From: Sean Christopherson <seanjc@google.com>
To: Like Xu <like.xu.linux@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 8/8] KVM: x86/cpuid: Use fast return for cpuid "0xa" leaf when !enable_pmu
Date: Fri, 20 Jan 2023 01:11:54 +0000 [thread overview]
Message-ID: <Y8nqWl+kOvc8WPdK@google.com> (raw)
In-Reply-To: <20221111102645.82001-9-likexu@tencent.com>
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.
next prev parent reply other threads:[~2023-01-20 1:12 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-11 10:26 [PATCH v3 0/8] KVM: x86: Add AMD Guest PerfMonV2 PMU support Like Xu
2022-11-11 10:26 ` [PATCH v3 1/8] KVM: x86/pmu: Rename pmc_is_enabled() to pmc_is_globally_enabled() Like Xu
2023-01-27 2:03 ` Sean Christopherson
2023-02-02 11:46 ` Like Xu
2022-11-11 10:26 ` [PATCH v3 2/8] KVM: VMX: Refactor intel_pmu_set_msr() to align with other set_msr() helpers Like Xu
2023-01-27 2:09 ` Sean Christopherson
2022-11-11 10:26 ` [PATCH v3 3/8] KVM: x86/pmu: Rewrite reprogram_counters() to improve performance Like Xu
2023-01-20 1:09 ` Sean Christopherson
2023-01-24 20:16 ` Sean Christopherson
2022-11-11 10:26 ` [PATCH v3 4/8] KVM: x86/pmu: Make part of the Intel v2 PMU MSRs handling x86 generic Like Xu
2022-11-11 10:26 ` [PATCH v3 5/8] KVM: x86/cpuid: Add X86_FEATURE_AMD_PMU_V2 as a KVM-only leaf entry Like Xu
2023-01-24 19:47 ` Sean Christopherson
2023-02-06 11:47 ` Like Xu
2023-02-10 1:32 ` Sean Christopherson
2022-11-11 10:26 ` [PATCH v3 6/8] KVM: x86/svm/pmu: Add AMD PerfMonV2 support Like Xu
2023-01-25 0:10 ` Sean Christopherson
2023-02-06 7:53 ` Like Xu
2023-02-06 22:22 ` Sean Christopherson
2022-11-11 10:26 ` [PATCH v3 7/8] KVM: x86/cpuid: Add AMD CPUID ExtPerfMonAndDbg leaf 0x80000022 Like Xu
2023-01-25 0:16 ` Sean Christopherson
2022-11-11 10:26 ` [PATCH v3 8/8] KVM: x86/cpuid: Use fast return for cpuid "0xa" leaf when !enable_pmu Like Xu
2023-01-20 1:11 ` Sean Christopherson [this message]
2022-12-06 8:32 ` [PATCH v3 0/8] KVM: x86: Add AMD Guest PerfMonV2 PMU support Like Xu
2023-01-20 1:13 ` Sean Christopherson
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