drivers/perf: apple_m1: Provide helper for mapping PMUv3 events

Apple M* parts carry some IMP DEF traps for guest accesses to PMUv3
registers, even though the underlying hardware doesn't implement PMUv3.
This means it is possible to virtualize PMUv3 for KVM guests.

Add a helper for mapping common PMUv3 event IDs onto hardware event IDs,
keeping the implementation-specific crud in the PMU driver rather than
KVM proper.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: oupton

drivers/perf/apple_m1_cpu_pmu.c

@@ -12,6 +12,7 @@
 
 #include <linux/of.h>
 #include <linux/perf/arm_pmu.h>
+#include <linux/perf/arm_pmuv3.h>
 #include <linux/platform_device.h>
 
 #include <asm/apple_m1_pmu.h>
@@ -174,6 +175,14 @@ static const unsigned m1_pmu_perf_map[PERF_COUNT_HW_MAX] = {
 	[PERF_COUNT_HW_BRANCH_MISSES]		= M1_PMU_PERFCTR_BRANCH_MISPRED_NONSPEC,
 };
 
+#define M1_PMUV3_EVENT_MAP(pmuv3_event, m1_event)							\
+	[ARMV8_PMUV3_PERFCTR_##pmuv3_event]			= M1_PMU_PERFCTR_##m1_event
+
+static const unsigned int m1_pmu_pmceid_map[ARMV8_PMUV3_MAX_COMMON_EVENTS] = {
+	[0 ... ARMV8_PMUV3_MAX_COMMON_EVENTS - 1]	= HW_OP_UNSUPPORTED,
+	M1_PMUV3_EVENT_MAP(CPU_CYCLES,		CORE_ACTIVE_CYCLE),
+};
+
 /* sysfs definitions */
 static ssize_t m1_pmu_events_sysfs_show(struct device *dev,
 					struct device_attribute *attr,
@@ -558,6 +567,26 @@ static int m2_pmu_map_event(struct perf_event *event)
 	return armpmu_map_event(event, &m1_pmu_perf_map, NULL, M1_PMU_CFG_EVENT);
 }
 
+static int m1_pmu_map_pmuv3_event(unsigned int eventsel)
+{
+	int m1_event = HW_OP_UNSUPPORTED;
+
+	if (eventsel < ARMV8_PMUV3_MAX_COMMON_EVENTS)
+		m1_event = m1_pmu_pmceid_map[eventsel];
+
+	return m1_event == HW_OP_UNSUPPORTED ? -EOPNOTSUPP : m1_event;
+}
+
+static void m1_pmu_init_pmceid(struct arm_pmu *pmu)
+{
+	unsigned int event;
+
+	for (event = 0; event < ARMV8_PMUV3_MAX_COMMON_EVENTS; event++) {
+		if (m1_pmu_map_pmuv3_event(event) >= 0)
+			set_bit(event, pmu->pmceid_bitmap);
+	}
+}
+
 static void m1_pmu_reset(void *info)
 {
 	int i;
@@ -618,6 +647,9 @@ static int m1_pmu_init(struct arm_pmu *cpu_pmu, u32 flags)
 	cpu_pmu->reset		  = m1_pmu_reset;
 	cpu_pmu->set_event_filter = m1_pmu_set_event_filter;
 
+	cpu_pmu->map_pmuv3_event  = m1_pmu_map_pmuv3_event;
+	m1_pmu_init_pmceid(cpu_pmu);
+
 	bitmap_set(cpu_pmu->cntr_mask, 0, M1_PMU_NR_COUNTERS);
 	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_EVENTS] = &m1_pmu_events_attr_group;
 	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_FORMATS] = &m1_pmu_format_attr_group;

include/linux/perf/arm_pmu.h

@@ -100,6 +100,7 @@ struct arm_pmu {
 	void		(*stop)(struct arm_pmu *);
 	void		(*reset)(void *);
 	int		(*map_event)(struct perf_event *event);
+	int		(*map_pmuv3_event)(unsigned int eventsel);
 	DECLARE_BITMAP(cntr_mask, ARMPMU_MAX_HWEVENTS);
 	bool		secure_access; /* 32-bit ARM only */
 #define ARMV8_PMUV3_MAX_COMMON_EVENTS		0x40