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Subject: Re: [PATCH] LoongArch: Let cores_io_master cover the largest NR_CPUS
From: Xi Ruoyao <xry111@xry111.site>
To: Huacai Chen <chenhuacai@kernel.org>, maobibo <maobibo@loongson.cn>
Cc: loongson-kernel@lists.loongnix.cn, loongarch@lists.linux.dev, Xuefeng Li
	 <lixuefeng@loongson.cn>, Guo Ren <guoren@kernel.org>, Xuerui Wang
	 <kernel@xen0n.name>, Jiaxun Yang <jiaxun.yang@flygoat.com>, 
	linux-kernel@vger.kernel.org, Huacai Chen <chenhuacai@loongson.cn>
Date: Mon, 25 Dec 2023 19:11:19 +0800
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References: <20231225070002.1350705-1-chenhuacai@loongson.cn>
	 <3db5c086-db9b-cb3a-5521-44f18cb55c4a@loongson.cn>
	 <CAAhV-H5Rs4BGKHZrA5bxSh0=4uhPx7vbVwBXtdtfU4hemN2QjA@mail.gmail.com>
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On Mon, 2023-12-25 at 17:19 +0800, Huacai Chen wrote:
> On Mon, Dec 25, 2023 at 5:13=E2=80=AFPM maobibo <maobibo@loongson.cn> wro=
te:
> >=20
> >=20
> >=20
> > On 2023/12/25 =E4=B8=8B=E5=8D=883:00, Huacai Chen wrote:
> > > Now loongson_system_configuration::cores_io_master only covers 64 cpu=
s,
> > > if NR_CPUS > 64 there will be memory corruption. So let cores_io_mast=
er
> > > cover the largest NR_CPUS (256).
> > >=20
> > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > > ---
> > > =C2=A0=C2=A0 arch/loongarch/include/asm/bootinfo.h | 4 ++--
> > > =C2=A0=C2=A0 arch/loongarch/kernel/acpi.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 2 +-
> > > =C2=A0=C2=A0 arch/loongarch/kernel/smp.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 2 +-
> > > =C2=A0=C2=A0 3 files changed, 4 insertions(+), 4 deletions(-)
> > >=20
> > > diff --git a/arch/loongarch/include/asm/bootinfo.h b/arch/loongarch/i=
nclude/asm/bootinfo.h
> > > index c60796869b2b..32fd0319594a 100644
> > > --- a/arch/loongarch/include/asm/bootinfo.h
> > > +++ b/arch/loongarch/include/asm/bootinfo.h
> > > @@ -30,7 +30,7 @@ struct loongson_system_configuration {
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 int boot_cpu_id;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 int cores_per_node;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 int cores_per_package;
> > > -=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long cores_io_master;
> > > +=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long cores_io_master[4];
> > Can the hardcoded 4 be defined something like this?
> > =C2=A0=C2=A0=C2=A0=C2=A0 DIV_ROUND_UP(CONFIG_NR_CPUS, sizeof(long))
> Can this be used to define arrays?

Yes, it's basically just expanded to (((CONFIG_NR_CPUS) + (sizeof(long))
- 1) / (sizeof(long)).  Per the C standard (C99 section 6.6 p6) it's an
integer constant expression and can be used as array size.

--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University