powerpc/perf: Don't enable if we have zero events

In power_pmu_enable() we still enable the PMU even if we have zero
events. This should have no effect but doesn't make much sense. Instead
just return after telling the hypervisor that we are not using the PMCs.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
CC: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 1bb26d586e3c..c91dc43e04de 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -926,6 +926,11 @@ static void power_pmu_enable(struct pmu *pmu)
         if (!cpuhw->disabled)
                 goto out;
 
+        if (cpuhw->n_events == 0) {
+                ppc_set_pmu_inuse(0);
+                goto out;
+        }
+
         cpuhw->disabled = 0;
 
         /*
@@ -937,8 +942,6 @@ static void power_pmu_enable(struct pmu *pmu)
         if (!cpuhw->n_added) {
                 mtspr(SPRN_MMCRA, cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE);
                 mtspr(SPRN_MMCR1, cpuhw->mmcr[1]);
-                if (cpuhw->n_events == 0)
-                        ppc_set_pmu_inuse(0);
                 goto out_enable;
         }