[RFC PATCH 4/6] riscv: perf: Add raw event support

From: Zong Li
Date: Sun Jun 28 2020 - 23:19:35 EST

Add support for raw events and hardware cache events. Currently, we set
the events by writing the mhpmeventN CSRs, it would raise an illegal
instruction exception and trap into m-mode to emulate event selector
CSRs access. It doesn't make sense because we shouldn't write the
m-mode CSRs in s-mode, it would be better that set events through SBI
call or the shadow CSRs of s-mode. We would change it later.

Signed-off-by: Zong Li <zong.li@xxxxxxxxxx>
---
arch/riscv/include/asm/perf_event.h | 65 ++++++---
arch/riscv/kernel/perf_event.c | 204 +++++++++++++++++++++++-----
2 files changed, 215 insertions(+), 54 deletions(-)

diff --git a/arch/riscv/include/asm/perf_event.h b/arch/riscv/include/asm/perf_event.h
index 062efd3a1d5d..41d515a1f331 100644
--- a/arch/riscv/include/asm/perf_event.h
+++ b/arch/riscv/include/asm/perf_event.h
@@ -14,39 +14,64 @@

#ifdef CONFIG_RISCV_BASE_PMU
#define RISCV_BASE_COUNTERS 2
+#define RISCV_EVENT_COUNTERS 29
+#define RISCV_TOTAL_COUNTERS (RISCV_BASE_COUNTERS + RISCV_EVENT_COUNTERS)

/*
- * The RISCV_MAX_COUNTERS parameter should be specified.
- */
-
-#define RISCV_MAX_COUNTERS 2
-
-/*
- * These are the indexes of bits in counteren register *minus* 1,
- * except for cycle. It would be coherent if it can directly mapped
- * to counteren bit definition, but there is a *time* register at
- * counteren[1]. Per-cpu structure is scarce resource here.
- *
* According to the spec, an implementation can support counter up to
* mhpmcounter31, but many high-end processors has at most 6 general
* PMCs, we give the definition to MHPMCOUNTER8 here.
*/
-#define RISCV_PMU_CYCLE 0
-#define RISCV_PMU_INSTRET 1
-#define RISCV_PMU_MHPMCOUNTER3 2
-#define RISCV_PMU_MHPMCOUNTER4 3
-#define RISCV_PMU_MHPMCOUNTER5 4
-#define RISCV_PMU_MHPMCOUNTER6 5
-#define RISCV_PMU_MHPMCOUNTER7 6
-#define RISCV_PMU_MHPMCOUNTER8 7
+#define RISCV_PMU_CYCLE 0
+#define RISCV_PMU_INSTRET 2
+#define RISCV_PMU_HPMCOUNTER3 3
+#define RISCV_PMU_HPMCOUNTER4 4
+#define RISCV_PMU_HPMCOUNTER5 5
+#define RISCV_PMU_HPMCOUNTER6 6
+#define RISCV_PMU_HPMCOUNTER7 7
+#define RISCV_PMU_HPMCOUNTER8 8
+
+#define RISCV_PMU_HPMCOUNTER_FIRST 3
+#define RISCV_PMU_HPMCOUNTER_LAST \
+ (RISCV_PMU_HPMCOUNTER_FIRST + riscv_pmu->num_counters - 1)

#define RISCV_OP_UNSUPP (-EOPNOTSUPP)

