From: Rob Herring <robh@kernel.org>
To: Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Raphael Gault <raphael.gault@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Ian Rogers <irogers@google.com>,
honnappa.nagarahalli@arm.com,
Itaru Kitayama <itaru.kitayama@gmail.com>
Subject: [PATCH v4 1/9] arm64: pmu: Add function implementation to update event index in userpage
Date: Thu, 1 Oct 2020 09:01:08 -0500 [thread overview]
Message-ID: <20201001140116.651970-2-robh@kernel.org> (raw)
In-Reply-To: <20201001140116.651970-1-robh@kernel.org>
From: Raphael Gault <raphael.gault@arm.com>
In order to be able to access the counter directly for userspace,
we need to provide the index of the counter using the userpage.
We thus need to override the event_idx function to retrieve and
convert the perf_event index to armv8 hardware index.
Since the arm_pmu driver can be used by any implementation, even
if not armv8, two components play a role into making sure the
behaviour is correct and consistent with the PMU capabilities:
* the ARMPMU_EL0_RD_CNTR flag which denotes the capability to access
counter from userspace.
* the event_idx call back, which is implemented and initialized by
the PMU implementation: if no callback is provided, the default
behaviour applies, returning 0 as index value.
Signed-off-by: Raphael Gault <raphael.gault@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
---
arch/arm64/kernel/perf_event.c | 21 +++++++++++++++++++++
include/linux/perf/arm_pmu.h | 2 ++
2 files changed, 23 insertions(+)
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 462f9a9cc44b..e14f360a7883 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -818,6 +818,22 @@ static void armv8pmu_clear_event_idx(struct pmu_hw_events *cpuc,
clear_bit(idx - 1, cpuc->used_mask);
}
+static int armv8pmu_access_event_idx(struct perf_event *event)
+{
+ if (!(event->hw.flags & ARMPMU_EL0_RD_CNTR))
+ return 0;
+
+ /*
+ * We remap the cycle counter index to 32 to
+ * match the offset applied to the rest of
+ * the counter indices.
+ */
+ if (event->hw.idx == ARMV8_IDX_CYCLE_COUNTER)
+ return 32;
+
+ return event->hw.idx;
+}
+
/*
* Add an event filter to a given event.
*/
@@ -914,6 +930,9 @@ static int __armv8_pmuv3_map_event(struct perf_event *event,
if (armv8pmu_event_is_64bit(event))
event->hw.flags |= ARMPMU_EVT_64BIT;
+ if (!armv8pmu_event_is_chained(event))
+ event->hw.flags |= ARMPMU_EL0_RD_CNTR;
+
/* Only expose micro/arch events supported by this PMU */
if ((hw_event_id > 0) && (hw_event_id < ARMV8_PMUV3_MAX_COMMON_EVENTS)
&& test_bit(hw_event_id, armpmu->pmceid_bitmap)) {
@@ -1038,6 +1057,8 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
cpu_pmu->set_event_filter = armv8pmu_set_event_filter;
cpu_pmu->filter_match = armv8pmu_filter_match;
+ cpu_pmu->pmu.event_idx = armv8pmu_access_event_idx;
+
cpu_pmu->name = name;
cpu_pmu->map_event = map_event;
cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_EVENTS] = events ?
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index 5b616dde9a4c..74fbbbd29dc7 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -26,6 +26,8 @@
*/
/* Event uses a 64bit counter */
#define ARMPMU_EVT_64BIT 1
+/* Allow access to hardware counter from userspace */
+#define ARMPMU_EL0_RD_CNTR 2
#define HW_OP_UNSUPPORTED 0xFFFF
#define C(_x) PERF_COUNT_HW_CACHE_##_x
--
2.25.1
next prev parent reply other threads:[~2020-10-01 14:02 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 14:01 [PATCH v4 0/9] libperf and arm64 userspace counter access support Rob Herring
2020-10-01 14:01 ` Rob Herring [this message]
2020-10-01 14:01 ` [PATCH v4 2/9] arm64: perf: Enable pmu counter direct access for perf event on armv8 Rob Herring
2020-11-13 18:06 ` Mark Rutland
2020-11-19 18:35 ` Rob Herring
2020-11-19 19:15 ` Will Deacon
2020-11-20 20:03 ` Rob Herring
2020-11-20 22:08 ` Rob Herring
2020-12-02 14:57 ` Rob Herring
2021-01-07 0:17 ` Rob Herring
2020-10-01 14:01 ` [PATCH v4 3/9] tools/include: Add an initial math64.h Rob Herring
2020-10-01 14:01 ` [PATCH v4 4/9] libperf: Add libperf_evsel__mmap() Rob Herring
2020-10-14 11:05 ` Jiri Olsa
2020-10-16 21:39 ` Rob Herring
2020-10-19 20:15 ` Jiri Olsa
2020-10-20 14:38 ` Rob Herring
2020-10-20 15:35 ` Jiri Olsa
2020-10-20 17:11 ` Rob Herring
2020-10-21 11:24 ` Jiri Olsa
2020-11-05 16:19 ` Rob Herring
2020-11-05 22:41 ` Jiri Olsa
2020-11-06 21:56 ` Rob Herring
2020-11-11 12:00 ` Jiri Olsa
2020-11-11 14:50 ` Rob Herring
2020-10-01 14:01 ` [PATCH v4 5/9] libperf: tests: Add support for verbose printing Rob Herring
2020-10-01 14:01 ` [PATCH v4 6/9] libperf: Add support for user space counter access Rob Herring
2020-10-01 14:01 ` [PATCH v4 7/9] libperf: Add arm64 support to perf_mmap__read_self() Rob Herring
2020-10-01 14:01 ` [PATCH v4 8/9] perf: arm64: Add test for userspace counter access on heterogeneous systems Rob Herring
2020-10-01 14:01 ` [PATCH v4 9/9] Documentation: arm64: Document PMU counters access from userspace Rob Herring
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