Hypervisors may create an lbr event for a vcpu's lbr emulation, and the emulation doesn't need a counter fundamentally. This makes the emulation follow the x86 SDM's description about lbr, which doesn't include a counter, and also avoids wasting a counter.
The perf scheduler is supported to not assign a counter for a perf event which doesn't need a counter. Define a macro, X86_PMC_IDX_NA, to replace "-1", which represents a never assigned counter id. Cc: Andi Kleen <a...@linux.intel.com> Cc: Peter Zijlstra <pet...@infradead.org> Signed-off-by: Wei Wang <wei.w.w...@intel.com> https://lkml.kernel.org/r/20180920162407.ga24...@hirez.programming.kicks-ass.net --- arch/x86/events/core.c | 36 +++++++++++++++++++++++++++--------- arch/x86/events/intel/core.c | 3 +++ arch/x86/include/asm/perf_event.h | 1 + include/linux/perf_event.h | 11 +++++++++++ 4 files changed, 42 insertions(+), 9 deletions(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 81b005e..ffa27bb 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -73,7 +73,7 @@ u64 x86_perf_event_update(struct perf_event *event) int idx = hwc->idx; u64 delta; - if (idx == INTEL_PMC_IDX_FIXED_BTS) + if ((idx == INTEL_PMC_IDX_FIXED_BTS) || (idx == X86_PMC_IDX_NA)) return 0; /* @@ -595,7 +595,7 @@ static int __x86_pmu_event_init(struct perf_event *event) atomic_inc(&active_events); event->destroy = hw_perf_event_destroy; - event->hw.idx = -1; + event->hw.idx = X86_PMC_IDX_NA; event->hw.last_cpu = -1; event->hw.last_tag = ~0ULL; @@ -763,6 +763,8 @@ static bool perf_sched_restore_state(struct perf_sched *sched) static bool __perf_sched_find_counter(struct perf_sched *sched) { struct event_constraint *c; + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); + struct perf_event *e = cpuc->event_list[sched->state.event]; int idx; if (!sched->state.unassigned) @@ -772,6 +774,14 @@ static bool __perf_sched_find_counter(struct perf_sched *sched) return false; c = sched->constraints[sched->state.event]; + if (c == &emptyconstraint) + return false; + + if (is_no_counter_event(e)) { + idx = X86_PMC_IDX_NA; + goto done; + } + /* Prefer fixed purpose counters */ if (c->idxmsk64 & (~0ULL << INTEL_PMC_IDX_FIXED)) { idx = INTEL_PMC_IDX_FIXED; @@ -797,7 +807,7 @@ static bool __perf_sched_find_counter(struct perf_sched *sched) done: sched->state.counter = idx; - if (c->overlap) + if ((idx != X86_PMC_IDX_NA) && c->overlap) perf_sched_save_state(sched); return true; @@ -918,7 +928,7 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign) c = cpuc->event_constraint[i]; /* never assigned */ - if (hwc->idx == -1) + if (hwc->idx == X86_PMC_IDX_NA) break; /* constraint still honored */ @@ -969,7 +979,8 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign) if (!unsched && assign) { for (i = 0; i < n; i++) { e = cpuc->event_list[i]; - if (x86_pmu.commit_scheduling) + if (x86_pmu.commit_scheduling && + (assign[i] != X86_PMC_IDX_NA)) x86_pmu.commit_scheduling(cpuc, i, assign[i]); } } else { @@ -1038,7 +1049,8 @@ static inline void x86_assign_hw_event(struct perf_event *event, hwc->last_cpu = smp_processor_id(); hwc->last_tag = ++cpuc->tags[i]; - if (hwc->idx == INTEL_PMC_IDX_FIXED_BTS) { + if ((hwc->idx == INTEL_PMC_IDX_FIXED_BTS) || + (hwc->idx == X86_PMC_IDX_NA)) { hwc->config_base = 0; hwc->event_base = 0; } else if (hwc->idx >= INTEL_PMC_IDX_FIXED) { @@ -1115,7 +1127,7 @@ static void x86_pmu_enable(struct pmu *pmu) * - running on same CPU as last time * - no other event has used the counter since */ - if (hwc->idx == -1 || + if (hwc->idx == X86_PMC_IDX_NA || match_prev_assignment(hwc, cpuc, i)) continue; @@ -1169,7 +1181,7 @@ int x86_perf_event_set_period(struct perf_event *event) s64 period = hwc->sample_period; int ret = 0, idx = hwc->idx; - if (idx == INTEL_PMC_IDX_FIXED_BTS) + if ((idx == INTEL_PMC_IDX_FIXED_BTS) || (idx == X86_PMC_IDX_NA)) return 0; /* @@ -1306,7 +1318,7 @@ static void x86_pmu_start(struct perf_event *event, int flags) if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED))) return; - if (WARN_ON_ONCE(idx == -1)) + if (idx == X86_PMC_IDX_NA) return; if (flags & PERF_EF_RELOAD) { @@ -1388,6 +1400,9 @@ void x86_pmu_stop(struct perf_event *event, int flags) struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); struct hw_perf_event *hwc = &event->hw; + if (hwc->idx == X86_PMC_IDX_NA) + return; + if (test_bit(hwc->idx, cpuc->active_mask)) { x86_pmu.disable(event); __clear_bit(hwc->idx, cpuc->active_mask); @@ -2128,6 +2143,9 @@ static int x86_pmu_event_idx(struct perf_event *event) if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED)) return 0; + if (idx == X86_PMC_IDX_NA) + return X86_PMC_IDX_NA; + if (x86_pmu.num_counters_fixed && idx >= INTEL_PMC_IDX_FIXED) { idx -= INTEL_PMC_IDX_FIXED; idx |= 1 << 30; diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 648260b5..177c321 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -2156,6 +2156,9 @@ static void intel_pmu_disable_event(struct perf_event *event) return; } + if (hwc->idx == X86_PMC_IDX_NA) + return; + cpuc->intel_ctrl_guest_mask &= ~(1ull << hwc->idx); cpuc->intel_ctrl_host_mask &= ~(1ull << hwc->idx); cpuc->intel_cp_status &= ~(1ull << hwc->idx); diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h index aa77da2..23ab90c 100644 --- a/arch/x86/include/asm/perf_event.h +++ b/arch/x86/include/asm/perf_event.h @@ -11,6 +11,7 @@ #define INTEL_PMC_IDX_FIXED 32 #define X86_PMC_IDX_MAX 64 +#define X86_PMC_IDX_NA -1 #define MSR_ARCH_PERFMON_PERFCTR0 0xc1 #define MSR_ARCH_PERFMON_PERFCTR1 0xc2 diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index e8ad3c5..2cae06a 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -530,6 +530,7 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *, */ #define PERF_EV_CAP_SOFTWARE BIT(0) #define PERF_EV_CAP_READ_ACTIVE_PKG BIT(1) +#define PERF_EV_CAP_NO_COUNTER BIT(2) #define SWEVENT_HLIST_BITS 8 #define SWEVENT_HLIST_SIZE (1 << SWEVENT_HLIST_BITS) @@ -1039,6 +1040,16 @@ static inline bool is_sampling_event(struct perf_event *event) return event->attr.sample_period != 0; } +static inline bool is_no_counter_event(struct perf_event *event) +{ + return !!(event->event_caps & PERF_EV_CAP_NO_COUNTER); +} + +static inline void perf_event_set_no_counter(struct perf_event *event) +{ + event->event_caps |= PERF_EV_CAP_NO_COUNTER; +} + /* * Return 1 for a software event, 0 for a hardware event */ -- 2.7.4
