linux-kernel - [tip:perf/urgent] perf/x86: Fix uncore PCI fixed counter handling

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Message-ID: <tip-dbc33f7016747bfce64f3d1e3af63f1251fcbf85@git.kernel.org>
Date:	Thu, 12 Sep 2013 04:11:48 -0700
From:	tip-bot for Stephane Eranian <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com, hpa@...or.com,
	mingo@...nel.org, ak@...ux.intel.com, tglx@...utronix.de
Subject: [tip:perf/urgent] perf/x86: Fix uncore PCI fixed counter handling

Commit-ID:  dbc33f7016747bfce64f3d1e3af63f1251fcbf85
Gitweb:     http://git.kernel.org/tip/dbc33f7016747bfce64f3d1e3af63f1251fcbf85
Author:     Stephane Eranian <eranian@...gle.com>
AuthorDate: Mon, 9 Sep 2013 12:53:50 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 12 Sep 2013 08:42:37 +0200

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@...gle.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Cc: peterz@...radead.org
Cc: zheng.z.yan@...el.com
Link: http://lkml.kernel.org/r/20130909195350.GA17643@google.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/perf_event_intel_uncore.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index fd8011e..8ed4458 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -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) {
--
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