linux-kernel - Re: [PATCH] ACPI: boot correctly with "nosmp" or "maxcpus=0"

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Message-ID: <20070816193649.GA16680@bingen.suse.de>
Date:	Thu, 16 Aug 2007 21:36:49 +0200
From:	Andi Kleen <ak@...e.de>
To:	Len Brown <lenb@...nel.org>
Cc:	Andi Kleen <ak@...e.de>, linux-acpi@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI: boot correctly with "nosmp" or "maxcpus=0"

> @@ -157,10 +162,13 @@ early_param("nosmp", nosmp);
>  static int __init maxcpus(char *str)
>  {
>  	get_option(&str, &max_cpus);
> -	return 1;
> +	if (max_cpus == 0)
> +		disable_ioapic_setup();

I must say I never liked that maxcpus=0 ... does disable the APIC
too. There can be situations where you want only a single CPU,
but still full APICs because modern systems don't boot without. 

It's the old traditional documented semantics though,
but on the other hand if it never worked with ACPI i guess people are
not relying on it.

So perhaps it would be better to change that? 
Or add a new option to limit CPUs without disabling ACPIC?

-Andi
-
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