+/* Hardware cache event encoding */
+#define PERF_HW_CACHE_TYPE 0
+#define PERF_HW_CACHE_OP 8
+#define PERF_HW_CACHE_RESULT 16
+#define PERF_HW_CACHE_MASK 0xff
+
+/* config_base encoding */
+#define RISCV_PMU_TYPE_MASK 0x3
+#define RISCV_PMU_TYPE_BASE 0x1
+#define RISCV_PMU_TYPE_EVENT 0x2
+#define RISCV_PMU_EXCLUDE_MASK 0xc
+#define RISCV_PMU_EXCLUDE_USER 0x3
+#define RISCV_PMU_EXCLUDE_KERNEL 0x4
+
+/*
+ * Currently, machine-mode supports emulation of mhpmeventN. Setting mhpmeventN
+ * to raise an illegal instruction exception to set event types in machine-mode.
+ * Eventually, we should set event types through standard SBI call or the shadow
+ * CSRs of supervisor-mode, because it is weird for writing CSR of machine-mode
+ * explicitly in supervisor-mode. These macro should be removed in the future.
+ */
+#define CSR_MHPMEVENT3 0x323
+#define CSR_MHPMEVENT4 0x324
+#define CSR_MHPMEVENT5 0x325
+#define CSR_MHPMEVENT6 0x326
+#define CSR_MHPMEVENT7 0x327
+#define CSR_MHPMEVENT8 0x328
+
struct cpu_hw_events {
/* # currently enabled events*/
int n_events;
/* currently enabled events */
- struct perf_event *events[RISCV_MAX_COUNTERS];
+ struct perf_event *events[RISCV_EVENT_COUNTERS];
+ /* bitmap of used event counters */
+ unsigned long used_cntr_mask;
/* vendor-defined PMU data */
void *platform;
};
diff --git a/arch/riscv/kernel/perf_event.c b/arch/riscv/kernel/perf_event.c
index c835f0362d94..0cfcd6f1e57b 100644
--- a/arch/riscv/kernel/perf_event.c
+++ b/arch/riscv/kernel/perf_event.c
@@ -139,6 +139,53 @@ static const int riscv_cache_event_map[PERF_COUNT_HW_CACHE_MAX]
},
};

+/*
+ * Methods for checking and getting PMU information
+ */
+
+static inline int is_base_counter(int idx)
+{
+ return (idx == RISCV_PMU_CYCLE || idx == RISCV_PMU_INSTRET);
+}
+
+static inline int is_event_counter(int idx)
+{
+ return (idx >= RISCV_PMU_HPMCOUNTER_FIRST &&
+ idx <= RISCV_PMU_HPMCOUNTER_LAST);
+}
+
+static inline int get_available_counter(struct perf_event *event)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ struct hw_perf_event *hwc = &event->hw;
+ unsigned long config_base = hwc->config_base & RISCV_PMU_TYPE_MASK;
+ unsigned long mask;
+ int ret;
+
+ switch (config_base) {
+ case RISCV_PMU_TYPE_BASE:
+ ret = hwc->config;
+ if (WARN_ON_ONCE(!is_base_counter(ret)))
+ return -ENOSPC;
+ break;
+ case RISCV_PMU_TYPE_EVENT:
+ mask = ~cpuc->used_cntr_mask;
+ ret = find_next_bit(&mask, RISCV_PMU_HPMCOUNTER_LAST, 3);
+ if (WARN_ON_ONCE(!is_event_counter(ret)))
+ return -ENOSPC;
+ break;
+ default:
+ return -ENOENT;
+ }
+
+ __set_bit(ret, &cpuc->used_cntr_mask);
+
+ return ret;
+}
+
+/*
+ * Map generic hardware event
+ */
static int riscv_map_hw_event(u64 config)
{
if (config >= riscv_pmu->max_events)
@@ -147,32 +194,28 @@ static int riscv_map_hw_event(u64 config)
return riscv_pmu->hw_events[config];
}

-static int riscv_map_cache_decode(u64 config, unsigned int *type,
- unsigned int *op, unsigned int *result)
-{
- return -ENOENT;
-}
-
+/*
+ * Map generic hardware cache event
+ */
static int riscv_map_cache_event(u64 config)
{
unsigned int type, op, result;
- int err = -ENOENT;
- int code;
+ int ret;

- err = riscv_map_cache_decode(config, &type, &op, &result);
- if (!riscv_pmu->cache_events || err)
- return err;
+ type = (config >> PERF_HW_CACHE_TYPE) & PERF_HW_CACHE_MASK;
+ op = (config >> PERF_HW_CACHE_OP) & PERF_HW_CACHE_MASK;
+ result = (config >> PERF_HW_CACHE_RESULT) & PERF_HW_CACHE_MASK;

if (type >= PERF_COUNT_HW_CACHE_MAX ||
op >= PERF_COUNT_HW_CACHE_OP_MAX ||
result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
return -EINVAL;

- code = (*riscv_pmu->cache_events)[type][op][result];
- if (code == RISCV_OP_UNSUPP)
+ ret = riscv_cache_event_map[type][op][result];
+ if (ret == RISCV_OP_UNSUPP)
return -EINVAL;

- return code;
+ return ret == RISCV_OP_UNSUPP ? -ENOENT : ret;
}

/*
@@ -190,8 +233,27 @@ static inline u64 read_counter(int idx)
case RISCV_PMU_INSTRET:
val = csr_read(CSR_INSTRET);
break;
+ case RISCV_PMU_HPMCOUNTER3:
+ val = csr_read(CSR_HPMCOUNTER3);
+ break;
+ case RISCV_PMU_HPMCOUNTER4:
+ val = csr_read(CSR_HPMCOUNTER4);
+ break;
+ case RISCV_PMU_HPMCOUNTER5:
+ val = csr_read(CSR_HPMCOUNTER5);
+ break;
+ case RISCV_PMU_HPMCOUNTER6:
+ val = csr_read(CSR_HPMCOUNTER6);
+ break;
+ case RISCV_PMU_HPMCOUNTER7:
+ val = csr_read(CSR_HPMCOUNTER7);
+ break;
+ case RISCV_PMU_HPMCOUNTER8:
+ val = csr_read(CSR_HPMCOUNTER8);
+ break;
default:
- WARN_ON_ONCE(idx < 0 || idx > RISCV_MAX_COUNTERS);
+ WARN_ON_ONCE(idx < RISCV_PMU_CYCLE ||
+ idx > RISCV_TOTAL_COUNTERS);
return -EINVAL;
}

@@ -204,6 +266,68 @@ static inline void write_counter(int idx, u64 value)
WARN_ON_ONCE(1);
}

+static inline void write_event(int idx, u64 value)
+{
+ /* TODO: We shouldn't write CSR of m-mode explicitly here. Ideally,
+ * it need to set the event selector by SBI call or the s-mode
+ * shadow CSRs of them. Exploit illegal instruction exception to
+ * emulate mhpmcounterN access in m-mode.
+ */
+ switch (idx) {
+ case RISCV_PMU_HPMCOUNTER3:
+ csr_write(CSR_MHPMEVENT3, value);
+ break;
+ case RISCV_PMU_HPMCOUNTER4:
+ csr_write(CSR_MHPMEVENT4, value);
+ break;
+ case RISCV_PMU_HPMCOUNTER5:
+ csr_write(CSR_MHPMEVENT5, value);
+ break;
+ case RISCV_PMU_HPMCOUNTER6:
+ csr_write(CSR_MHPMEVENT6, value);
+ break;
+ case RISCV_PMU_HPMCOUNTER7:
+ csr_write(CSR_MHPMEVENT7, value);
+ break;
+ case RISCV_PMU_HPMCOUNTER8:
+ csr_write(CSR_MHPMEVENT8, value);
+ break;
+ default:
+ WARN_ON_ONCE(idx < RISCV_PMU_HPMCOUNTER3 ||
+ idx > RISCV_TOTAL_COUNTERS);
+ return;
+ }
+}
+
+/*
+ * Enable and disable event counters
+ */
+
+static inline void riscv_pmu_enable_event(struct perf_event *event)
+{
+ struct hw_perf_event *hwc = &event->hw;
+ int idx = hwc->idx;
+
+ if (is_event_counter(idx))
+ write_event(idx, hwc->config);
+
+ /*
+ * Since we cannot write to counters, this serves as an initialization
+ * to the delta-mechanism in pmu->read(); otherwise, the delta would be
+ * wrong when pmu->read is called for the first time.
+ */
+ local64_set(&hwc->prev_count, read_counter(hwc->idx));
+}
+
+static inline void riscv_pmu_disable_event(struct perf_event *event)
+{
+ struct hw_perf_event *hwc = &event->hw;
+ int idx = hwc->idx;
+
+ if (is_event_counter(idx))
+ write_event(idx, 0);
+}
+
/*
* pmu->read: read and update the counter
*
@@ -232,6 +356,7 @@ static void riscv_pmu_read(struct perf_event *event)
*/
delta = (new_raw_count - prev_raw_count) &
((1ULL << riscv_pmu->counter_width) - 1);
+
local64_add(delta, &event->count);
/*
* Something like local64_sub(delta, &hwc->period_left) here is
@@ -252,6 +377,11 @@ static void riscv_pmu_stop(struct perf_event *event, int flags)
{
struct hw_perf_event *hwc = &event->hw;

+ if (WARN_ON_ONCE(hwc->idx == -1))
+ return;
+
+ riscv_pmu_disable_event(event);
+
WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
hwc->state |= PERF_HES_STOPPED;

@@ -271,6 +401,9 @@ static void riscv_pmu_start(struct perf_event *event, int flags)
if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
return;

+ if (WARN_ON_ONCE(hwc->idx == -1))
+ return;
+
if (flags & PERF_EF_RELOAD) {
WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));

@@ -281,14 +414,10 @@ static void riscv_pmu_start(struct perf_event *event, int flags)
}

hwc->state = 0;
- perf_event_update_userpage(event);

- /*
- * Since we cannot write to counters, this serves as an initialization
- * to the delta-mechanism in pmu->read(); otherwise, the delta would be
- * wrong when pmu->read is called for the first time.
- */
- local64_set(&hwc->prev_count, read_counter(hwc->idx));
+ riscv_pmu_enable_event(event);
+
+ perf_event_update_userpage(event);
}

/*
@@ -298,21 +427,18 @@ static int riscv_pmu_add(struct perf_event *event, int flags)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
struct hw_perf_event *hwc = &event->hw;
+ int count_idx;

if (cpuc->n_events == riscv_pmu->num_counters)
return -ENOSPC;

- /*
- * We don't have general conunters, so no binding-event-to-counter
- * process here.
- *
- * Indexing using hwc->config generally not works, since config may
- * contain extra information, but here the only info we have in
- * hwc->config is the event index.
- */
- hwc->idx = hwc->config;
- cpuc->events[hwc->idx] = event;
+ count_idx = get_available_counter(event);
+ if (count_idx < 0)
+ return -ENOSPC;
+
cpuc->n_events++;
+ hwc->idx = count_idx;
+ cpuc->events[hwc->idx] = event;

hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;

@@ -330,8 +456,10 @@ static void riscv_pmu_del(struct perf_event *event, int flags)
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
struct hw_perf_event *hwc = &event->hw;

- cpuc->events[hwc->idx] = NULL;
cpuc->n_events--;
+ __clear_bit(hwc->idx, &cpuc->used_cntr_mask);
+
+ cpuc->events[hwc->idx] = NULL;
riscv_pmu->pmu->stop(event, PERF_EF_UPDATE);
perf_event_update_userpage(event);
}
@@ -385,6 +513,7 @@ static int riscv_event_init(struct perf_event *event)
{
struct perf_event_attr *attr = &event->attr;
struct hw_perf_event *hwc = &event->hw;
+ unsigned long config_base = 0;
int err;
int code;

@@ -406,11 +535,17 @@ static int riscv_event_init(struct perf_event *event)
code = riscv_pmu->map_cache_event(attr->config);
break;
case PERF_TYPE_RAW:
- return -EOPNOTSUPP;
+ code = attr->config;
+ break;
default:
return -ENOENT;
}

+ if (is_base_counter(code))
+ config_base |= RISCV_PMU_TYPE_BASE;
+ else
+ config_base |= RISCV_PMU_TYPE_EVENT;
+
event->destroy = riscv_event_destroy;
if (code < 0) {
event->destroy(event);
@@ -424,6 +559,7 @@ static int riscv_event_init(struct perf_event *event)
* But since we don't have such support, later in pmu->add(), we just
* use hwc->config as the index instead.
*/
+ hwc->config_base = config_base;
hwc->config = code;
hwc->idx = -1;

--
2.27.0