Commit dbc33f70 authored Sep 09, 2013 by Stephane Eranian Committed by Ingo Molnar Sep 12, 2013

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>

parent 878b5a6e

arch/x86/kernel/cpu/perf_event_intel_uncore.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -2808,7 +2808,7 @@ uncore_get_event_constraint(struct intel_uncore_box box, struct perf_event eve
		return c;
		}

		if (event->hw.config == ~0ULL)
		if (event->attr.config == UNCORE_FIXED_EVENT)
		return &constraint_fixed;

		if (type->constraints) {
		@@ -3112,7 +3112,9 @@ static int uncore_pmu_event_init(struct perf_event *event)
		*/
		if (pmu->type->single_fixed && pmu->pmu_idx > 0)
		return -EINVAL;
		hwc->config = ~0ULL;

		/* fixed counters have event field hardcoded to zero */
		hwc->config = 0ULL;
		} else {
		hwc->config = event->attr.config & pmu->type->event_mask;
		if (pmu->type->ops->hw_config) {