At present ARMv8 event counters are limited to 32-bits, though by
using the CHAIN event it's possible to combine adjacent counters to
achieve 64-bits. The perf config1:0 bit can be set to use such a
configuration.
With the introduction of ARMv8.5-PMU support, all event counters can
now be used as 64-bit counters.
Let's enable 64-bit event counters where support exists. Unless the
user sets config1:0 we will adjust the counter value such that it
overflows upon 32-bit overflow. This follows the same behaviour as
the cycle counter which has always been (and remains) 64-bits.
Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
arch/arm64/include/asm/perf_event.h | 3 +-
arch/arm64/kernel/perf_event.c | 86 +++++++++++++++++++++++------
include/linux/perf/arm_pmu.h | 1 +
3 files changed, 72 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h
index 2bdbc79bbd01..e7765b62c712 100644
--- a/arch/arm64/include/asm/perf_event.h
+++ b/arch/arm64/include/asm/perf_event.h
@@ -176,9 +176,10 @@
#define ARMV8_PMU_PMCR_X (1 << 4) /* Export to ETM */
#define ARMV8_PMU_PMCR_DP (1 << 5) /* Disable CCNT if non-invasive debug*/
#define ARMV8_PMU_PMCR_LC (1 << 6) /* Overflow on 64 bit cycle counter */
+#define ARMV8_PMU_PMCR_LP (1 << 7) /* Long event counter enable */
#define ARMV8_PMU_PMCR_N_SHIFT 11 /* Number of counters supported */
#define ARMV8_PMU_PMCR_N_MASK 0x1f
-#define ARMV8_PMU_PMCR_MASK 0x7f /* Mask for writable bits */
+#define ARMV8_PMU_PMCR_MASK 0xff /* Mask for writable bits */
/*
* PMOVSR: counters overflow flag status reg
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index e40b65645c86..4e27f90bb89e 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -285,6 +285,17 @@ static struct attribute_group armv8_pmuv3_format_attr_group = {
#define ARMV8_IDX_COUNTER_LAST(cpu_pmu) \
(ARMV8_IDX_CYCLE_COUNTER + cpu_pmu->num_events - 1)
+
+/*
+ * We unconditionally enable ARMv8.5-PMU long event counter support
+ * (64-bit events) where supported. Indicate if this arm_pmu has long
+ * event counter support.
+ */
+static bool armv8pmu_has_long_event(struct arm_pmu *cpu_pmu)
+{
+ return (cpu_pmu->pmuver > ID_DFR0_EL1_PMUVER_8_4);
+}
+
/*
* We must chain two programmable counters for 64 bit events,
* except when we have allocated the 64bit cycle counter (for CPU
@@ -294,9 +305,11 @@ static struct attribute_group armv8_pmuv3_format_attr_group = {
static inline bool armv8pmu_event_is_chained(struct perf_event *event)
{
int idx = event->hw.idx;
+ struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
return !WARN_ON(idx < 0) &&
armv8pmu_event_is_64bit(event) &&
+ !armv8pmu_has_long_event(cpu_pmu) &&
(idx != ARMV8_IDX_CYCLE_COUNTER);
}
@@ -345,7 +358,7 @@ static inline void armv8pmu_select_counter(int idx)
isb();
}
-static inline u32 armv8pmu_read_evcntr(int idx)
+static inline u64 armv8pmu_read_evcntr(int idx)
{
armv8pmu_select_counter(idx);
return read_sysreg(pmxevcntr_el0);
@@ -362,6 +375,44 @@ static inline u64 armv8pmu_read_hw_counter(struct perf_event *event)
return val;
}
+/*
+ * The cycle counter is always a 64-bit counter. When ARMV8_PMU_PMCR_LP
+ * is set the event counters also become 64-bit counters. Unless the
+ * user has requested a long counter (attr.config1) then we want to
+ * interrupt upon 32-bit overflow - we achieve this by applying a bias.
