linux-kernel - [PATCH 2/2] KVM: x86: Use a switch statement in __feature

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Date:   Mon, 23 Oct 2023 17:16:36 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        "'Paolo Bonzini '" <pbonzini@...hat.com>,
        "'Sean Christopherson '" <seanjc@...gle.com>
Cc:     Jim Mattson <jmattson@...gle.com>
Subject: [PATCH 2/2] KVM: x86: Use a switch statement in __feature_translate()

The compiler will probably do better than linear search.

No functional change intended.

Signed-off-by: Jim Mattson <jmattson@...gle.com>
---
 arch/x86/kvm/reverse_cpuid.h | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 17007016d8b5..da52f5ea0351 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -116,20 +116,22 @@ static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
  */
 static __always_inline u32 __feature_translate(int x86_feature)
 {
-	if (x86_feature == X86_FEATURE_SGX1)
+	switch (x86_feature) {
+	case X86_FEATURE_SGX1:
 		return KVM_X86_FEATURE_SGX1;
-	else if (x86_feature == X86_FEATURE_SGX2)
+	case X86_FEATURE_SGX2:
 		return KVM_X86_FEATURE_SGX2;
-	else if (x86_feature == X86_FEATURE_SGX_EDECCSSA)
+	case X86_FEATURE_SGX_EDECCSSA:
 		return KVM_X86_FEATURE_SGX_EDECCSSA;
-	else if (x86_feature == X86_FEATURE_CONSTANT_TSC)
+	case X86_FEATURE_CONSTANT_TSC:
 		return KVM_X86_FEATURE_CONSTANT_TSC;
-	else if (x86_feature == X86_FEATURE_PERFMON_V2)
+	case X86_FEATURE_PERFMON_V2:
 		return KVM_X86_FEATURE_PERFMON_V2;
-	else if (x86_feature == X86_FEATURE_RRSBA_CTRL)
+	case X86_FEATURE_RRSBA_CTRL:
 		return KVM_X86_FEATURE_RRSBA_CTRL;
-
-	return x86_feature;
+	default:
+		return x86_feature;
+	}
 }
 
 static __always_inline u32 __feature_leaf(int x86_feature)
-- 
2.42.0.758.gaed0368e0e-goog