perf/x86/intel: Honour the CPUID for number of fixed counters in hypervisors

perf doesn't seem to honour the number of fixed counters specified by CPUID
leaf 0xa. It always assumes that Intel CPUs have at least 3 fixed counters.

So if some of the fixed counters are masked out by the hypervisor, it still
tries to check/set them.

This patch makes perf behave nicer when the kernel is running under a
hypervisor that doesn't expose all the counters.

This patch contains some ideas from Matt Wilson.

Signed-off-by: Imre Palik <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
Cc: Alexander Kozyrev <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Artyom Kuanbekov <[email protected]>
Cc: David Carrillo-Cisneros <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Wilson <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index eab0915f5995..a74a2dbc0180 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3607,10 +3607,14 @@ __init int intel_pmu_init(void)
 
 	/*
 	 * Quirk: v2 perfmon does not report fixed-purpose events, so
-	 * assume at least 3 events:
+	 * assume at least 3 events, when not running in a hypervisor:
 	 */
-	if (version > 1)
-		x86_pmu.num_counters_fixed = max((int)edx.split.num_counters_fixed, 3);
+	if (version > 1) {
+		int assume = 3 * !boot_cpu_has(X86_FEATURE_HYPERVISOR);
+
+		x86_pmu.num_counters_fixed =
+			max((int)edx.split.num_counters_fixed, assume);
+	}
 
 	if (boot_cpu_has(X86_FEATURE_PDCM)) {
 		u64 capabilities;