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References: <20220711174632.4186047-1-atishp@rivosinc.com> <20220711174632.4186047-3-atishp@rivosinc.com>
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From:   Guo Ren <guoren@kernel.org>
Date:   Tue, 12 Jul 2022 09:54:30 +0800
Message-ID: <CAJF2gTT=0S-_nCM-+SHUNkG0i-h1zBca_KwgRgsZ8BBE-DPG_w@mail.gmail.com>
Subject: Re: [v3 2/5] RISC-V: Update user page mapping only once during start
To:     Atish Patra <atishp@rivosinc.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Anup Patel <anup@brainfault.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Atish Patra <atishp@atishpatra.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Will Deacon <will@kernel.org>
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Good catch, Is there any bug report?

Anyway:
Reviewed-by: Guo Ren <guoren@kernel.org>


On Tue, Jul 12, 2022 at 1:46 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> 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")
>
> Reviewed-by: Anup Patel <anup@brainfault.org>
> Signed-off-by: Atish Patra <atishp@rivosinc.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 0cb694b794ae..3735337a4cfb 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/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++;
> --
> 2.25.1
>


--
Best Regards
 Guo Ren