perf: RISC-V: exclude invalid pmu counters from SBI calls

SBI firmware may not provide information for some counters in response
to SBI_EXT_PMU_COUNTER_GET_INFO call. Exclude such counters from the
subsequent SBI requests. For this purpose use global mask to keep track
of fully specified counters.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20220830155306.301714-3-geomatsi@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: sm-sc

drivers/perf/riscv_pmu_legacy.c

@@ -14,7 +14,6 @@
 
 #define RISCV_PMU_LEGACY_CYCLE		0
 #define RISCV_PMU_LEGACY_INSTRET	1
-#define RISCV_PMU_LEGACY_NUM_CTR	2
 
 static bool pmu_init_done;
 
@@ -83,7 +82,8 @@ static void pmu_legacy_init(struct riscv_pmu *pmu)
 {
 	pr_info("Legacy PMU implementation is available\n");
 
-	pmu->num_counters = RISCV_PMU_LEGACY_NUM_CTR;
+	pmu->cmask = BIT(RISCV_PMU_LEGACY_CYCLE) |
+		BIT(RISCV_PMU_LEGACY_INSTRET);
 	pmu->ctr_start = pmu_legacy_ctr_start;
 	pmu->ctr_stop = NULL;
 	pmu->event_map = pmu_legacy_event_map;

drivers/perf/riscv_pmu_sbi.c

@@ -271,7 +271,6 @@ static int pmu_sbi_ctr_get_idx(struct perf_event *event)
 	struct sbiret ret;
 	int idx;
 	uint64_t cbase = 0;
-	uint64_t cmask = GENMASK_ULL(rvpmu->num_counters - 1, 0);
 	unsigned long cflags = 0;
 
 	if (event->attr.exclude_kernel)
@@ -281,11 +280,12 @@ static int pmu_sbi_ctr_get_idx(struct perf_event *event)
 
 	/* retrieve the available counter index */
 #if defined(CONFIG_32BIT)
-	ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_CFG_MATCH, cbase, cmask,
-			cflags, hwc->event_base, hwc->config, hwc->config >> 32);
+	ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_CFG_MATCH, cbase,
+			rvpmu->cmask, cflags, hwc->event_base, hwc->config,
+			hwc->config >> 32);
 #else
-	ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_CFG_MATCH, cbase, cmask,
-			cflags, hwc->event_base, hwc->config, 0);
+	ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_CFG_MATCH, cbase,
+			rvpmu->cmask, cflags, hwc->event_base, hwc->config, 0);
 #endif
 	if (ret.error) {
 		pr_debug("Not able to find a counter for event %lx config %llx\n",
@@ -294,7 +294,7 @@ static int pmu_sbi_ctr_get_idx(struct perf_event *event)
 	}
 
 	idx = ret.value;
-	if (idx >= rvpmu->num_counters || !pmu_ctr_list[idx].value)
+	if (!test_bit(idx, &rvpmu->cmask) || !pmu_ctr_list[idx].value)
 		return -ENOENT;
 
 	/* Additional sanity check for the counter id */
@@ -463,7 +463,7 @@ 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, unsigned long *mask)
 {
 	struct sbiret ret;
 	int i, num_hw_ctr = 0, num_fw_ctr = 0;
@@ -478,6 +478,9 @@ static int pmu_sbi_get_ctrinfo(int nctr)
 		if (ret.error)
 			/* The logical counter ids are not expected to be contiguous */
 			continue;
+
+		*mask |= BIT(i);
+
 		cinfo.value = ret.value;
 		if (cinfo.type == SBI_PMU_CTR_TYPE_FW)
 			num_fw_ctr++;
@@ -498,7 +501,7 @@ static inline void pmu_sbi_stop_all(struct riscv_pmu *pmu)
 	 * which may include counters that are not enabled yet.
 	 */
 	sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_STOP,
-		  0, GENMASK_ULL(pmu->num_counters - 1, 0), 0, 0, 0, 0);
+		  0, pmu->cmask, 0, 0, 0, 0);
 }
 
 static inline void pmu_sbi_stop_hw_ctrs(struct riscv_pmu *pmu)
@@ -788,8 +791,9 @@ static void riscv_pmu_destroy(struct riscv_pmu *pmu)
 static int pmu_sbi_device_probe(struct platform_device *pdev)
 {
 	struct riscv_pmu *pmu = NULL;
-	int num_counters;
+	unsigned long cmask = 0;
 	int ret = -ENODEV;
+	int num_counters;
 
 	pr_info("SBI PMU extension is available\n");
 	pmu = riscv_pmu_alloc();
@@ -803,7 +807,7 @@ 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, &cmask))
 		goto out_free;
 
 	ret = pmu_sbi_setup_irqs(pmu, pdev);
@@ -812,8 +816,9 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 		pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;
 		pmu->pmu.capabilities |= PERF_PMU_CAP_NO_EXCLUDE;
 	}
+
 	pmu->pmu.attr_groups = riscv_pmu_attr_groups;
-	pmu->num_counters = num_counters;
+	pmu->cmask = cmask;
 	pmu->ctr_start = pmu_sbi_ctr_start;
 	pmu->ctr_stop = pmu_sbi_ctr_stop;
 	pmu->event_map = pmu_sbi_event_map;

include/linux/perf/riscv_pmu.h

@@ -45,7 +45,7 @@ struct riscv_pmu {
 
 	irqreturn_t	(*handle_irq)(int irq_num, void *dev);
 
-	int		num_counters;
+	unsigned long	cmask;
 	u64		(*ctr_read)(struct perf_event *event);
 	int		(*ctr_get_idx)(struct perf_event *event);
 	int		(*ctr_get_width)(int idx);