linux-kernel - Re: [PATCH] arm: allow single CPU configuration by adjusting NR

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Message-ID: <aIJxVDBXyFgrz8AV@shell.armlinux.org.uk>
Date: Thu, 24 Jul 2025 18:45:56 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Suchit Karunakaran <suchitkarunakaran@...il.com>
Cc: ardb@...nel.org, linus.walleij@...aro.org, ebiggers@...gle.com,
	nathan@...nel.org, lumag@...nel.org, dave@...ilevsky.ca,
	ruanjinjie@...wei.com, kees@...nel.org, liuyuntao12@...wei.com,
	linux-arm-kernel@...ts.infradead.org, skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: allow single CPU configuration by adjusting NR_CPUS
 range and defaults

On Thu, Jul 24, 2025 at 10:56:03PM +0530, Suchit Karunakaran wrote:
> Previously, the NR_CPUS config for ARM required a minimum of 2 CPUs.
> This patch changes the minimum NR_CPUS to 1 when SMP is not enabled,
> sets range to exactly 1 if !SMP, allowing only a single CPU setting and
> adds conditional defaults:
>     - default to 1 if SMP is disabled (uniprocessor)
>     - default to 4 if SMP is enabled (multiprocessor)
> 
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>

This hasn't been tested. NR_CPUS depends on SMP, so if SMP is not
enabled, then NR_CPUS doesn't exist in the configuration. Therefore,
providing a default for !SMP is meaningless. 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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