[PATCH 5/9] KVM: SVM: Check for an unexpected VM-Exit after RETPOLINE "fast" handling

Sean Christopherson posted 9 patches 2 months, 3 weeks ago
[PATCH 5/9] KVM: SVM: Check for an unexpected VM-Exit after RETPOLINE "fast" handling
Posted by Sean Christopherson 2 months, 3 weeks ago
Check for an unexpected/unhandled VM-Exit after the manual RETPOLINE=y
handling.  The entire point of the RETPOLINE checks is to optimize for
common VM-Exits, i.e. checking for the rare case of an unsupported
VM-Exit is counter-productive.  This also aligns SVM and VMX exit handling.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 638a67ef0c37..202a4d8088a2 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3435,12 +3435,6 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
 
 int svm_invoke_exit_handler(struct kvm_vcpu *vcpu, u64 exit_code)
 {
-	if (exit_code >= ARRAY_SIZE(svm_exit_handlers))
-		goto unexpected_vmexit;
-
-	if (!svm_exit_handlers[exit_code])
-		goto unexpected_vmexit;
-
 #ifdef CONFIG_MITIGATION_RETPOLINE
 	if (exit_code == SVM_EXIT_MSR)
 		return msr_interception(vcpu);
@@ -3457,6 +3451,12 @@ int svm_invoke_exit_handler(struct kvm_vcpu *vcpu, u64 exit_code)
 		return sev_handle_vmgexit(vcpu);
 #endif
 #endif
+	if (exit_code >= ARRAY_SIZE(svm_exit_handlers))
+		goto unexpected_vmexit;
+
+	if (!svm_exit_handlers[exit_code])
+		goto unexpected_vmexit;
+
 	return svm_exit_handlers[exit_code](vcpu);
 
 unexpected_vmexit:
-- 
2.52.0.rc1.455.g30608eb744-goog
Re: [PATCH 5/9] KVM: SVM: Check for an unexpected VM-Exit after RETPOLINE "fast" handling
Posted by Yosry Ahmed 2 months, 3 weeks ago
On Thu, Nov 13, 2025 at 02:56:17PM -0800, Sean Christopherson wrote:
> Check for an unexpected/unhandled VM-Exit after the manual RETPOLINE=y
> handling.  The entire point of the RETPOLINE checks is to optimize for
> common VM-Exits, i.e. checking for the rare case of an unsupported
> VM-Exit is counter-productive.  This also aligns SVM and VMX exit handling.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>

> ---
>  arch/x86/kvm/svm/svm.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 638a67ef0c37..202a4d8088a2 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3435,12 +3435,6 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
>  
>  int svm_invoke_exit_handler(struct kvm_vcpu *vcpu, u64 exit_code)
>  {
> -	if (exit_code >= ARRAY_SIZE(svm_exit_handlers))
> -		goto unexpected_vmexit;
> -
> -	if (!svm_exit_handlers[exit_code])
> -		goto unexpected_vmexit;
> -
>  #ifdef CONFIG_MITIGATION_RETPOLINE
>  	if (exit_code == SVM_EXIT_MSR)
>  		return msr_interception(vcpu);
> @@ -3457,6 +3451,12 @@ int svm_invoke_exit_handler(struct kvm_vcpu *vcpu, u64 exit_code)
>  		return sev_handle_vmgexit(vcpu);
>  #endif
>  #endif
> +	if (exit_code >= ARRAY_SIZE(svm_exit_handlers))
> +		goto unexpected_vmexit;
> +
> +	if (!svm_exit_handlers[exit_code])
> +		goto unexpected_vmexit;
> +
>  	return svm_exit_handlers[exit_code](vcpu);
>  
>  unexpected_vmexit:
> -- 
> 2.52.0.rc1.455.g30608eb744-goog
>