From: Rob Herring <robh@kernel.org>
To: Will Deacon <will@kernel.org>, Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Raphael Gault <raphael.gault@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH 3/5] arm64: pmu: Add function implementation to update event index in userpage
Date: Tue, 7 Jul 2020 14:53:31 -0600 [thread overview]
Message-ID: <20200707205333.624938-4-robh@kernel.org> (raw)
In-Reply-To: <20200707205333.624938-1-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 d4b4fe69fe2c..6c12a6ad36f5 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -795,6 +795,22 @@ 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.
*/
@@ -891,6 +907,9 @@ 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)) {
@@ -1068,6 +1087,8 @@ 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
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next prev parent reply other threads:[~2020-07-07 20:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 20:53 [PATCH 0/5] arm64: Enable access to pmu registers by user-space Rob Herring
2020-07-07 20:53 ` [PATCH 1/5] perf: arm64: Add tests to check userspace access to hardware counters Rob Herring
2020-07-07 20:53 ` [PATCH 2/5] arm64: pmu: Add hook to handle pmu-related undefined instructions Rob Herring
2020-07-07 20:53 ` Rob Herring [this message]
2020-07-07 20:53 ` [PATCH 4/5] arm64: perf: Enable pmu counter direct access for perf event on armv8 Rob Herring
2020-07-07 20:53 ` [PATCH 5/5] Documentation: arm64: Document PMU counters access from userspace Rob Herring
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