powerpc/64s/perf: add power_pmu_running to query whether perf is bein…

…g used

Interrupt handling code would like to know whether perf is enabled, to
know whether it should enable MSR[EE] to improve PMI coverage.

Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

arch/powerpc/include/asm/hw_irq.h

@@ -306,6 +306,8 @@ static inline bool lazy_irq_pending_nocheck(void)
 	return __lazy_irq_pending(local_paca->irq_happened);
 }
 
+bool power_pmu_running(void);
+
 /*
  * This is called by asynchronous interrupts to conditionally
  * re-enable hard interrupts after having cleared the source

arch/powerpc/perf/core-book3s.c

@@ -2389,6 +2389,19 @@ static void perf_event_interrupt(struct pt_regs *regs)
 	perf_sample_event_took(sched_clock() - start_clock);
 }
 
+bool power_pmu_running(void)
+{
+	struct cpu_hw_events *cpuhw;
+
+	/* Could this simply test local_paca->pmcregs_in_use? */
+
+	if (!ppmu)
+		return false;
+
+	cpuhw = this_cpu_ptr(&cpu_hw_events);
+	return cpuhw->n_events;
+}
+
 static int power_pmu_prepare_cpu(unsigned int cpu)
 {
 	struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);