826cd05228a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9110,6 +9110,18 @@ void kvm_prepare_event_vectoring_exit(struct kvm_vcpu *vcpu, gpa_t gpa)
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_prepare_event_vectoring_exit);
 
+void kvm_prepare_unexpected_reason_exit(struct kvm_vcpu *vcpu, u64 exit_reason)
+{
+	vcpu_unimpl(vcpu, "unexpected exit reason 0x%llx\n", exit_reason);
+
+	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+	vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
+	vcpu->run->internal.ndata = 2;
+	vcpu->run->internal.data[0] = exit_reason;
+	vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_prepare_unexpected_reason_exit);
+
 static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
 {
 	struct kvm *kvm = vcpu->kvm;

base-commit: 4cc167c50eb19d44ac7e204938724e685e3d8057
-- 
2.51.1.930.gacf6e81ea2-goog