linux-kernel - [PATCH 2/2] RISC-V: Update user page mapping only once during start

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Message-Id: <20220511201107.2311757-2-atishp@rivosinc.com>
Date:   Wed, 11 May 2022 13:11:07 -0700
From:   Atish Patra <atishp@...osinc.com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        Damien Le Moal <damien.lemoal@....com>,
        devicetree@...r.kernel.org, Jisheng Zhang <jszhang@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        linux-riscv@...ts.infradead.org,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: [PATCH 2/2] 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: f5bfa23f576f ("RISC-V: Add a perf core library for pmu drivers")

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 drivers/perf/riscv_pmu.c     | 1 -
 drivers/perf/riscv_pmu_sbi.c | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/perf/riscv_pmu.c b/drivers/perf/riscv_pmu.c
index b2b8d2074ed0..130b9f1a40e0 100644
--- a/drivers/perf/riscv_pmu.c
+++ b/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;
 }
diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 24cea59612be..2eac5db2cc18 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -527,6 +527,7 @@ static inline void pmu_sbi_start_overflow_mask(struct riscv_pmu *pmu,
 			init_val = local64_read(&hwc->prev_count) & max_period;
 			sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_START, idx, 1,
 				  flag, init_val, init_val >> 32, 0);
+			perf_event_update_userpage(event);
 		}
 		ctr_ovf_mask = ctr_ovf_mask >> 1;
 		idx++;
-- 
2.25.1