[PATCH 1/6] perf, x86: Making hardware events translations available in sysfs

[Jiri Olsa <jolsa@redhat.com>]

Making hardware events translations available through the sysfs.
Adding 'events' group attribute under the sysfs x86 PMU record
with attribute/file for each hardware event:

  # ls  /sys/devices/cpu/events/
  branch-instructions
  branch-misses
  bus-cycles
  cache-misses
  cache-references
  cpu-cycles
  instructions
  ref-cycles
  stalled-cycles-backend
  stalled-cycles-frontend

The file - hw event ID mappings is:

  file                      hw event ID
  ---------------------------------------------------------------
  cpu-cycles                PERF_COUNT_HW_CPU_CYCLES
  instructions              PERF_COUNT_HW_INSTRUCTIONS
  cache-references          PERF_COUNT_HW_CACHE_REFERENCES
  cache-misses              PERF_COUNT_HW_CACHE_MISSES
  branch-instructions       PERF_COUNT_HW_BRANCH_INSTRUCTIONS
  branch-misses             PERF_COUNT_HW_BRANCH_MISSES
  bus-cycles                PERF_COUNT_HW_BUS_CYCLES
  stalled-cycles-frontend   PERF_COUNT_HW_STALLED_CYCLES_FRONTEND
  stalled-cycles-backend    PERF_COUNT_HW_STALLED_CYCLES_BACKEND
  ref-cycles                PERF_COUNT_HW_REF_CPU_CYCLES

Each file in 'events' directory contains term translation for the
symbolic hw event for the currently running cpu model.

  # cat /sys/devices/cpu/events/stalled-cycles-backend
  event=0xb1,umask=0x01,inv,cmask=0x01

Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
---
 arch/x86/kernel/cpu/perf_event.c |   74 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 29557aa..09452c2 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1638,9 +1638,83 @@ static struct attribute_group x86_pmu_attr_group = {
 	.attrs = x86_pmu_attrs,
 };
 
+static ssize_t event_sysfs_data(char *page, u64 config)
+{
+	u64 event  = (config & ARCH_PERFMON_EVENTSEL_EVENT) |
+		     (config & AMD64_EVENTSEL_EVENT) >> 24;
+	u64 umask  = (config & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
+	u64 inv    = (config & ARCH_PERFMON_EVENTSEL_INV) >> 23;
+	u64 cmask  = (config & ARCH_PERFMON_EVENTSEL_CMASK) >> 24;
+	ssize_t ret;
+
+	/*
+	 * We have whole page size to spend and just little data
+	 * to write, so we can safely use sprintf.
+	 */
+	ret = sprintf(page, "event=0x%02llx", event);
+
+	if (umask)
+		ret += sprintf(page + ret, ",umask=0x%02llx", umask);
+
+	if (inv)
+		ret += sprintf(page + ret, ",inv");
+
+	if (cmask)
+		ret += sprintf(page + ret, ",cmask=0x%02llx", cmask);
+
+	ret += sprintf(page + ret, "\n");
+
+	return ret;
+}
+
+#define PMU_EVENTS_ATTR(_name, _id)			\
+static ssize_t						\
+_id##_show(struct device *dev,				\
+	   struct device_attribute *attr,		\
+	   char *page)					\
+{							\
+	u64 config = x86_pmu.event_map(_id);		\
+	BUILD_BUG_ON(_id >= PERF_COUNT_HW_MAX);		\
+	return event_sysfs_data(page, config);		\
+}							\
+							\
+static struct device_attribute event_attr_##_id =	\
+	__ATTR(_name, 0444, _id##_show, NULL)
+
+PMU_EVENTS_ATTR(cpu-cycles, PERF_COUNT_HW_CPU_CYCLES);
+PMU_EVENTS_ATTR(instructions, PERF_COUNT_HW_INSTRUCTIONS);
+PMU_EVENTS_ATTR(cache-references, PERF_COUNT_HW_CACHE_REFERENCES);
+PMU_EVENTS_ATTR(cache-misses, PERF_COUNT_HW_CACHE_MISSES);
+PMU_EVENTS_ATTR(branch-instructions, PERF_COUNT_HW_BRANCH_INSTRUCTIONS);
+PMU_EVENTS_ATTR(branch-misses, PERF_COUNT_HW_BRANCH_MISSES);
+PMU_EVENTS_ATTR(bus-cycles, PERF_COUNT_HW_BUS_CYCLES);
+PMU_EVENTS_ATTR(stalled-cycles-frontend, PERF_COUNT_HW_STALLED_CYCLES_FRONTEND);
+PMU_EVENTS_ATTR(stalled-cycles-backend, PERF_COUNT_HW_STALLED_CYCLES_BACKEND);
+PMU_EVENTS_ATTR(ref-cycles, PERF_COUNT_HW_REF_CPU_CYCLES);
+
+static struct attribute *events_attr[] = {
+	&event_attr_PERF_COUNT_HW_CPU_CYCLES.attr,
+	&event_attr_PERF_COUNT_HW_INSTRUCTIONS.attr,
+	&event_attr_PERF_COUNT_HW_CACHE_REFERENCES.attr,
+	&event_attr_PERF_COUNT_HW_CACHE_MISSES.attr,
+	&event_attr_PERF_COUNT_HW_BRANCH_INSTRUCTIONS.attr,
+	&event_attr_PERF_COUNT_HW_BRANCH_MISSES.attr,
+	&event_attr_PERF_COUNT_HW_BUS_CYCLES.attr,
+	&event_attr_PERF_COUNT_HW_STALLED_CYCLES_FRONTEND.attr,
+	&event_attr_PERF_COUNT_HW_STALLED_CYCLES_BACKEND.attr,
+	&event_attr_PERF_COUNT_HW_REF_CPU_CYCLES.attr,
+	NULL,
+};
+
+static struct attribute_group x86_pmu_events_group = {
+	.name = "events",
+	.attrs = events_attr,
+};
+
 static const struct attribute_group *x86_pmu_attr_groups[] = {
 	&x86_pmu_attr_group,
 	&x86_pmu_format_group,
+	&x86_pmu_events_group,
 	NULL,
 };
 
-- 
1.7.10.4