perf/x86/intel: Support TopDown metrics on Ice Lake

Ice Lake supports the hardware TopDown metrics feature, which can free
up the scarce GP counters.

Update the event constraints for the metrics events. The metric counters
do not exist, which are mapped to a dummy offset. The sharing between
multiple users of the same metric without multiplexing is not allowed.

Implement set_topdown_event_period for Ice Lake. The values in
PERF_METRICS MSR are derived from the fixed counter 3. Both registers
should start from zero.

Implement update_topdown_event for Ice Lake. The metric is reported by
multiplying the metric (fraction) with slots. To maintain accurate
measurements, both registers are cleared for each update. The fixed
counter 3 should always be cleared before the PERF_METRICS.

Implement td_attr for the new metrics events and the new slots fixed
counter. Make them visible to the perf user tools.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200723171117.9918-11-kan.liang@linux.intel.com

2 files changed, 131 insertions, 0 deletions

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 4a436681f6ea..db833346c119 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -247,6 +247,10 @@ static struct event_constraint intel_icl_event_constraints[] = {
 	FIXED_EVENT_CONSTRAINT(0x003c, 1),	/* CPU_CLK_UNHALTED.CORE */
 	FIXED_EVENT_CONSTRAINT(0x0300, 2),	/* CPU_CLK_UNHALTED.REF */
 	FIXED_EVENT_CONSTRAINT(0x0400, 3),	/* SLOTS */
+	METRIC_EVENT_CONSTRAINT(INTEL_TD_METRIC_RETIRING, 0),
+	METRIC_EVENT_CONSTRAINT(INTEL_TD_METRIC_BAD_SPEC, 1),
+	METRIC_EVENT_CONSTRAINT(INTEL_TD_METRIC_FE_BOUND, 2),
+	METRIC_EVENT_CONSTRAINT(INTEL_TD_METRIC_BE_BOUND, 3),
 	INTEL_EVENT_CONSTRAINT_RANGE(0x03, 0x0a, 0xf),
 	INTEL_EVENT_CONSTRAINT_RANGE(0x1f, 0x28, 0xf),
 	INTEL_EVENT_CONSTRAINT(0x32, 0xf),	/* SW_PREFETCH_ACCESS.* */
@@ -309,6 +313,12 @@ EVENT_ATTR_STR_HT(topdown-recovery-bubbles, td_recovery_bubbles,
 EVENT_ATTR_STR_HT(topdown-recovery-bubbles.scale, td_recovery_bubbles_scale,
 	"4", "2");
 
+EVENT_ATTR_STR(slots,			slots,		"event=0x00,umask=0x4");
+EVENT_ATTR_STR(topdown-retiring,	td_retiring,	"event=0x00,umask=0x80");
+EVENT_ATTR_STR(topdown-bad-spec,	td_bad_spec,	"event=0x00,umask=0x81");
+EVENT_ATTR_STR(topdown-fe-bound,	td_fe_bound,	"event=0x00,umask=0x82");
+EVENT_ATTR_STR(topdown-be-bound,	td_be_bound,	"event=0x00,umask=0x83");
+
 static struct attribute *snb_events_attrs[] = {
 	EVENT_PTR(td_slots_issued),
 	EVENT_PTR(td_slots_retired),
@@ -2232,6 +2242,99 @@ static void intel_pmu_del_event(struct perf_event *event)
 		intel_pmu_pebs_del(event);
 }
 
