[PATCH v4 07/12] KVM: x86/cpuid: Use fast return for cpuid "0xa" leaf when !enable_pmu

[Like Xu]

From: Like Xu <likexu@xxxxxxxxxxx>

Add an explicit !enable_pmu check as relying on kvm_pmu_cap to be
zeroed isn't obvious. Although when !enable_pmu, KVM will have
zero-padded kvm_pmu_cap to do subsequent cpuid leaf assignments,
one extra branch instruction saves a few subsequent zero-assignment
instructions, speeding things up a bit.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
 arch/x86/kvm/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 2a9f1e200dbc..b0bb5f9f5307 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -944,7 +944,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		union cpuid10_eax eax;
 		union cpuid10_edx edx;
 
-		if (!static_cpu_has(X86_FEATURE_ARCH_PERFMON)) {
+		if (!enable_pmu || !static_cpu_has(X86_FEATURE_ARCH_PERFMON)) {
 			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
 			break;
 		}
-- 
2.39.1