perf/x86/uncore: Support per PMU cpumask

The cpumask of some uncore units, e.g., CXL uncore units, may be wrong
under some configurations. Perf may access an uncore counter of a
non-existent uncore unit.

The uncore driver assumes that all uncore units are symmetric among
dies. A global cpumask is shared among all uncore PMUs. However, some
CXL uncore units may only be available on some dies.

A per PMU cpumask is introduced to track the CPU mask of this PMU.
The driver searches the unit control RB tree to check whether the PMU is
available on a given die, and updates the per PMU cpumask accordingly.

Signed-off-by: Kan Liang <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Yunying Sun <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Kan Liang

arch/x86/events/intel/uncore.c

@@ -843,7 +843,9 @@ static void uncore_pmu_disable(struct pmu *pmu)
 static ssize_t uncore_get_attr_cpumask(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
-	return cpumap_print_to_pagebuf(true, buf, &uncore_cpu_mask);
+	struct intel_uncore_pmu *pmu = container_of(dev_get_drvdata(dev), struct intel_uncore_pmu, pmu);
+
+	return cpumap_print_to_pagebuf(true, buf, &pmu->cpu_mask);
 }
 
 static DEVICE_ATTR(cpumask, S_IRUGO, uncore_get_attr_cpumask, NULL);
@@ -1453,6 +1455,18 @@ static void uncore_pci_exit(void)
 	}
 }
 
+static bool uncore_die_has_box(struct intel_uncore_type *type,
+			       int die, unsigned int pmu_idx)
+{
+	if (!type->boxes)
+		return true;
+
+	if (intel_uncore_find_discovery_unit_id(type->boxes, die, pmu_idx) < 0)
+		return false;
+
+	return true;
+}
+
 static void uncore_change_type_ctx(struct intel_uncore_type *type, int old_cpu,
 				   int new_cpu)
 {
@@ -1468,18 +1482,25 @@ static void uncore_change_type_ctx(struct intel_uncore_type *type, int old_cpu,
 
 		if (old_cpu < 0) {
 			WARN_ON_ONCE(box->cpu != -1);
-			box->cpu = new_cpu;
+			if (uncore_die_has_box(type, die, pmu->pmu_idx)) {
+				box->cpu = new_cpu;
+				cpumask_set_cpu(new_cpu, &pmu->cpu_mask);
+			}
 			continue;
 		}
 
-		WARN_ON_ONCE(box->cpu != old_cpu);
+		WARN_ON_ONCE(box->cpu != -1 && box->cpu != old_cpu);
 		box->cpu = -1;
+		cpumask_clear_cpu(old_cpu, &pmu->cpu_mask);
 		if (new_cpu < 0)
 			continue;
 
+		if (!uncore_die_has_box(type, die, pmu->pmu_idx))
+			continue;
 		uncore_pmu_cancel_hrtimer(box);
 		perf_pmu_migrate_context(&pmu->pmu, old_cpu, new_cpu);
 		box->cpu = new_cpu;
+		cpumask_set_cpu(new_cpu, &pmu->cpu_mask);
 	}
 }
 
@@ -1502,7 +1523,7 @@ static void uncore_box_unref(struct intel_uncore_type **types, int id)
 		pmu = type->pmus;
 		for (i = 0; i < type->num_boxes; i++, pmu++) {
 			box = pmu->boxes[id];
-			if (box && atomic_dec_return(&box->refcnt) == 0)
+			if (box && box->cpu >= 0 && atomic_dec_return(&box->refcnt) == 0)
 				uncore_box_exit(box);
 		}
 	}
@@ -1592,7 +1613,7 @@ static int uncore_box_ref(struct intel_uncore_type **types,
 		pmu = type->pmus;
 		for (i = 0; i < type->num_boxes; i++, pmu++) {
 			box = pmu->boxes[id];
-			if (box && atomic_inc_return(&box->refcnt) == 1)
+			if (box && box->cpu >= 0 && atomic_inc_return(&box->refcnt) == 1)
 				uncore_box_init(box);
 		}
 	}

arch/x86/events/intel/uncore.h

@@ -86,6 +86,7 @@ struct intel_uncore_type {
 	const struct attribute_group *attr_groups[4];
 	const struct attribute_group **attr_update;
 	struct pmu *pmu; /* for custom pmu ops */
+	struct rb_root *boxes;
 	/*
 	 * Uncore PMU would store relevant platform topology configuration here
 	 * to identify which platform component each PMON block of that type is
@@ -125,6 +126,7 @@ struct intel_uncore_pmu {
 	int				func_id;
 	bool				registered;
 	atomic_t			activeboxes;
+	cpumask_t			cpu_mask;
 	struct intel_uncore_type	*type;
 	struct intel_uncore_box		**boxes;
 };

arch/x86/events/intel/uncore_discovery.c

@@ -122,6 +122,64 @@ get_uncore_discovery_type(struct uncore_unit_discovery *unit)
 	return add_uncore_discovery_type(unit);
 }
 
+static inline int pmu_idx_cmp(const void *key, const struct rb_node *b)
+{
+	struct intel_uncore_discovery_unit *unit;
+	const unsigned int *id = key;
+
+	unit = rb_entry(b, struct intel_uncore_discovery_unit, node);
+
+	if (unit->pmu_idx > *id)
+		return -1;
+	else if (unit->pmu_idx < *id)
+		return 1;
+
+	return 0;
+}
+
+static struct intel_uncore_discovery_unit *
+intel_uncore_find_discovery_unit(struct rb_root *units, int die,
+				 unsigned int pmu_idx)
+{
+	struct intel_uncore_discovery_unit *unit;
+	struct rb_node *pos;
+
+	if (!units)
+		return NULL;
+
+	pos = rb_find_first(&pmu_idx, units, pmu_idx_cmp);
+	if (!pos)
+		return NULL;
+	unit = rb_entry(pos, struct intel_uncore_discovery_unit, node);
+
+	if (die < 0)
+		return unit;
+
+	for (; pos; pos = rb_next(pos)) {
+		unit = rb_entry(pos, struct intel_uncore_discovery_unit, node);
+
+		if (unit->pmu_idx != pmu_idx)
+			break;
+
+		if (unit->die == die)
+			return unit;
+	}
+
+	return NULL;
+}
+
+int intel_uncore_find_discovery_unit_id(struct rb_root *units, int die,
+					unsigned int pmu_idx)
+{
+	struct intel_uncore_discovery_unit *unit;
+
+	unit = intel_uncore_find_discovery_unit(units, die, pmu_idx);
+	if (unit)
+		return unit->id;
+
+	return -1;
+}
+
 static inline bool unit_less(struct rb_node *a, const struct rb_node *b)
 {
 	struct intel_uncore_discovery_unit *a_node, *b_node;

arch/x86/events/intel/uncore_discovery.h

@@ -166,3 +166,6 @@ u64 intel_generic_uncore_pci_read_counter(struct intel_uncore_box *box,
 
 struct intel_uncore_type **
 intel_uncore_generic_init_uncores(enum uncore_access_type type_id, int num_extra);
+
+int intel_uncore_find_discovery_unit_id(struct rb_root *units, int die,
+					unsigned int pmu_idx);