[PATCH 1/9] perf x86: Add precise sysfs cpu pmu attribute

[Jiri Olsa]

Adding sysfs 'precise' attribute for cpu device
(/sys/devices/cpu/precise) to show the maximum
value for perf event precise_ip attribute.

This will be used to put proper precise_ip when
configuring an event and and to automatically test
precise stuff to some extend.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/perf_event.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 5ed7a4c..d38c9ea 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -377,19 +377,26 @@ static inline int precise_br_compat(struct perf_event *event)
 	return m == b;
 }
 
-int x86_pmu_hw_config(struct perf_event *event)
+static int x86_get_precise(void)
 {
-	if (event->attr.precise_ip) {
-		int precise = 0;
+	int precise = 0;
 
-		/* Support for constant skid */
-		if (x86_pmu.pebs_active && !x86_pmu.pebs_broken) {
+	/* Support for constant skid */
+	if (x86_pmu.pebs_active && !x86_pmu.pebs_broken) {
+		precise++;
+
+		/* Support for IP fixup */
+		if (x86_pmu.lbr_nr)
 			precise++;
+	}
 
-			/* Support for IP fixup */
-			if (x86_pmu.lbr_nr)
-				precise++;
-		}
+	return precise;
+}
+
+int x86_pmu_hw_config(struct perf_event *event)
+{
+	if (event->attr.precise_ip) {
+		int precise = x86_get_precise();
 
 		if (event->attr.precise_ip > precise)
 			return -EOPNOTSUPP;
@@ -1734,6 +1741,13 @@ static int x86_pmu_event_init(struct perf_event *event)
 	return err;
 }
 
+static ssize_t get_attr_precise(struct device *cdev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	return snprintf(buf, 10, "%d\n", x86_get_precise());
+}
+
 static int x86_pmu_event_idx(struct perf_event *event)
 {
 	int idx = event->hw.idx;
@@ -1786,9 +1800,11 @@ static ssize_t set_attr_rdpmc(struct device *cdev,
 }
 
 static DEVICE_ATTR(rdpmc, S_IRUSR | S_IWUSR, get_attr_rdpmc, set_attr_rdpmc);
+static DEVICE_ATTR(precise, S_IRUGO, get_attr_precise, NULL);
 
 static struct attribute *x86_pmu_attrs[] = {
 	&dev_attr_rdpmc.attr,
+	&dev_attr_precise.attr,
 	NULL,
 };
 
-- 
1.7.11.7

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