linux-kernel - Re: [PATCH v3 6/6] RISC-V: Do not use cpumask data structure for hartid bitmap

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Message-ID: <CAMuHMdXyjSrXNCAO8V8pajXW5ts29p==p2J1HnPPoo3-8osKbA@mail.gmail.com>
Date:   Thu, 27 Jan 2022 11:03:08 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Atish Patra <atishp@...shpatra.org>
Cc:     Jessica Clarke <jrtc27@...c27.com>,
        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>,
        Damien Le Moal <damien.lemoal@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v3 6/6] RISC-V: Do not use cpumask data structure for
 hartid bitmap

Hi Atish,

On Thu, Jan 27, 2022 at 9:48 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Thu, Jan 27, 2022 at 2:02 AM Atish Patra <atishp@...shpatra.org> wrote:
 > Ahh yes. hmask will be incorrect if the bootcpu(cpu 0) is a higher
> > hartid and it is trying to do a remote tlb flush/IPI
> > to lower the hartid. We should generate the hartid array before the loop.
> >
> > Can you try this diff ? It seems to work for me during multiple boot
> > cycle on the unleashed.
> >
> > You can find the patch here as well
> > https://github.com/atishp04/linux/commits/v5.17-rc1
>
> Thanks, that fixes the issue for me.
>
> > --- a/arch/riscv/kernel/sbi.c
> > +++ b/arch/riscv/kernel/sbi.c

> > @@ -345,13 +368,21 @@ static int __sbi_rfence_v02(int fid, const
> > struct cpumask *cpu_mask,
> >       unsigned long arg4, unsigned long arg5)
> >  {
> >   unsigned long hartid, cpuid, hmask = 0, hbase = 0;
> > - int result;
> > + int result, index = 0, max_index = 0;
> > + unsigned long hartid_arr[NR_CPUS] = {0};
>
> That's up to 256 bytes on the stack. And more if the maximum
> number of cores is increased.

I.e. 4 KiB with the proposed increase to 256 CPUs, as mentioned in
https://lore.kernel.org/all/CAAhSdy2xTW0FkwvS2dExOb7q1dVruFfTP_Vh_jWju+yi7thCeA@mail.gmail.com/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds