linux-kernel - Re: [PATCH v3] RISC-V: Increase range and default value of NR

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Date:   Thu, 18 Aug 2022 14:29:03 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Arnd Bergmann <arnd@...db.de>,
        Alistair Francis <Alistair.Francis@....com>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Anup Patel <apatel@...tanamicro.com>,
        Anup Patel <anup@...infault.org>
Subject: Re: [PATCH v3] RISC-V: Increase range and default value of NR_CPUS

On Tue, May 24, 2022 at 5:08 AM Anup Patel <anup@...infault.org> wrote:
>
> Hi Palmer,
>
> On Wed, Apr 20, 2022 at 4:54 PM Anup Patel <apatel@...tanamicro.com> wrote:
> >
> > Currently, the range and default value of NR_CPUS is too restrictive
> > for high-end RISC-V systems with large number of HARTs. The latest
> > QEMU virt machine supports upto 512 CPUs so the current NR_CPUS is
> > restrictive for QEMU as well. Other major architectures (such as
> > ARM64, x86_64, MIPS, etc) have a much higher range and default
> > value of NR_CPUS.
> >
> > This patch increases NR_CPUS range to 2-512 and default value to
> > XLEN (i.e. 32 for RV32 and 64 for RV64).
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
>
> Can this PATCH be considered for 5.19 ?
>
> Thanks,
> Anup
>
> > ---
> > Changes since v2:
> >  - Rebased on Linux-5.18-rc3
> >  - Use a different range when SBI v0.1 is enabled
> > Changes since v1:
> >  - Updated NR_CPUS range to 2-512 which reflects maximum number of
> >    CPUs supported by QEMU virt machine.
> > ---
> >  arch/riscv/Kconfig | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 00fd9c548f26..1823f281069f 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -275,10 +275,13 @@ config SMP
> >           If you don't know what to do here, say N.
> >
> >  config NR_CPUS
> > -       int "Maximum number of CPUs (2-32)"
> > -       range 2 32
> > +       int "Maximum number of CPUs (2-512)"
> >         depends on SMP
> > -       default "8"
> > +       range 2 512 if !SBI_V01
> > +       range 2 32 if SBI_V01 && 32BIT
> > +       range 2 64 if SBI_V01 && 64BIT
> > +       default "32" if 32BIT
> > +       default "64" if 64BIT
> >
> >  config HOTPLUG_CPU
> >         bool "Support for hot-pluggable CPUs"
> > --
> > 2.25.1
> >


Ping ?
It would be useful to include this patch sooner than later to enable
high HART count testing by default.


-- 
Regards,
Atish