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>, Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
honnappa.nagarahalli@arm.com, Zachary.Leaf@arm.com,
Raphael Gault <raphael.gault@arm.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Namhyung Kim <namhyung@kernel.org>,
Itaru Kitayama <itaru.kitayama@gmail.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v7 2/9] arm64: pmu: Add function implementation to update event index in userpage
Date: Mon, 19 Apr 2021 22:15:04 -0500 [thread overview]
Message-ID: <20210420031511.2348977-3-robh@kernel.org> (raw)
In-Reply-To: <20210420031511.2348977-1-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>
---
v7:
- Add define ARMV8_IDX_CYCLE_COUNTER_USER for userspace index
of cycle counter
---
arch/arm64/kernel/perf_event.c | 20 +++++++++++++++++++-
include/linux/perf/arm_pmu.h | 2 ++
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 4658fcf88c2b..40cf59455ce8 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -332,7 +332,7 @@ static const struct attribute_group armv8_pmuv3_caps_attr_group = {
*/
#define ARMV8_IDX_CYCLE_COUNTER 0
#define ARMV8_IDX_COUNTER0 1
-
+#define ARMV8_IDX_CYCLE_COUNTER_USER 32
/*
* We unconditionally enable ARMv8.5-PMU long event counter support
@@ -871,6 +871,22 @@ 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 ARMV8_IDX_CYCLE_COUNTER_USER;
+
+ return event->hw.idx;
+}
+
/*
* Add an event filter to a given event.
*/
@@ -1098,6 +1114,8 @@ 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 505480217cf1..d29aa981d989 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
--
2.27.0
next prev parent reply other threads:[~2021-04-20 3:15 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 3:15 [PATCH v7 0/9] arm64 userspace counter access support Rob Herring
2021-04-20 3:15 ` [PATCH v7 1/9] arm64: Restrict undef hook for cpufeature registers Rob Herring
2021-04-20 3:15 ` Rob Herring [this message]
2021-04-20 3:15 ` [PATCH v7 3/9] arm64: perf: Enable PMU counter direct access for perf event Rob Herring
2021-04-20 3:15 ` [PATCH v7 4/9] drivers/perf: arm_pmu: Export the per_cpu cpu_armpmu Rob Herring
2021-04-20 3:15 ` [PATCH v7 5/9] arm64: perf: Add userspace counter access disable switch Rob Herring
2021-04-20 3:15 ` [PATCH v7 6/9] libperf: Add arm64 support to perf_mmap__read_self() Rob Herring
2021-04-20 3:15 ` [PATCH v7 7/9] perf: arm64: Add test for userspace counter access on heterogeneous systems Rob Herring
2021-04-30 16:46 ` Masayoshi Mizuma
2021-04-30 18:17 ` Rob Herring
2021-04-30 18:20 ` Rob Herring
2021-04-30 20:16 ` Masayoshi Mizuma
2021-05-13 9:05 ` nakamura.shun
2021-05-13 12:37 ` Rob Herring
2021-04-20 3:15 ` [PATCH v7 8/9] perf: arm64: Add tests for 32-bit and 64-bit counter size userspace access Rob Herring
2021-04-20 3:15 ` [PATCH v7 9/9] Documentation: arm64: Document PMU counters access from userspace Rob Herring
2021-04-30 18:59 ` [PATCH v7 0/9] arm64 userspace counter access support Arnaldo Carvalho de Melo
2021-05-03 14:56 ` Rob Herring
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