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Message-ID: <bc3b3f6c-8d68-ffc1-cb6e-604d84797da1@linux.intel.com>
Date: Thu, 28 Apr 2022 10:16:36 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Yang Weijiang <weijiang.yang@...el.com>, pbonzini@...hat.com,
jmattson@...gle.com, seanjc@...gle.com, like.xu.linux@...il.com,
vkuznets@...hat.com, wei.w.wang@...el.com, kvm@...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 4/22/2022 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,
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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