Powerpc/perf: Wire up PMI throttling

Commit 14c63f17 ("perf: Drop sample rate when sampling is too
slow") introduced a way to throttle PMU interrupts if we're spending
too much time just processing those. Wire up powerpc PMI handler to
use this infrastructure.

We have throttling of the *rate* of interrupts, but this adds
throttling based on the *time taken* to process the interrupts.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/perf/core-book3s.c

@@ -10,6 +10,7 @@
  */
 #include <linux/kernel.h>
 #include <linux/sched.h>
+#include <linux/sched/clock.h>
 #include <linux/perf_event.h>
 #include <linux/percpu.h>
 #include <linux/hardirq.h>
@@ -2166,7 +2167,7 @@ static bool pmc_overflow(unsigned long val)
 /*
  * Performance monitor interrupt stuff
  */
-static void perf_event_interrupt(struct pt_regs *regs)
+static void __perf_event_interrupt(struct pt_regs *regs)
 {
 	int i, j;
 	struct cpu_hw_events *cpuhw = this_cpu_ptr(&cpu_hw_events);
@@ -2250,6 +2251,14 @@ static void perf_event_interrupt(struct pt_regs *regs)
 		irq_exit();
 }
 
+static void perf_event_interrupt(struct pt_regs *regs)
+{
+	u64 start_clock = sched_clock();
+
+	__perf_event_interrupt(regs);
+	perf_sample_event_took(sched_clock() - start_clock);
+}
+
 static int power_pmu_prepare_cpu(unsigned int cpu)
 {
 	struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);