linux-kernel - Re: [v3 2/5] RISC-V: Update user page mapping only once during start

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Date:   Tue, 12 Jul 2022 17:59:25 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Guo Ren <guoren@...nel.org>
Cc:     Atish Patra <atishp@...osinc.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Anup Patel <anup@...infault.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [v3 2/5] RISC-V: Update user page mapping only once during start

On Mon, Jul 11, 2022 at 6:54 PM Guo Ren <guoren@...nel.org> wrote:
>
> Good catch, Is there any bug report?
>

Not that I know of.

> Anyway:
> Reviewed-by: Guo Ren <guoren@...nel.org>
>
>
> On Tue, Jul 12, 2022 at 1:46 AM Atish Patra <atishp@...osinc.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@...infault.org>
> > 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 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



-- 
Regards,
Atish