linux-kernel - Re: [PATCH] LoongArch: Increase max supported CPUs up to 2048

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Message-ID: <728f6bff-d029-4ce5-a760-520fadee26ac@linux.dev>
Date: Wed, 7 May 2025 18:07:33 +0800
From: Yanteng Si <si.yanteng@...ux.dev>
To: Huacai Chen <chenhuacai@...ngson.cn>, Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev, Xuefeng Li <lixuefeng@...ngson.cn>,
 Guo Ren <guoren@...nel.org>, Xuerui Wang <kernel@...0n.name>,
 Jiaxun Yang <jiaxun.yang@...goat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Increase max supported CPUs up to 2048

在 5/7/25 3:34 PM, Huacai Chen 写道:
> Increase max supported CPUs up to 2048, including:
> 1. Increase CSR.CPUID register's effective width;
> 2. Define MAX_CORE_PIC (a.k.a. max physical ID) to 2048;
> 3. Allow NR_CPUS (a.k.a. max logical ID) to be as large as 2048;
> 4. Introduce acpi_numa_x2apic_affinity_init() to handle ACPI SRAT
>     for CPUID >= 256.
> 
> Note: The reason of increasing to 2048 rather than 4096/8192 is because
>        the IPI hardware can only support 2048 as a maximum.
> 
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
>   arch/loongarch/Kconfig                 |  6 ++--
>   arch/loongarch/include/asm/acpi.h      |  2 +-
>   arch/loongarch/include/asm/loongarch.h |  4 +--
>   arch/loongarch/kernel/acpi.c           | 41 ++++++++++++++++++++++----
>   4 files changed, 41 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 38706186cf13..0c356de91bc4 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -496,10 +496,10 @@ config HOTPLUG_CPU
>   	  Say N if you want to disable CPU hotplug.
>   

>   config NR_CPUS
> -	int "Maximum number of CPUs (2-256)"
> -	range 2 256
> +	int "Maximum number of CPUs (2-2048)"
> +	range 2 2048
> +	default "2048"
I'm curious. As a new architecture, why did you write
such a small value at the beginning?


Reviewed-by: Yanteng Si <si.yanteng@...ux.dev>

Thanks,
Yanteng