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Date: Fri, 29 Apr 2022 13:45:02 +0800
From: "Yang, Weijiang" <weijiang.yang@...el.com>
To: "Liang, Kan" <kan.liang@...ux.intel.com>,
"pbonzini@...hat.com" <pbonzini@...hat.com>,
"jmattson@...gle.com" <jmattson@...gle.com>,
"seanjc@...gle.com" <seanjc@...gle.com>,
"like.xu.linux@...il.com" <like.xu.linux@...il.com>,
"vkuznets@...hat.com" <vkuznets@...hat.com>,
"Wang, Wei W" <wei.w.wang@...el.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 08/16] KVM: x86/pmu: Refactor code to support guest
Arch LBR
On 4/28/2022 10:18 PM, Liang, Kan wrote:
>
> On 4/22/2022 3:55 AM, Yang Weijiang wrote:
>> Take account of Arch LBR when do sanity checks before program
>> vPMU for guest. Pass through Arch LBR recording MSRs to guest
>> to gain better performance. Note, Arch LBR and Legacy LBR support
>> are mutually exclusive, i.e., they're not both available on one
>> platform.
>>
>> Co-developed-by: Like Xu <like.xu@...ux.intel.com>
>> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
>> ---
>> arch/x86/kvm/vmx/pmu_intel.c | 37 +++++++++++++++++++++++++++++-------
>> arch/x86/kvm/vmx/vmx.c | 3 +++
>> 2 files changed, 33 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
>> index 7dc8a5783df7..cb28888e9f4f 100644
>> --- a/arch/x86/kvm/vmx/pmu_intel.c
>> +++ b/arch/x86/kvm/vmx/pmu_intel.c
>> @@ -170,12 +170,16 @@ static inline struct kvm_pmc *get_fw_gp_pmc(struct kvm_pmu *pmu, u32 msr)
>>
>> bool intel_pmu_lbr_is_compatible(struct kvm_vcpu *vcpu)
>> {
>> + if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
>> + return guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR);
>> +
>> /*
>> * As a first step, a guest could only enable LBR feature if its
>> * cpu model is the same as the host because the LBR registers
>> * would be pass-through to the guest and they're model specific.
>> */
>> - return boot_cpu_data.x86_model == guest_cpuid_model(vcpu);
>> + return !boot_cpu_has(X86_FEATURE_ARCH_LBR) &&
>> + boot_cpu_data.x86_model == guest_cpuid_model(vcpu);
>> }
>>
>> bool intel_pmu_lbr_is_enabled(struct kvm_vcpu *vcpu)
>> @@ -193,12 +197,19 @@ static bool intel_pmu_is_valid_lbr_msr(struct kvm_vcpu *vcpu, u32 index)
> I think we should move MSR_ARCH_LBR_DEPTH and MSR_ARCH_LBR_CTL to this
> function as well, since they are LBR related MSRs.
Makes sense, will change it in next version.
>
>> if (!intel_pmu_lbr_is_enabled(vcpu))
>> return ret;
>>
>> - ret = (index == MSR_LBR_SELECT) || (index == MSR_LBR_TOS) ||
>> - (index >= records->from && index < records->from + records->nr) ||
>> - (index >= records->to && index < records->to + records->nr);
>> + if (!guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
>> + ret = (index == MSR_LBR_SELECT) || (index == MSR_LBR_TOS);
>> +
>> + if (!ret) {
>> + ret = (index >= records->from &&
>> + index < records->from + records->nr) ||
>> + (index >= records->to &&
>> + index < records->to + records->nr);
>> + }
>>
>> if (!ret && records->info)
>> - ret = (index >= records->info && index < records->info + records->nr);
>> + ret = (index >= records->info &&
>> + index < records->info + records->nr);
> Please use "{}" since you split it to two lines.
OK.
>
> Thanks,
> Kan
>>
>> return ret;
>> }
>> @@ -747,6 +758,9 @@ static void vmx_update_intercept_for_lbr_msrs(struct kvm_vcpu *vcpu, bool set)
>> vmx_set_intercept_for_msr(vcpu, lbr->info + i, MSR_TYPE_RW, set);
>> }
>>
>> + if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
>> + return;
>> +
>> vmx_set_intercept_for_msr(vcpu, MSR_LBR_SELECT, MSR_TYPE_RW, set);
>> vmx_set_intercept_for_msr(vcpu, MSR_LBR_TOS, MSR_TYPE_RW, set);
>> }
>> @@ -787,10 +801,13 @@ void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
>> {
>> struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
>> struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
>> + bool lbr_enable = guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR) ?
>> + (vmcs_read64(GUEST_IA32_LBR_CTL) & ARCH_LBR_CTL_LBREN) :
>> + (vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR);
>>
>> if (!lbr_desc->event) {
>> vmx_disable_lbr_msrs_passthrough(vcpu);
>> - if (vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR)
>> + if (lbr_enable)
>> goto warn;
>> if (test_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use))
>> goto warn;
>> @@ -807,13 +824,19 @@ void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
>> return;
>>
>> warn:
>> + if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
>> + wrmsrl(MSR_ARCH_LBR_DEPTH, lbr_desc->records.nr);
>> pr_warn_ratelimited("kvm: vcpu-%d: fail to passthrough LBR.\n",
>> vcpu->vcpu_id);
>> }
>>
>> static void intel_pmu_cleanup(struct kvm_vcpu *vcpu)
>> {
>> - if (!(vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR))
>> + bool lbr_enable = guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR) ?
>> + (vmcs_read64(GUEST_IA32_LBR_CTL) & ARCH_LBR_CTL_LBREN) :
>> + (vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR);
>> +
>> + if (!lbr_enable)
>> intel_pmu_release_guest_lbr_event(vcpu);
>> }
>>
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 73961fcfb62d..a1816c6597f5 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -573,6 +573,9 @@ static bool is_valid_passthrough_msr(u32 msr)
>> case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 31:
>> case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 8:
>> case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 8:
>> + case MSR_ARCH_LBR_FROM_0 ... MSR_ARCH_LBR_FROM_0 + 31:
>> + case MSR_ARCH_LBR_TO_0 ... MSR_ARCH_LBR_TO_0 + 31:
>> + case MSR_ARCH_LBR_INFO_0 ... MSR_ARCH_LBR_INFO_0 + 31:
>> /* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
>> return true;
>> }
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