[PATCH v9 09/10] KVM: x86: Expose MSR_IA32_PERF_CAPABILITIES to guest for LBR record format

Like Xu
2020-03-13T02:19:31Z

The MSR_IA32_PERF_CAPABILITIES is a read only MSR that enumerates the
existence of performance monitoring features. Bits [0, 5] of it tells
about the LBR format of the branch record addresses stored in the LBR
stack. Expose those bits to the guest when the guest LBR is enabled.

Cc: Luwei Kang <luwei.kang@intel.com>
Co-developed-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/cpuid.c | 3 ++-
arch/x86/kvm/pmu.h | 9 +++++++++
arch/x86/kvm/vmx/pmu_intel.c | 28 ++++++++++++++++++++++++++++
4 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b4c1761ca783..d915eedcbe43 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -483,6 +483,7 @@ struct kvm_pmu {
u64 global_ctrl_mask;
u64 global_ovf_ctrl_mask;
u64 reserved_bits;
+ u64 perf_capabilities;
u8 version;
struct kvm_pmc gp_counters[INTEL_PMC_MAX_GENERIC];
struct kvm_pmc fixed_counters[INTEL_PMC_MAX_FIXED];
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b1c469446b07..55f57d6c3de0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -446,6 +446,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0;
unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0;
+ unsigned int f_pdcm = kvm_pmu_get_perf_capabilities() ? F(PDCM) : 0;

/* cpuid 1.edx */
const u32 kvm_cpuid_1_edx_x86_features =
@@ -474,7 +475,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
0 /* DS-CPL, VMX, SMX, EST */ |
0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
- F(FMA) | F(CX16) | 0 /* xTPR Update, PDCM */ |
+ F(FMA) | F(CX16) | 0 /* xTPR Update*/ | f_pdcm |
F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) |
F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) |
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index d4ef7ec3331d..1cf73f39335d 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -43,6 +43,7 @@ struct kvm_pmu_ops {
bool (*lbr_setup)(struct kvm_vcpu *vcpu);
void (*lbr_cleanup)(struct kvm_vcpu *vcpu);
void (*availability_check)(struct kvm_vcpu *vcpu);
+ u64 (*get_perf_capabilities)(void);
};

static inline bool event_is_oncpu(struct perf_event *event)
@@ -149,6 +150,14 @@ static inline u64 get_sample_period(struct kvm_pmc *pmc, u64 counter_value)
return sample_period;
}

+static inline u64 kvm_pmu_get_perf_capabilities(void)
+{
+ if (kvm_x86_ops->pmu_ops->get_perf_capabilities)
+ return kvm_x86_ops->pmu_ops->get_perf_capabilities();
+
+ return 0;
+}
+
void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel);
void reprogram_fixed_counter(struct kvm_pmc *pmc, u8 ctrl, int fixed_idx);
void reprogram_counter(struct kvm_pmu *pmu, int pmc_idx);
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index bbb5f4c63f52..167061ce0434 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -19,6 +19,8 @@
#include "pmu.h"
#include "vmx.h"

+#define X86_PERF_CAP_MASK_LBR_FMT 0x3f
+
static struct kvm_event_hw_type_mapping intel_arch_events[] = {
/* Index must match CPUID 0x0A.EBX bit vector */
[0] = { 0x3c, 0x00, PERF_COUNT_HW_CPU_CYCLES },
@@ -182,6 +184,9 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
case MSR_IA32_DEBUGCTLMSR:
ret = pmu->version > 1;
break;
+ case MSR_IA32_PERF_CAPABILITIES:
+ ret = guest_cpuid_has(vcpu, X86_FEATURE_PDCM);
+ break;
default:
ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||
get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0) ||
@@ -342,6 +347,9 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_IA32_DEBUGCTLMSR:
msr_info->data = vmcs_read64(GUEST_IA32_DEBUGCTL);
return 0;
+ case MSR_IA32_PERF_CAPABILITIES:
+ msr_info->data = pmu->perf_capabilities;
+ return 0;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
u64 val = pmc_read_counter(pmc);
@@ -419,6 +427,8 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (pmu->lbr_event)
__set_bit(KVM_PMU_LBR_IN_USE_IDX, pmu->pmc_in_use);
return 0;
+ case MSR_IA32_PERF_CAPABILITIES:
+ return 1; /* RO MSR */
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
if (!msr_info->host_initiated)
@@ -448,6 +458,19 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
}

+static u64 intel_pmu_get_perf_capabilities(void)
+{
+ u64 perf_cap = 0;
+
+ if (boot_cpu_has(X86_FEATURE_PDCM))
+ rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);
+
+ /* Currently, KVM only support LBR. */
+ perf_cap &= X86_PERF_CAP_MASK_LBR_FMT;
+
+ return perf_cap;
+}
+
static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
{
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -474,6 +497,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
return;

perf_get_x86_pmu_capability(&x86_pmu);
+ pmu->perf_capabilities = intel_pmu_get_perf_capabilities();

pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
x86_pmu.num_counters_gp);
@@ -501,6 +525,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
pmu->global_ovf_ctrl_mask &=
~MSR_CORE_PERF_GLOBAL_OVF_CTRL_TRACE_TOPA_PMI;

+ if (!vcpu->kvm->arch.lbr_in_guest)
+ pmu->perf_capabilities &= ~X86_PERF_CAP_MASK_LBR_FMT;
+
entry = kvm_find_cpuid_entry(vcpu, 7, 0);
if (entry &&
(boot_cpu_has(X86_FEATURE_HLE) || boot_cpu_has(X86_FEATURE_RTM)) &&
@@ -652,4 +679,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
.lbr_setup = intel_pmu_setup_lbr,
.availability_check = intel_pmu_availability_check,
.lbr_cleanup = intel_pmu_cleanup_lbr,
+ .get_perf_capabilities = intel_pmu_get_perf_capabilities,
};
--
2.21.1