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

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Date:   Thu, 27 Jan 2022 09:48:53 +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

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:
> > On Wed, Jan 26, 2022 at 1:10 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > On Wed, Jan 26, 2022 at 9:28 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > > On Wed, Jan 26, 2022 at 3:21 AM Atish Patra <atishp@...shpatra.org> wrote:
> > > > > On Tue, Jan 25, 2022 at 2:26 PM Jessica Clarke <jrtc27@...c27.com> wrote:
> > > > > > On 20 Jan 2022, at 09:09, Atish Patra <atishp@...osinc.com> wrote:
> > > > > > > Currently, SBI APIs accept a hartmask that is generated from struct
> > > > > > > cpumask. Cpumask data structure can hold upto NR_CPUs value. Thus, it
> > > > > > > is not the correct data structure for hartids as it can be higher
> > > > > > > than NR_CPUs for platforms with sparse or discontguous hartids.
> > > > > > >
> > > > > > > Remove all association between hartid mask and struct cpumask.
> > > > > > >
> > > > > > > Reviewed-by: Anup Patel <anup@...infault.org> (For Linux RISC-V changes)
> > > > > > > Acked-by: Anup Patel <anup@...infault.org> (For KVM RISC-V changes)
> > > > > > > Signed-off-by: Atish Patra <atishp@...osinc.com>
> > > >
> > > > > I am yet to reproduce it on my end.
> > > > > @Geert Uytterhoeven: can you please try the below diff on your end.
> > > >
> > > > Unfortunately it doesn't fix the issue for me.
> > > >
> > > > /me debugging...
> > >
> > > Found it: after this commit, the SBI_EXT_RFENCE_REMOTE_FENCE_I and
> > > SBI_EXT_RFENCE_REMOTE_SFENCE_VMA ecalls are now called with
> > > hmask = 0x8000000000000001 and hbase = 1 instead of hmask = 3 and
> > > hbase = 0.
> > >
> > > cpuid 1 maps to  hartid 0
> > > cpuid 0 maps to hartid 1
> > >
> > >     __sbi_rfence_v02:364: cpuid 1 hartid 0
> > >     __sbi_rfence_v02:377: hartid 0 hbase 1
> > >     hmask |= 1UL << (hartid - hbase);
> > >
> > > oops
> > >
> > >     __sbi_rfence_v02_call:303: SBI_EXT_RFENCE_REMOTE_FENCE_I hmask
> > > 8000000000000001 hbase 1
> > >
> >
> > 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.

Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>

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