[PATCH V2 2/7] arm64/perf: Update struct arm_pmu for BRBE

Anshuman Khandual
2022-09-08T05:11:15Z

Although BRBE is an armv8 speciifc HW feature, abstracting out its various
function callbacks at the struct arm_pmu level is preferred, as it cleaner
, easier to follow and maintain.

Besides some helpers i.e brbe_supported(), brbe_probe() and brbe_reset()
might not fit seamlessly, when tried to be embedded via existing arm_pmu
helpers in the armv8 implementation.

Updates the struct arm_pmu to include all required helpers that will drive
BRBE functionality for a given PMU implementation. These are the following.

- brbe_filter : Convert perf event filters into BRBE HW filters
- brbe_probe : Probe BRBE HW and capture its attributes
- brbe_enable : Enable BRBE HW with a given config
- brbe_disable : Disable BRBE HW
- brbe_read : Read BRBE buffer for captured branch records
- brbe_reset : Reset BRBE buffer
- brbe_supported: Whether BRBE is supported or not

A BRBE driver implementation needs to provide these functionalities.

Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-perf-users@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
arch/arm64/kernel/perf_event.c | 36 ++++++++++++++++++++++++++++++++++
include/linux/perf/arm_pmu.h | 21 ++++++++++++++++++++
2 files changed, 57 insertions(+)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index cb69ff1e6138..e7013699171f 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -1025,6 +1025,35 @@ static int armv8pmu_filter_match(struct perf_event *event)
return evtype != ARMV8_PMUV3_PERFCTR_CHAIN;
}

+static void armv8pmu_brbe_filter(struct pmu_hw_events *hw_event, struct perf_event *event)
+{
+}
+
+static void armv8pmu_brbe_enable(struct pmu_hw_events *hw_event)
+{
+}
+
+static void armv8pmu_brbe_disable(struct pmu_hw_events *hw_event)
+{
+}
+
+static void armv8pmu_brbe_read(struct pmu_hw_events *hw_event, struct perf_event *event)
+{
+}
+
+static void armv8pmu_brbe_probe(struct pmu_hw_events *hw_event)
+{
+}
+
+static void armv8pmu_brbe_reset(struct pmu_hw_events *hw_event)
+{
+}
+
+static bool armv8pmu_brbe_supported(struct perf_event *event)
+{
+ return false;
+}
+
static void armv8pmu_reset(void *info)
{
struct arm_pmu *cpu_pmu = (struct arm_pmu *)info;
@@ -1257,6 +1286,13 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,

cpu_pmu->pmu.event_idx = armv8pmu_user_event_idx;

+ cpu_pmu->brbe_filter = armv8pmu_brbe_filter;
+ cpu_pmu->brbe_enable = armv8pmu_brbe_enable;
+ cpu_pmu->brbe_disable = armv8pmu_brbe_disable;
+ cpu_pmu->brbe_read = armv8pmu_brbe_read;
+ cpu_pmu->brbe_probe = armv8pmu_brbe_probe;
+ cpu_pmu->brbe_reset = armv8pmu_brbe_reset;
+ cpu_pmu->brbe_supported = armv8pmu_brbe_supported;
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 0407a38b470a..3d427ac0ca45 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -100,6 +100,27 @@ struct arm_pmu {
void (*reset)(void *);
int (*map_event)(struct perf_event *event);
int (*filter_match)(struct perf_event *event);
+
+ /* Convert perf event filters into BRBE HW filters */
+ void (*brbe_filter)(struct pmu_hw_events *hw_events, struct perf_event *event);
+
+ /* Probe BRBE HW and capture its attributes */
+ void (*brbe_probe)(struct pmu_hw_events *hw_events);
+
+ /* Enable BRBE HW with a given config */
+ void (*brbe_enable)(struct pmu_hw_events *hw_events);
+
+ /* Disable BRBE HW */
+ void (*brbe_disable)(struct pmu_hw_events *hw_events);
+
+ /* Process BRBE buffer for captured branch records */
+ void (*brbe_read)(struct pmu_hw_events *hw_events, struct perf_event *event);
+
+ /* Reset BRBE buffer */
+ void (*brbe_reset)(struct pmu_hw_events *hw_events);
+
+ /* Check whether BRBE is supported */
+ bool (*brbe_supported)(struct perf_event *event);
int num_events;
bool secure_access; /* 32-bit ARM only */
#define ARMV8_PMUV3_MAX_COMMON_EVENTS 0x40
--
2.25.1