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

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Message-ID: <87o83xtrdc.fsf@igel.home>
Date:   Thu, 27 Jan 2022 11:17:19 +0100
From:   Andreas Schwab <schwab@...ux-m68k.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Atish Patra <atishp@...shpatra.org>,
        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

On Jan 27 2022, Geert Uytterhoeven wrote:

> 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

And those 4K need to be cleared each time the function is called, even
if there is only a small number of cpus.

-- 
Andreas Schwab, schwab@...ux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."