[RFC 1/9] RISC-V: Define a helper function to probe number of hardware counters

Atish Patra
2022-07-18T17:06:05Z

KVM module needs to know how many hardware counters the platform supports.
Otherwise, it will not be able to show optimal value of virtual
counters to the guest.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
drivers/perf/riscv_pmu_sbi.c | 23 +++++++++++++++++------
include/linux/perf/riscv_pmu.h | 4 ++++
2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 24124546844c..1723af68ffa1 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -27,6 +27,7 @@
*/
static union sbi_pmu_ctr_info *pmu_ctr_list;
static unsigned int riscv_pmu_irq;
+static struct riscv_pmu *rvpmu;

struct sbi_pmu_event_data {
union {
@@ -227,6 +228,12 @@ static const struct sbi_pmu_event_data pmu_cache_event_map[PERF_COUNT_HW_CACHE_M
},
};

+int riscv_pmu_sbi_get_num_hw_ctrs(void)
+{
+ return rvpmu ? rvpmu->num_hw_counters : 0;
+}
+EXPORT_SYMBOL(riscv_pmu_sbi_get_num_hw_ctrs);
+
static int pmu_sbi_ctr_get_width(int idx)
{
return pmu_ctr_list[idx].width;
@@ -443,7 +450,7 @@ static int pmu_sbi_find_num_ctrs(void)
return sbi_err_map_linux_errno(ret.error);
}

-static int pmu_sbi_get_ctrinfo(int nctr)
+static int pmu_sbi_get_ctrinfo(int nctr, int *num_hw_ctrs)
{
struct sbiret ret;
int i, num_hw_ctr = 0, num_fw_ctr = 0;
@@ -453,7 +460,7 @@ static int pmu_sbi_get_ctrinfo(int nctr)
if (!pmu_ctr_list)
return -ENOMEM;

- for (i = 0; i <= nctr; i++) {
+ for (i = 0; i < nctr; i++) {
ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_GET_INFO, i, 0, 0, 0, 0, 0);
if (ret.error)
/* The logical counter ids are not expected to be contiguous */
@@ -466,6 +473,7 @@ static int pmu_sbi_get_ctrinfo(int nctr)
pmu_ctr_list[i].value = cinfo.value;
}

+ *num_hw_ctrs = num_hw_ctr;
pr_info("%d firmware and %d hardware counters\n", num_fw_ctr, num_hw_ctr);

return 0;
@@ -698,7 +706,7 @@ static int pmu_sbi_setup_irqs(struct riscv_pmu *pmu, struct platform_device *pde
static int pmu_sbi_device_probe(struct platform_device *pdev)
{
struct riscv_pmu *pmu = NULL;
- int num_counters;
+ int num_counters, num_hw_ctrs = 0;
int ret = -ENODEV;

pr_info("SBI PMU extension is available\n");
@@ -713,7 +721,7 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
}

/* cache all the information about counters now */
- if (pmu_sbi_get_ctrinfo(num_counters))
+ if (pmu_sbi_get_ctrinfo(num_counters, &num_hw_ctrs))
goto out_free;

ret = pmu_sbi_setup_irqs(pmu, pdev);
@@ -723,6 +731,7 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
pmu->pmu.capabilities |= PERF_PMU_CAP_NO_EXCLUDE;
}
pmu->num_counters = num_counters;
+ pmu->num_hw_counters = num_hw_ctrs;
pmu->ctr_start = pmu_sbi_ctr_start;
pmu->ctr_stop = pmu_sbi_ctr_stop;
pmu->event_map = pmu_sbi_event_map;
@@ -733,14 +742,16 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)

ret = cpuhp_state_add_instance(CPUHP_AP_PERF_RISCV_STARTING, &pmu->node);
if (ret)
- return ret;
+ goto out_free;

ret = perf_pmu_register(&pmu->pmu, "cpu", PERF_TYPE_RAW);
if (ret) {
cpuhp_state_remove_instance(CPUHP_AP_PERF_RISCV_STARTING, &pmu->node);
- return ret;
+ goto out_free;
}

+ rvpmu = pmu;
+
return 0;

out_free:
diff --git a/include/linux/perf/riscv_pmu.h b/include/linux/perf/riscv_pmu.h
index 46f9b6fe306e..fc47167e000c 100644
--- a/include/linux/perf/riscv_pmu.h
+++ b/include/linux/perf/riscv_pmu.h
@@ -46,6 +46,7 @@ struct riscv_pmu {
irqreturn_t (*handle_irq)(int irq_num, void *dev);

int num_counters;
+ int num_hw_counters;
u64 (*ctr_read)(struct perf_event *event);
int (*ctr_get_idx)(struct perf_event *event);
int (*ctr_get_width)(int idx);
@@ -69,6 +70,9 @@ void riscv_pmu_legacy_skip_init(void);
static inline void riscv_pmu_legacy_skip_init(void) {};
#endif
struct riscv_pmu *riscv_pmu_alloc(void);
+#ifdef CONFIG_RISCV_PMU_SBI
+int riscv_pmu_sbi_get_num_hw_ctrs(void);
+#endif

#endif /* CONFIG_RISCV_PMU */

--
2.25.1