linux-kernel - [PATCH 1/2] perf_events: check for filters on fixed counter events

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Date:	Tue,  6 Oct 2009 16:42:08 +0200
From:	Stephane Eranian <eranian@...glemail.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, paulus@...ba.org, a.p.zijlstra@...llo.nl,
	perfmon2-devel@...ts.sf.net, Stephane Eranian <eranian@...il.com>
Subject: [PATCH 1/2] perf_events: check for filters on fixed counter events

	Intel fixed counters do not support all the filters
	possible with a generic counter. Thus, if a  fixed counter
	event is passed but with certain filters set, then the
	fixed_mode_idx() function must fail and the event must be
	measured in a generic counter instead.

	Reject filters are: inv, edge, cnt-mask

	Signed-off-by: Stephane Eranian <eranian@...il.com>
---
 arch/x86/include/asm/perf_event.h |   11 +++++++++++
 arch/x86/kernel/cpu/perf_event.c  |    6 ++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index ad7ce3f..719273b 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -28,6 +28,17 @@
  */
 #define ARCH_PERFMON_EVENT_MASK				    0xffff
 
+/*
+ * filter mask to validate fixed counter events.
+ * the following filters disqualify for fixed counters:
+ *  - inv
+ *  - edge
+ *  - cnt-mask
+ *  The other filters are supported by fixed counters.
+ *  The any-thread option is supported starting with v3.
+ */
+#define ARCH_PERFMON_EVENT_FILTER_MASK			0xff840000
+
 #define ARCH_PERFMON_UNHALTED_CORE_CYCLES_SEL		      0x3c
 #define ARCH_PERFMON_UNHALTED_CORE_CYCLES_UMASK		(0x00 << 8)
 #define ARCH_PERFMON_UNHALTED_CORE_CYCLES_INDEX 		 0
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index b5801c3..1d16bd6 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1349,6 +1349,12 @@ fixed_mode_idx(struct perf_event *event, struct hw_perf_event *hwc)
 	if (!x86_pmu.num_events_fixed)
 		return -1;
 
+	/*
+	 * fixed counters do not take all possible filters
+	 */
+	if (hwc->config & ARCH_PERFMON_EVENT_FILTER_MASK)
+		return -1;
+
 	if (unlikely(hw_event == x86_pmu.event_map(PERF_COUNT_HW_INSTRUCTIONS)))
 		return X86_PMC_IDX_FIXED_INSTRUCTIONS;
 	if (unlikely(hw_event == x86_pmu.event_map(PERF_COUNT_HW_CPU_CYCLES)))
-- 
1.5.4.3

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