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Date: Fri, 29 Apr 2022 11:20:37 +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 07/16] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_CTL for
guest Arch LBR
On 4/28/2022 10:16 PM, Liang, Kan wrote:
>
> On 4/22/2022 3:55 AM, Yang Weijiang wrote:
>> From: Like Xu <like.xu@...ux.intel.com>
>>
>> Arch LBR is enabled by setting MSR_ARCH_LBR_CTL.LBREn to 1. A new guest
>> state field named "Guest IA32_LBR_CTL" is added to enhance guest LBR usage.
>> When guest Arch LBR is enabled, a guest LBR event will be created like the
>> model-specific LBR does. Clear guest LBR enable bit on host PMI handling so
>> guest can see expected config.
>>
>> On processors that support Arch LBR, MSR_IA32_DEBUGCTLMSR[bit 0] has no
>> meaning. It can be written to 0 or 1, but reads will always return 0.
>> Like IA32_DEBUGCTL, IA32_ARCH_LBR_CTL msr is also preserved on INIT.
>>
>> Regardless of the Arch LBR or legacy LBR, when the LBR_EN bit 0 of the
>> corresponding control MSR is set to 1, LBR recording will be enabled.
>>
>> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
>> Co-developed-by: Yang Weijiang <weijiang.yang@...el.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
>> ---
>> arch/x86/events/intel/lbr.c | 2 --
>> arch/x86/include/asm/msr-index.h | 1 +
>> arch/x86/include/asm/vmx.h | 2 ++
>> arch/x86/kvm/vmx/pmu_intel.c | 58 +++++++++++++++++++++++++++++---
>> arch/x86/kvm/vmx/vmx.c | 12 +++++++
>> 5 files changed, 68 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
>> index 4529ce448b2e..4fe6c3b50fc3 100644
>> --- a/arch/x86/events/intel/lbr.c
>> +++ b/arch/x86/events/intel/lbr.c
>> @@ -160,8 +160,6 @@ enum {
>> ARCH_LBR_RETURN |\
>> ARCH_LBR_OTHER_BRANCH)
>>
>> -#define ARCH_LBR_CTL_MASK 0x7f000e
>> -
>> static void intel_pmu_lbr_filter(struct cpu_hw_events *cpuc);
>>
>> static __always_inline bool is_lbr_call_stack_bit_set(u64 config)
>> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
>> index 0eb90d21049e..60e0ab108dc0 100644
>> --- a/arch/x86/include/asm/msr-index.h
>> +++ b/arch/x86/include/asm/msr-index.h
>> @@ -169,6 +169,7 @@
>> #define LBR_INFO_BR_TYPE (0xfull << LBR_INFO_BR_TYPE_OFFSET)
>>
>> #define MSR_ARCH_LBR_CTL 0x000014ce
>> +#define ARCH_LBR_CTL_MASK 0x7f000e
>> #define ARCH_LBR_CTL_LBREN BIT(0)
>> #define ARCH_LBR_CTL_CPL_OFFSET 1
>> #define ARCH_LBR_CTL_CPL (0x3ull << ARCH_LBR_CTL_CPL_OFFSET)
>> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
>> index 0ffaa3156a4e..ea3be961cc8e 100644
>> --- a/arch/x86/include/asm/vmx.h
>> +++ b/arch/x86/include/asm/vmx.h
>> @@ -245,6 +245,8 @@ enum vmcs_field {
>> GUEST_BNDCFGS_HIGH = 0x00002813,
>> GUEST_IA32_RTIT_CTL = 0x00002814,
>> GUEST_IA32_RTIT_CTL_HIGH = 0x00002815,
>> + GUEST_IA32_LBR_CTL = 0x00002816,
>> + GUEST_IA32_LBR_CTL_HIGH = 0x00002817,
>> HOST_IA32_PAT = 0x00002c00,
>> HOST_IA32_PAT_HIGH = 0x00002c01,
>> HOST_IA32_EFER = 0x00002c02,
>> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
>> index c8e6c1e1e00c..7dc8a5783df7 100644
>> --- a/arch/x86/kvm/vmx/pmu_intel.c
>> +++ b/arch/x86/kvm/vmx/pmu_intel.c
>> @@ -19,6 +19,7 @@
>> #include "pmu.h"
>>
>> #define MSR_PMC_FULL_WIDTH_BIT (MSR_IA32_PMC0 - MSR_IA32_PERFCTR0)
>> +#define KVM_ARCH_LBR_CTL_MASK (ARCH_LBR_CTL_MASK | ARCH_LBR_CTL_LBREN)
>>
>> static struct kvm_event_hw_type_mapping intel_arch_events[] = {
>> [0] = { 0x3c, 0x00, PERF_COUNT_HW_CPU_CYCLES },
>> @@ -215,6 +216,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
>> ret = pmu->version > 1;
>> break;
>> case MSR_ARCH_LBR_DEPTH:
>> + case MSR_ARCH_LBR_CTL:
>> if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
>> ret = guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR);
>> break;
>> @@ -361,6 +363,35 @@ static bool arch_lbr_depth_is_valid(struct kvm_vcpu *vcpu, u64 depth)
>> return (depth == pmu->kvm_arch_lbr_depth);
>> }
>>
>> +#define ARCH_LBR_CTL_BRN_MASK GENMASK_ULL(22, 16)
>> +
>> +static bool arch_lbr_ctl_is_valid(struct kvm_vcpu *vcpu, u64 ctl)
>> +{
>> + struct kvm_cpuid_entry2 *entry;
>> +
>> + if (!kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
>> + return false;
>> +
>> + if (ctl & ~KVM_ARCH_LBR_CTL_MASK)
>> + goto warn;
>> +
>> + entry = kvm_find_cpuid_entry(vcpu, 0x1c, 0);
>> + if (!entry)
>> + return false;
>> +
>> + if (!(entry->ebx & BIT(0)) && (ctl & ARCH_LBR_CTL_CPL))
>> + return false;
>> + if (!(entry->ebx & BIT(2)) && (ctl & ARCH_LBR_CTL_STACK))
>> + return false;
>> + if (!(entry->ebx & BIT(1)) && (ctl & ARCH_LBR_CTL_BRN_MASK))
> Why KVM wants to define this mask by itself? Cannot we use the
> ARCH_LBR_CTL_FILTER?
