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

From: Andreas Schwab <schwab@linux-m68k.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Atish Patra <atishp@atishpatra.org>,
	 Jessica Clarke <jrtc27@jrtc27.com>,
	 Atish Patra <atishp@rivosinc.com>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	 Anup Patel <anup@brainfault.org>,
	 Albert Ou <aou@eecs.berkeley.edu>,
	 Damien Le Moal <damien.lemoal@wdc.com>,
	 devicetree <devicetree@vger.kernel.org>,
	Jisheng Zhang <jszhang@kernel.org>,
	 Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	 linux-riscv <linux-riscv@lists.infradead.org>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	 Rob Herring <robh+dt@kernel.org>
Subject: Re: [PATCH v3 6/6] RISC-V: Do not use cpumask data structure for hartid bitmap
Date: Thu, 27 Jan 2022 11:17:19 +0100	[thread overview]
Message-ID: <87o83xtrdc.fsf@igel.home> (raw)
In-Reply-To: <CAMuHMdXyjSrXNCAO8V8pajXW5ts29p==p2J1HnPPoo3-8osKbA@mail.gmail.com> (Geert Uytterhoeven's message of "Thu, 27 Jan 2022 11:03:08 +0100")

On Jan 27 2022, Geert Uytterhoeven wrote:

> Hi Atish,
>
> On Thu, Jan 27, 2022 at 9:48 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>> On Thu, Jan 27, 2022 at 2:02 AM Atish Patra <atishp@atishpatra.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@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

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