[tip:perfcounters/core] perf_counter: fix fixed-purpose counter support on v2 Intel-PERFMON

[tip-bot for Ingo Molnar]

Commit-ID:  066d7dea32c9bffe6decc0abe465627656cdd84e
Gitweb:     http://git.kernel.org/tip/066d7dea32c9bffe6decc0abe465627656cdd84e
Author:     Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Mon, 4 May 2009 19:04:09 +0200
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Mon, 4 May 2009 20:17:31 +0200

perf_counter: fix fixed-purpose counter support on v2 Intel-PERFMON

Fixed-purpose counters stopped working in a simple 'perf stat ls' run:

   <not counted>  cache references
   <not counted>  cache misses

Due to:

  ef7b3e0: perf_counter, x86: remove vendor check in fixed_mode_idx()

Which made x86_pmu.num_counters_fixed matter: if it's nonzero, the
fixed-purpose counters are utilized.

But on v2 perfmon this field is not set (despite there being
fixed-purpose PMCs). So add a quirk to set the number of fixed-purpose
counters to at least three.

[ Impact: add quirk for three fixed-purpose counters on certain Intel CPUs ]

Cc: Robert Richter <robert.richter@xxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <1241002046-8832-28-git-send-email-robert.richter@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 arch/x86/kernel/cpu/perf_counter.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 196b58f..a6878b0 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -962,7 +962,13 @@ static int intel_pmu_init(void)
 	x86_pmu = intel_pmu;
 	x86_pmu.version = version;
 	x86_pmu.num_counters = eax.split.num_counters;
-	x86_pmu.num_counters_fixed = edx.split.num_counters_fixed;
+
+	/*
+	 * Quirk: v2 perfmon does not report fixed-purpose counters, so
+	 * assume at least 3 counters:
+	 */
+	x86_pmu.num_counters_fixed = max((int)edx.split.num_counters_fixed, 3);
+
 	x86_pmu.counter_bits = eax.split.bit_width;
 	x86_pmu.counter_mask = (1ULL << eax.split.bit_width) - 1;
 
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