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Date: Tue, 20 Apr 2021 16:41:36 +0800
From: "Xu, Like" <like.xu@...el.com>
To: Liuxiangdong <liuxiangdong5@...wei.com>
Cc: andi@...stfloor.org, kan.liang@...ux.intel.com,
wei.w.wang@...el.com, eranian@...gle.com,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
x86@...nel.org, linux-kernel@...r.kernel.org,
"Fangyi (Eric)" <eric.fangyi@...wei.com>,
Xiexiangyou <xiexiangyou@...wei.com>,
Peter Zijlstra <peterz@...radead.org>,
Like Xu <like.xu@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH v5 10/16] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE
when PEBS is enabled
On 2021/4/20 16:30, Liuxiangdong wrote:
>
>
> On 2021/4/15 11:20, Like Xu wrote:
>> The bit 12 represents "Processor Event Based Sampling Unavailable (RO)" :
>> 1 = PEBS is not supported.
>> 0 = PEBS is supported.
>>
>> A write to this PEBS_UNAVL available bit will bring #GP(0) when guest PEBS
>> is enabled. Some PEBS drivers in guest may care about this bit.
>>
>> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
>> ---
>> arch/x86/kvm/vmx/pmu_intel.c | 2 ++
>> arch/x86/kvm/x86.c | 4 ++++
>> 2 files changed, 6 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
>> index 58f32a55cc2e..c846d3eef7a7 100644
>> --- a/arch/x86/kvm/vmx/pmu_intel.c
>> +++ b/arch/x86/kvm/vmx/pmu_intel.c
>> @@ -588,6 +588,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>> bitmap_set(pmu->all_valid_pmc_idx, INTEL_PMC_IDX_FIXED_VLBR, 1);
>> if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) {
>> + vcpu->arch.ia32_misc_enable_msr &=
>> ~MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
>> if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_BASELINE) {
>> pmu->pebs_enable_mask = ~pmu->global_ctrl;
>> pmu->reserved_bits &= ~ICL_EVENTSEL_ADAPTIVE;
>> @@ -597,6 +598,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>> }
>> pmu->pebs_data_cfg_mask = ~0xff00000full;
>> } else {
>> + vcpu->arch.ia32_misc_enable_msr |=
>> MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
>> pmu->pebs_enable_mask =
>> ~((1ull << pmu->nr_arch_gp_counters) - 1);
>> }
>
> I guess what we want is
>
> if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) {
> vcpu->arch.ia32_misc_enable_msr &=
> ~MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
> if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_BASELINE) {
> pmu->pebs_enable_mask = ~pmu->global_ctrl;
> pmu->reserved_bits &= ~ICL_EVENTSEL_ADAPTIVE;
> for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
> pmu->fixed_ctr_ctrl_mask &=
> ~(1ULL << (INTEL_PMC_IDX_FIXED + i
> * 4));
> }
> pmu->pebs_data_cfg_mask = ~0xff00000full;
> } else {
> pmu->pebs_enable_mask =
> ~((1ull << pmu->nr_arch_gp_counters) - 1);
> }
> } else {
> vcpu->arch.ia32_misc_enable_msr |=
> MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
> vcpu->arch.perf_capabilities &= ~PERF_CAP_PEBS_MASK;
> }
>
>
> But here is
>
> if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) {
> vcpu->arch.ia32_misc_enable_msr &=
> ~MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
> if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_BASELINE) {
> pmu->pebs_enable_mask = ~pmu->global_ctrl;
> pmu->reserved_bits &= ~ICL_EVENTSEL_ADAPTIVE;
> for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
> pmu->fixed_ctr_ctrl_mask &=
> ~(1ULL << (INTEL_PMC_IDX_FIXED + i
> * 4));
> }
> pmu->pebs_data_cfg_mask = ~0xff00000full;
> } else {
> vcpu->arch.ia32_misc_enable_msr |=
> MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
You got me. The v5 is wrong here but v4 is right.
Please let me know if you have more comments on this version.
> pmu->pebs_enable_mask =
> ~((1ull << pmu->nr_arch_gp_counters) - 1);
> }
> } else {
> vcpu->arch.perf_capabilities &= ~PERF_CAP_PEBS_MASK;
> }
>
>
> Wrong else branch?
>
>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 1a64e816e06d..ed38f1dada63 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -3126,6 +3126,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu,
>> struct msr_data *msr_info)
>> break;
>> case MSR_IA32_MISC_ENABLE:
>> data &= ~MSR_IA32_MISC_ENABLE_EMON;
>> + if (!msr_info->host_initiated &&
>> + (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) &&
>> + (data & MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL))
>> + return 1;
>> if (!kvm_check_has_quirk(vcpu->kvm,
>> KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT) &&
>> ((vcpu->arch.ia32_misc_enable_msr ^ data) &
>> MSR_IA32_MISC_ENABLE_MWAIT)) {
>> if (!guest_cpuid_has(vcpu, X86_FEATURE_XMM3))
>
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