+ */
+static bool armv8pmu_event_needs_bias(struct perf_event *event)
+{
+ struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
+ struct hw_perf_event *hwc = &event->hw;
+ int idx = hwc->idx;
+
+ if (armv8pmu_event_is_64bit(event))
+ return false;
+
+ if (armv8pmu_has_long_event(cpu_pmu) ||
+ idx == ARMV8_IDX_CYCLE_COUNTER)
+ return true;
+
+ return false;
+}
+
+static u64 armv8pmu_bias_long_counter(struct perf_event *event, u64 value)
+{
+ if (armv8pmu_event_needs_bias(event))
+ value |= GENMASK(63, 32);
+
+ return value;
+}
+
+static u64 armv8pmu_unbias_long_counter(struct perf_event *event, u64 value)
+{
+ if (armv8pmu_event_needs_bias(event))
+ value &= ~GENMASK(63, 32);
+
+ return value;
+}
+
static u64 armv8pmu_read_counter(struct perf_event *event)
{
struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
@@ -377,10 +428,10 @@ static u64 armv8pmu_read_counter(struct perf_event *event)
else
value = armv8pmu_read_hw_counter(event);
- return value;
+ return armv8pmu_unbias_long_counter(event, value);
}
-static inline void armv8pmu_write_evcntr(int idx, u32 value)
+static inline void armv8pmu_write_evcntr(int idx, u64 value)
{
armv8pmu_select_counter(idx);
write_sysreg(value, pmxevcntr_el0);
@@ -405,20 +456,14 @@ static void armv8pmu_write_counter(struct perf_event *event, u64 value)
struct hw_perf_event *hwc = &event->hw;
int idx = hwc->idx;
+ value = armv8pmu_bias_long_counter(event, value);
+
if (!armv8pmu_counter_valid(cpu_pmu, idx))
pr_err("CPU%u writing wrong counter %d\n",
smp_processor_id(), idx);
- else if (idx == ARMV8_IDX_CYCLE_COUNTER) {
- /*
- * The cycles counter is really a 64-bit counter.
- * When treating it as a 32-bit counter, we only count
- * the lower 32 bits, and set the upper 32-bits so that
- * we get an interrupt upon 32-bit overflow.
- */
- if (!armv8pmu_event_is_64bit(event))
- value |= 0xffffffff00000000ULL;
+ else if (idx == ARMV8_IDX_CYCLE_COUNTER)
write_sysreg(value, pmccntr_el0);
- } else
+ else
armv8pmu_write_hw_counter(event, value);
}
@@ -743,7 +788,8 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
/*
* Otherwise use events counters
*/
- if (armv8pmu_event_is_64bit(event))
+ if (armv8pmu_event_is_64bit(event) &&
+ !armv8pmu_has_long_event(cpu_pmu))
return armv8pmu_get_chain_idx(cpuc, cpu_pmu);
else
return armv8pmu_get_single_idx(cpuc, cpu_pmu);
@@ -815,7 +861,7 @@ static int armv8pmu_filter_match(struct perf_event *event)
static void armv8pmu_reset(void *info)
{
struct arm_pmu *cpu_pmu = (struct arm_pmu *)info;
- u32 idx, nb_cnt = cpu_pmu->num_events;
+ u32 idx, pmcr, nb_cnt = cpu_pmu->num_events;
/* The counter and interrupt enable registers are unknown at reset. */
for (idx = ARMV8_IDX_CYCLE_COUNTER; idx < nb_cnt; ++idx) {
@@ -830,8 +876,13 @@ static void armv8pmu_reset(void *info)
* Initialize & Reset PMNC. Request overflow interrupt for
* 64 bit cycle counter but cheat in armv8pmu_write_counter().
*/
- armv8pmu_pmcr_write(ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C |
- ARMV8_PMU_PMCR_LC);
+ pmcr = ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C | ARMV8_PMU_PMCR_LC;
+
+ /* Enable long event counter support where available */
+ if (armv8pmu_has_long_event(cpu_pmu))
+ pmcr |= ARMV8_PMU_PMCR_LP;
+
+ armv8pmu_pmcr_write(pmcr);
}
static int __armv8_pmuv3_map_event(struct perf_event *event,
@@ -914,6 +965,7 @@ static void __armv8pmu_probe_pmu(void *info)
if (pmuver == 0xf || pmuver == 0)
return;
+ cpu_pmu->pmuver = pmuver;
probe->present = true;
/* Read the nb of CNTx counters supported from PMNC */
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index 71f525a35ac2..5b616dde9a4c 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -80,6 +80,7 @@ struct arm_pmu {
struct pmu pmu;
cpumask_t supported_cpus;
char *name;
+ int pmuver;
irqreturn_t (*handle_irq)(struct arm_pmu *pmu);
void (*enable)(struct perf_event *event);
void (*disable)(struct perf_event *event);
--
2.21.0
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
