RISC-V: Update user page mapping only once during start

Currently, riscv_pmu_event_set_period updates the userpage mapping.
However, the caller of riscv_pmu_event_set_period should update
the userpage mapping because the counter can not be updated/started
from set_period function in counter overflow path.

Invoke the perf_event_update_userpage at the caller so that it
doesn't get invoked twice during counter start path.

Fixes: f5bfa23 ("RISC-V: Add a perf core library for pmu drivers")
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220711174632.4186047-3-atishp@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: atishp04

drivers/perf/riscv_pmu.c

@@ -170,7 +170,6 @@ int riscv_pmu_event_set_period(struct perf_event *event)
 		left = (max_period >> 1);
 
 	local64_set(&hwc->prev_count, (u64)-left);
-	perf_event_update_userpage(event);
 
 	return overflow;
 }

drivers/perf/riscv_pmu_sbi.c

@@ -532,6 +532,7 @@ static inline void pmu_sbi_start_overflow_mask(struct riscv_pmu *pmu,
 			sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_START, idx, 1,
 				  flag, init_val, 0, 0);
 #endif
+			perf_event_update_userpage(event);
 		}
 		ctr_ovf_mask = ctr_ovf_mask >> 1;
 		idx++;