drivers/perf: riscv: Do not allow invalid raw event config

The SBI specification allows only lower 48bits of hpmeventX to be
configured via SBI PMU. Currently, the driver masks of the higher
bits but doesn't return an error. This will lead to an additional
SBI call for config matching which should return for an invalid
event error in most of the cases.

However, if a platform(i.e Rocket and sifive cores) implements a
bitmap of all bits in the event encoding this will lead to an
incorrect event being programmed leading to user confusion.

Report the error to the user if higher bits are set during the
event mapping itself to avoid the confusion and save an additional
SBI call.

Suggested-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241212-pmu_event_fixes_v2-v2-3-813e8a4f5962@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index da3651d329069c18f54ef4b1615ef908b59c956b..194c153e5d71c62a48fe133db360ae21c96d5166 100644 (file)
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -536,8 +536,11 @@ static int pmu_sbi_event_map(struct perf_event *event, u64 *econfig)
 
                switch (config >> 62) {
                case 0:
-                       ret = RISCV_PMU_RAW_EVENT_IDX;
-                       *econfig = config & RISCV_PMU_RAW_EVENT_MASK;
+                       /* Return error any bits [48-63] is set  as it is not allowed by the spec */
+                       if (!(config & ~RISCV_PMU_RAW_EVENT_MASK)) {
+                               *econfig = config & RISCV_PMU_RAW_EVENT_MASK;
+                               ret = RISCV_PMU_RAW_EVENT_IDX;
+                       }
                        break;
                case 2:
                        ret = (config & 0xFFFF) | (SBI_PMU_EVENT_TYPE_FW << 16);