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SubjectRe: [PATCH v3 2/3] KVM: vPMU: Fill get_msr MSR_CORE_PERF_GLOBAL_OVF_CTRL w/ 0
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On 19/10/21 10:12, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> SDM section 18.2.3 mentioned that:
>
> "IA32_PERF_GLOBAL_OVF_CTL MSR allows software to clear overflow indicator(s) of
> any general-purpose or fixed-function counters via a single WRMSR."
>
> It is R/W mentioned by SDM, we read this msr on bare-metal during perf testing,
> the value is always 0 for ICX/SKX boxes on hands. Let's fill get_msr
> MSR_CORE_PERF_GLOBAL_OVF_CTRL w/ 0 as hardware behavior and drop
> global_ovf_ctrl variable.
>
> Tested-by: Like Xu <likexu@tencent.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> Btw, xen also fills get_msr MSR_CORE_PERF_GLOBAL_OVF_CTRL w/ 0.
> v1 -> v2:
> * drop 'u64 global_ovf_ctrl' directly
>
> arch/x86/include/asm/kvm_host.h | 1 -
> arch/x86/kvm/vmx/pmu_intel.c | 6 ++----
> 2 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index f8f48a7ec577..7aaac918e992 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -499,7 +499,6 @@ struct kvm_pmu {
> u64 fixed_ctr_ctrl;
> u64 global_ctrl;
> u64 global_status;
> - u64 global_ovf_ctrl;
> u64 counter_bitmask[2];
> u64 global_ctrl_mask;
> u64 global_ovf_ctrl_mask;
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index 10cc4f65c4ef..b8e0d21b7c8a 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -365,7 +365,7 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> msr_info->data = pmu->global_ctrl;
> return 0;
> case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
> - msr_info->data = pmu->global_ovf_ctrl;
> + msr_info->data = 0;
> return 0;
> default:
> if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
> @@ -423,7 +423,6 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> if (!(data & pmu->global_ovf_ctrl_mask)) {
> if (!msr_info->host_initiated)
> pmu->global_status &= ~data;
> - pmu->global_ovf_ctrl = data;
> return 0;
> }
> break;
> @@ -588,8 +587,7 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
> pmc->counter = 0;
> }
>
> - pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status =
> - pmu->global_ovf_ctrl = 0;
> + pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status = 0;
>
> intel_pmu_release_guest_lbr_event(vcpu);
> }
>

Queued, thanks.

Paolo

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