Commit 3ca270fc authored by Like Xu's avatar Like Xu Committed by Paolo Bonzini
Browse files

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: default avatarKan Liang <kan.liang@linux.intel.com>
Signed-off-by: default avatarLike Xu <like.xu@linux.intel.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 02d496cf

include/linux/perf_event.h

+5 −0
Original line number Diff line number Diff line
@@ -1336,6 +1336,7 @@ extern void perf_event_disable_local(struct perf_event *event); 
extern void perf_event_disable_inatomic(struct perf_event *event);

extern void perf_event_task_tick(void);

extern int perf_event_account_interrupt(struct perf_event *event);

extern int perf_event_period(struct perf_event *event, u64 value);

#else /* !CONFIG_PERF_EVENTS: */

static inline void *

perf_aux_output_begin(struct perf_output_handle *handle,
@@ -1415,6 +1416,10 @@ static inline void perf_event_disable(struct perf_event *event) { } 
static inline int __perf_event_disable(void *info)			{ return -1; }

static inline void perf_event_task_tick(void)				{ }

static inline int perf_event_release_kernel(struct perf_event *event)	{ return 0; }

static inline int perf_event_period(struct perf_event *event, u64 value)

{

	return -EINVAL;

}

#endif



#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)

kernel/events/core.c

+21 −7
Original line number Diff line number Diff line
@@ -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);