Re: [PATCH v3 8/8] KVM: x86/cpuid: Use fast return for cpuid "0xa" leaf when !enable_pmu

Sean Christopherson
2023-01-20T01:12:03Z

On Fri, Nov 11, 2022, Like Xu wrote:
> From: Like Xu <likexu@tencent.com>
>
> 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.

I doubt my motivation was performance, I'm guessing I suggested adding the explicit
!enable_pmu check because relying on kvm_pmu_cap to be zeroed isn't obvious.