+static int icl_set_topdown_event_period(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	s64 left = local64_read(&hwc->period_left);
+
+	/*
+	 * The values in PERF_METRICS MSR are derived from fixed counter 3.
+	 * Software should start both registers, PERF_METRICS and fixed
+	 * counter 3, from zero.
+	 * Clear PERF_METRICS and Fixed counter 3 in initialization.
+	 * After that, both MSRs will be cleared for each read.
+	 * Don't need to clear them again.
+	 */
+	if (left == x86_pmu.max_period) {
+		wrmsrl(MSR_CORE_PERF_FIXED_CTR3, 0);
+		wrmsrl(MSR_PERF_METRICS, 0);
+		local64_set(&hwc->period_left, 0);
+	}
+
+	perf_event_update_userpage(event);
+
+	return 0;
+}
+
+static inline u64 icl_get_metrics_event_value(u64 metric, u64 slots, int idx)
+{
+	u32 val;
+
+	/*
+	 * The metric is reported as an 8bit integer fraction
+	 * suming up to 0xff.
+	 * slots-in-metric = (Metric / 0xff) * slots
+	 */
+	val = (metric >> ((idx - INTEL_PMC_IDX_METRIC_BASE) * 8)) & 0xff;
+	return  mul_u64_u32_div(slots, val, 0xff);
+}
+
+static void __icl_update_topdown_event(struct perf_event *event,
+				       u64 slots, u64 metrics)
+{
+	int idx = event->hw.idx;
+	u64 delta;
+
+	if (is_metric_idx(idx))
+		delta = icl_get_metrics_event_value(metrics, slots, idx);
+	else
+		delta = slots;
+
+	local64_add(delta, &event->count);
+}
+
+/*
+ * Update all active Topdown events.
+ *
+ * The PERF_METRICS and Fixed counter 3 are read separately. The values may be
+ * modify by a NMI. PMU has to be disabled before calling this function.
+ */
+static u64 icl_update_topdown_event(struct perf_event *event)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	struct perf_event *other;
+	u64 slots, metrics;
+	int idx;
+
+	/* read Fixed counter 3 */
+	rdpmcl((3 | INTEL_PMC_FIXED_RDPMC_BASE), slots);
+	if (!slots)
+		return 0;
+
+	/* read PERF_METRICS */
+	rdpmcl(INTEL_PMC_FIXED_RDPMC_METRICS, metrics);
+
+	for_each_set_bit(idx, cpuc->active_mask, INTEL_PMC_IDX_TD_BE_BOUND + 1) {
+		if (!is_topdown_idx(idx))
+			continue;
+		other = cpuc->events[idx];
+		__icl_update_topdown_event(other, slots, metrics);
+	}
+
+	/*
+	 * Check and update this event, which may have been cleared
+	 * in active_mask e.g. x86_pmu_stop()
+	 */
+	if (event && !test_bit(event->hw.idx, cpuc->active_mask))
+		__icl_update_topdown_event(event, slots, metrics);
+
+	/* The fixed counter 3 has to be written before the PERF_METRICS. */
+	wrmsrl(MSR_CORE_PERF_FIXED_CTR3, 0);
+	wrmsrl(MSR_PERF_METRICS, 0);
+
+	return slots;
+}
+
 static void intel_pmu_read_topdown_event(struct perf_event *event)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
@@ -4480,6 +4583,15 @@ static struct attribute *icl_events_attrs[] = {
 	NULL,
 };
 
+static struct attribute *icl_td_events_attrs[] = {
+	EVENT_PTR(slots),
+	EVENT_PTR(td_retiring),
+	EVENT_PTR(td_bad_spec),
+	EVENT_PTR(td_fe_bound),
+	EVENT_PTR(td_be_bound),
+	NULL,
+};
+
 static struct attribute *icl_tsx_events_attrs[] = {
 	EVENT_PTR(tx_start),
 	EVENT_PTR(tx_abort),
@@ -5264,10 +5376,13 @@ __init int intel_pmu_init(void)
 			hsw_format_attr : nhm_format_attr;
 		extra_skl_attr = skl_format_attr;
 		mem_attr = icl_events_attrs;
+		td_attr = icl_td_events_attrs;
 		tsx_attr = icl_tsx_events_attrs;
 		x86_pmu.rtm_abort_event = X86_CONFIG(.event=0xca, .umask=0x02);
 		x86_pmu.lbr_pt_coexist = true;
 		intel_pmu_pebs_data_source_skl(pmem);
+		x86_pmu.update_topdown_event = icl_update_topdown_event;
+		x86_pmu.set_topdown_event_period = icl_set_topdown_event_period;
 		pr_cont("Icelake events, ");
 		name = "icelake";
 		break;
@@ -5387,6 +5502,9 @@ __init int intel_pmu_init(void)
 	if (x86_pmu.counter_freezing)
 		x86_pmu.handle_irq = intel_pmu_handle_irq_v4;
 
+	if (x86_pmu.intel_cap.perf_metrics)
+		x86_pmu.intel_ctrl |= 1ULL << GLOBAL_CTRL_EN_PERF_METRICS;
+
 	return 0;
 }
 
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index dea009ce0e4a..345442410a4d 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -407,6 +407,19 @@ struct cpu_hw_events {
 	EVENT_CONSTRAINT(c, (1ULL << (32+n)), FIXED_EVENT_FLAGS)
 
 /*
+ * The special metric counters do not actually exist. They are calculated from
+ * the combination of the FxCtr3 + MSR_PERF_METRICS.
+ *
+ * The special metric counters are mapped to a dummy offset for the scheduler.
+ * The sharing between multiple users of the same metric without multiplexing
+ * is not allowed, even though the hardware supports that in principle.
+ */
+
+#define METRIC_EVENT_CONSTRAINT(c, n)					\
+	EVENT_CONSTRAINT(c, (1ULL << (INTEL_PMC_IDX_METRIC_BASE + n)),	\
+			 INTEL_ARCH_EVENT_MASK)
+
+/*
  * Constraint on the Event code + UMask
  */
 #define INTEL_UEVENT_CONSTRAINT(c, n)	\