linux-kernel - [PATCH 4/9] KVM: x86: Avoid double CPUID lookup when updating MWAIT at runtime

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Message-ID: <20231110235528.1561679-5-seanjc@google.com>
Date:   Fri, 10 Nov 2023 15:55:23 -0800
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,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 4/9] KVM: x86: Avoid double CPUID lookup when updating MWAIT
 at runtime

Move the handling of X86_FEATURE_MWAIT during CPUID runtime updates to
utilize the lookup done for other CPUID.0x1 features.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/cpuid.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 5cf3d697ecb3..6777780be6ae 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -276,6 +276,11 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
 
 		cpuid_entry_change(best, X86_FEATURE_APIC,
 			   vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
+
+		if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT))
+			cpuid_entry_change(best, X86_FEATURE_MWAIT,
+					   vcpu->arch.ia32_misc_enable_msr &
+					   MSR_IA32_MISC_ENABLE_MWAIT);
 	}
 
 	best = cpuid_entry2_find(entries, nent, 7, 0);
@@ -296,14 +301,6 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
 	if (kvm_hlt_in_guest(vcpu->kvm) && best &&
 		(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
 		best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
-
-	if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
-		best = cpuid_entry2_find(entries, nent, 0x1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
-		if (best)
-			cpuid_entry_change(best, X86_FEATURE_MWAIT,
-					   vcpu->arch.ia32_misc_enable_msr &
-					   MSR_IA32_MISC_ENABLE_MWAIT);
-	}
 }
 
 void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
-- 
2.42.0.869.gea05f2083d-goog