[PATCH 26/31] perf, x86: Support for printing PMU state on spurious PMIs

[Andi Kleen <andi@firstfloor.org>]

From: Andi Kleen <ak@linux.intel.com>

I had some problems with spurious PMIs, so print the PMU state
on a spurious one. This will not interact well with other NMI users.
Disabled by default, has to be explicitely enabled through sysfs.

Optional, but useful for debugging.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index be0d3c8..baf78e0 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -12,6 +12,7 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/export.h>
+#include <linux/moduleparam.h>
 
 #include <asm/cpufeature.h>
 #include <asm/hardirq.h>
@@ -19,6 +20,9 @@
 
 #include "perf_event.h"
 
+static bool print_spurious_pmi __read_mostly;
+module_param(print_spurious_pmi, bool, 0644);
+
 /*
  * Intel PerfMon, used on Core and later.
  */
@@ -1237,6 +1241,10 @@ again:
 		goto again;
 
 done:
+	if (!handled && print_spurious_pmi) {
+		pr_debug("Spurious PMI\n");
+		perf_event_print_debug();
+	}
 	intel_pmu_enable_all(0);
 	return handled;
 }
-- 
1.7.7.6