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perf/core: Provide a kernel-internal interface to recalibrate event period

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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>
This commit is contained in:
Like Xu 2019-10-27 18:52:38 +08:00 committed by Paolo Bonzini
parent 02d496cfb8
commit 3ca270fc9e
2 changed files with 26 additions and 7 deletions
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5
include/linux/perf_event.h
View file

@ -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)

28
kernel/events/core.c
View file

@ -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);