linux-kernel - Re: arch/riscv: disable too many harts before pick main boot hart

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Date:   Thu, 19 Sep 2019 03:24:55 +0000
From:   Xiang Wang <merle@...denedlinux.org>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "citypw@...denedlinux.org" <citypw@...denedlinux.org>
Subject: Re: arch/riscv: disable too many harts before pick main boot hart






‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On 2019年9月14日SaturdayAM3点04分, Palmer Dabbelt <palmer@...ive.com> wrote:

> On Thu, 05 Sep 2019 23:51:15 PDT (-0700), merle@...denedlinux.org wrote:
>
> > From 12300865d1103618c9d4c375f7d7fbe601b6618c Mon Sep 17 00:00:00 2001
> > From: Xiang Wang merle@...denedlinux.org
> > Date: Fri, 6 Sep 2019 11:56:09 +0800
> > Subject: [PATCH] arch/riscv: disable too many harts before pick main boot hart
> > These harts with id greater than or equal to CONFIG_NR_CPUS need to be disabled.
> > But pick the main Hart can choose any one. So, before pick the main hart, you
> > need to disable the hart with id greater than or equal to CONFIG_NR_CPUS.
> >
> > Signed-off-by: Xiang Wang merle@...denedlinux.org
> >
> > --------------------------------------------------
> >
> > arch/riscv/kernel/head.S | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> > index 0f1ba17e476f..cfffea38eb17 100644
> > --- a/arch/riscv/kernel/head.S
> > +++ b/arch/riscv/kernel/head.S
> > @@ -63,6 +63,11 @@ _start_kernel:
> > li t0, SR_FS
> > csrc sstatus, t0
> > +#ifdef CONFIG_SMP
> >
> > -   li t0, CONFIG_NR_CPUS
> > -   bgeu a0, t0, .Lsecondary_park
> >     +#endif
> >
> > -
> >
> > /* Pick one hart to run the main boot sequence */
> > la a3, hart_lottery
> > li a2, 1
> > @@ -154,9 +159,6 @@ relocate:
> > .Lsecondary_start:
> > #ifdef CONFIG_SMP
> >
> > -   li a1, CONFIG_NR_CPUS
> > -   bgeu a0, a1, .Lsecondary_park
> > -
> >
> > /* Set trap vector to spin forever to help debug */
> > la a3, .Lsecondary_park
> > csrw CSR_STVEC, a3
>
> It would be better to decouple the hart masks from NR_CPUS, as there's really
> no reason for these to be the same.

This may be new feature. Need to define new macros such as disabled_hart_mask,
this patch is used to fix bug and not add new feature.

>
> Reviewed-by: Palmer Dabbelt palmer@...ive.com