perf/core: Provide a kernel-internal interface to recalibrate event period
Currently, perf_event_period() is used by user tools via ioctl. Based on
naming convention, exporting perf_event_period() for kernel users (such
as KVM) who may recalibrate the event period for their assigned counter
according to their requirements.
The perf_event_period() is an external accessor, just like the
perf_event_{en,dis}able() and should thus use perf_event_ctx_lock().
Suggested-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Like Xu <like.xu@linux.intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9ec0b0b..e1b83d2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5106,16 +5106,11 @@ static int perf_event_check_period(struct perf_event *event, u64 value)
return event->pmu->check_period(event, value);
}
-static int perf_event_period(struct perf_event *event, u64 __user *arg)
+static int _perf_event_period(struct perf_event *event, u64 value)
{
- u64 value;
-
if (!is_sampling_event(event))
return -EINVAL;
- if (copy_from_user(&value, arg, sizeof(value)))
- return -EFAULT;
-
if (!value)
return -EINVAL;
@@ -5133,6 +5128,19 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg)
return 0;
}
+int perf_event_period(struct perf_event *event, u64 value)
+{
+ struct perf_event_context *ctx;
+ int ret;
+
+ ctx = perf_event_ctx_lock(event);
+ ret = _perf_event_period(event, value);
+ perf_event_ctx_unlock(event, ctx);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(perf_event_period);
+
static const struct file_operations perf_fops;
static inline int perf_fget_light(int fd, struct fd *p)
@@ -5176,8 +5184,14 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
return _perf_event_refresh(event, arg);
case PERF_EVENT_IOC_PERIOD:
- return perf_event_period(event, (u64 __user *)arg);
+ {
+ u64 value;
+ if (copy_from_user(&value, (u64 __user *)arg, sizeof(value)))
+ return -EFAULT;
+
+ return _perf_event_period(event, value);
+ }
case PERF_EVENT_IOC_ID:
{
u64 id = primary_event_id(event);
