linux-kernel - Re: [PATCH v9 1/7] RISC-V: Clear SIP bit only when using SBI IPI operations

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Message-ID: <CAK9=C2XMgRAwu4ALhcRkJJnsCdms6rR7DqG3Nz7ZJa9cX+RP8Q@mail.gmail.com>
Date:   Thu, 8 Sep 2022 18:07:18 +0530
From:   Anup Patel <apatel@...tanamicro.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Atish Patra <atishp@...shpatra.org>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Bin Meng <bmeng.cn@...il.com>
Subject: Re: [PATCH v9 1/7] RISC-V: Clear SIP bit only when using SBI IPI operations

On Thu, Sep 8, 2022 at 2:08 PM Marc Zyngier <maz@...nel.org> wrote:
>
> On Sat, 03 Sep 2022 17:13:03 +0100,
> Anup Patel <apatel@...tanamicro.com> wrote:
> >
> > The software interrupt pending (i.e. [M|S]SIP) bit is writeable for
> > S-mode but read-only for M-mode so we clear this bit only when using
> > SBI IPI operations.
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > Reviewed-by: Bin Meng <bmeng.cn@...il.com>
> > ---
> >  arch/riscv/kernel/sbi.c | 8 +++++++-
> >  arch/riscv/kernel/smp.c | 2 --
> >  2 files changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> > index 775d3322b422..fc614650a2e3 100644
> > --- a/arch/riscv/kernel/sbi.c
> > +++ b/arch/riscv/kernel/sbi.c
> > @@ -643,8 +643,14 @@ static void sbi_send_cpumask_ipi(const struct cpumask *target)
> >       sbi_send_ipi(target);
> >  }
> >
> > +static void sbi_ipi_clear(void)
> > +{
> > +     csr_clear(CSR_IP, IE_SIE);
> > +}
> > +
> >  static const struct riscv_ipi_ops sbi_ipi_ops = {
> > -     .ipi_inject = sbi_send_cpumask_ipi
> > +     .ipi_inject = sbi_send_cpumask_ipi,
> > +     .ipi_clear = sbi_ipi_clear
> >  };
> >
> >  void __init sbi_init(void)
> > diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
> > index 760a64518c58..c56d67f53ea9 100644
> > --- a/arch/riscv/kernel/smp.c
> > +++ b/arch/riscv/kernel/smp.c
> > @@ -83,8 +83,6 @@ void riscv_clear_ipi(void)
> >  {
> >       if (ipi_ops && ipi_ops->ipi_clear)
> >               ipi_ops->ipi_clear();
> > -
> > -     csr_clear(CSR_IP, IE_SIE);
> >  }
> >  EXPORT_SYMBOL_GPL(riscv_clear_ipi);
>
> This really begs the question: why on Earth are these things exported
> to *modules*? I cannot see a good reason why they should be...

I agree, the riscv_clear_ipi() should not be exported but the PATCH4
("RISC-V: Treat IPIs as normal Linux IRQs") of this series removes
this function.

Regards,
Anup

>
>         M>
>
> --
> Without deviation from the norm, progress is not possible.