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Commit dbc33f7016747bfce64f3d1e3af63f1251fcbf85

Authored by Stephane Eranian
Committed by Ingo Molnar
1 parent 878b5a6efd
Exists in smarc-imx_3.14.28_1.0.0_ga and in 1 other branch imx_3.14.28_1.0.0_ga

perf/x86: Fix uncore PCI fixed counter handling 

There was a bug in the handling of SNB-EP/IVB-EP uncore PCI
fixed counters, e.g., IMC.

It would cause erratic values to be returned for the IMC
clockticks event. This was due to a bogus hwc->config value
which was then written to PCI config space.

The erratic values can be seen via:

  $ perf stat -a -C 0 -e uncore_imc_0/clockticks/ -I 1000 sleep 10

The fixed counter has most fields marked as reserved with
hw reset values of 0. Yet the kernel was defaulting to a
hwc->config = ~0 and that was causing the issues.

This patch sets the hwc->config values for fixed uncore event
to 0. Now, the values of IMC clockticks is correct.

Signed-off-by: Stephane Eranian <eranian@google.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: peterz@infradead.org
Cc: zheng.z.yan@intel.com
Link: http://lkml.kernel.org/r/20130909195350.GA17643@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Showing 1 changed file with 4 additions and 2 deletions Side-by-side Diff

arch/x86/kernel/cpu/perf_event_intel_uncore.c
Diff comments   View file @ dbc33f7
... ... @@ -2808,7 +2808,7 @@
2808 2808 return c;
2809 2809 }
2810 2810  
2811   - if (event->hw.config == ~0ULL)
  2811 + if (event->attr.config == UNCORE_FIXED_EVENT)
2812 2812 return &constraint_fixed;
2813 2813  
2814 2814 if (type->constraints) {
... ... @@ -3112,7 +3112,9 @@
3112 3112 */
3113 3113 if (pmu->type->single_fixed && pmu->pmu_idx > 0)
3114 3114 return -EINVAL;
3115   - hwc->config = ~0ULL;
  3115 +
  3116 + /* fixed counters have event field hardcoded to zero */
  3117 + hwc->config = 0ULL;
3116 3118 } else {
3117 3119 hwc->config = event->attr.config & pmu->type->event_mask;
3118 3120 if (pmu->type->ops->hw_config) {