perf/x86: Add a x86_pmu::limit_period static_call

Avoid a branch and indirect call.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220829101321.640658334@infradead.org

arch/x86/events/core.c

@@ -72,8 +72,9 @@ DEFINE_STATIC_CALL_NULL(x86_pmu_add,  *x86_pmu.add);
 DEFINE_STATIC_CALL_NULL(x86_pmu_del,  *x86_pmu.del);
 DEFINE_STATIC_CALL_NULL(x86_pmu_read, *x86_pmu.read);
 
-DEFINE_STATIC_CALL_NULL(x86_pmu_set_period, *x86_pmu.set_period);
-DEFINE_STATIC_CALL_NULL(x86_pmu_update,     *x86_pmu.update);
+DEFINE_STATIC_CALL_NULL(x86_pmu_set_period,   *x86_pmu.set_period);
+DEFINE_STATIC_CALL_NULL(x86_pmu_update,       *x86_pmu.update);
+DEFINE_STATIC_CALL_NULL(x86_pmu_limit_period, *x86_pmu.limit_period);
 
 DEFINE_STATIC_CALL_NULL(x86_pmu_schedule_events,       *x86_pmu.schedule_events);
 DEFINE_STATIC_CALL_NULL(x86_pmu_get_event_constraints, *x86_pmu.get_event_constraints);
@@ -1396,8 +1397,7 @@ int x86_perf_event_set_period(struct perf_event *event)
 	if (left > x86_pmu.max_period)
 		left = x86_pmu.max_period;
 
-	if (x86_pmu.limit_period)
-		x86_pmu.limit_period(event, &left);
+	static_call_cond(x86_pmu_limit_period)(event, &left);
 
 	this_cpu_write(pmc_prev_left[idx], left);
 
@@ -2024,6 +2024,7 @@ static void x86_pmu_static_call_update(void)
 
 	static_call_update(x86_pmu_set_period, x86_pmu.set_period);
 	static_call_update(x86_pmu_update, x86_pmu.update);
+	static_call_update(x86_pmu_limit_period, x86_pmu.limit_period);
 
 	static_call_update(x86_pmu_schedule_events, x86_pmu.schedule_events);
 	static_call_update(x86_pmu_get_event_constraints, x86_pmu.get_event_constraints);