Thanks Ken for review!
Sounds like the ISE has been updated, per section "CPUID for Ach LBRs":
EBX 1 Branch Filtering Supported If set, the processor supports setting
IA32_LBR_CTL[22:16] to non-zero value.
but the FILTER definition looks like:
#define ARCH_LBR_CTL_FILTER_OFFSET 16
#define ARCH_LBR_CTL_FILTER (0x7full <<
ARCH_LBR_CTL_FILTER_OFFSET)
Maybe I need to update the FILTER and re-use it.
>
> Thanks,
> Kan
>
>> + return false;
>> + return true;
>> +warn:
>> + pr_warn_ratelimited("kvm: vcpu-%d: invalid arch lbr ctl.\n",
>> + vcpu->vcpu_id);
>> + return false;
>> +}
>> +
>> static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> {
>> struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
>> @@ -384,6 +415,9 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> case MSR_ARCH_LBR_DEPTH:
>> msr_info->data = lbr_desc->records.nr;
>> return 0;
>> + case MSR_ARCH_LBR_CTL:
>> + msr_info->data = vmcs_read64(GUEST_IA32_LBR_CTL);
>> + return 0;
>> default:
>> if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
>> (pmc = get_gp_pmc(pmu, msr, MSR_IA32_PMC0))) {
>> @@ -455,6 +489,16 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> */
>> wrmsrl(MSR_ARCH_LBR_DEPTH, lbr_desc->records.nr);
>> return 0;
>> + case MSR_ARCH_LBR_CTL:
>> + if (!arch_lbr_ctl_is_valid(vcpu, data))
>> + break;
>> +
>> + vmcs_write64(GUEST_IA32_LBR_CTL, data);
>> +
>> + if (intel_pmu_lbr_is_enabled(vcpu) && !lbr_desc->event &&
>> + (data & ARCH_LBR_CTL_LBREN))
>> + intel_pmu_create_guest_lbr_event(vcpu);
>> + return 0;
>> default:
>> if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
>> (pmc = get_gp_pmc(pmu, msr, MSR_IA32_PMC0))) {
>> @@ -668,12 +712,16 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
>> */
>> static void intel_pmu_legacy_freezing_lbrs_on_pmi(struct kvm_vcpu *vcpu)
>> {
>> - u64 data = vmcs_read64(GUEST_IA32_DEBUGCTL);
>> + u32 lbr_ctl_field = GUEST_IA32_DEBUGCTL;
>>
>> - if (data & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI) {
>> - data &= ~DEBUGCTLMSR_LBR;
>> - vmcs_write64(GUEST_IA32_DEBUGCTL, data);
>> - }
>> + if (!(vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI))
>> + return;
>> +
>> + if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR) &&
>> + guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
>> + lbr_ctl_field = GUEST_IA32_LBR_CTL;
>> +
>> + vmcs_write64(lbr_ctl_field, vmcs_read64(lbr_ctl_field) & ~0x1ULL);
>> }
>>
>> static void intel_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 04d170c4b61e..73961fcfb62d 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -2022,6 +2022,13 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> VM_EXIT_SAVE_DEBUG_CONTROLS)
>> get_vmcs12(vcpu)->guest_ia32_debugctl = data;
>>
>> + /*
>> + * For Arch LBR, IA32_DEBUGCTL[bit 0] has no meaning.
>> + * It can be written to 0 or 1, but reads will always return 0.
>> + */
>> + if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
>> + data &= ~DEBUGCTLMSR_LBR;
>> +
>> vmcs_write64(GUEST_IA32_DEBUGCTL, data);
>> if (intel_pmu_lbr_is_enabled(vcpu) && !to_vmx(vcpu)->lbr_desc.event &&
>> (data & DEBUGCTLMSR_LBR))
>> @@ -4548,6 +4555,11 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>> kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
>>
>> vpid_sync_context(vmx->vpid);
>> +
>> + if (!init_event) {
>> + if (static_cpu_has(X86_FEATURE_ARCH_LBR))
>> + vmcs_write64(GUEST_IA32_LBR_CTL, 0);
>> + }
>> }
>>
>> static void vmx_enable_irq_window(struct kvm_vcpu *vcpu)
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