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From: Jean Delvare <jdelvare@suse.de>
Organization: SuSE Linux
To: Andi Kleen <andi@firstfloor.org>
Subject: Re: PCI MSI breaks when booting with nosmp
Date: Mon, 21 Apr 2008 22:48:02 +0200
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Cc: Jesse Barnes <jbarnes@virtuousgeek.org>,
       linux-pci@atrey.karlin.mff.cuni.cz, LKML <linux-kernel@vger.kernel.org>,
       Pavel Machek <pavel@ucw.cz>, Tejun Heo <htejun@gmail.com>,
       Tom Long Nguyen <tom.l.nguyen@intel.com>,
       Randy Dunlap <rdunlap@xenotime.net>, Jeff Garzik <jgarzik@pobox.com>
References: <200804172140.02311.jdelvare@suse.de> <200804212220.20577.jdelvare@suse.de> <20080421204651.GB21028@one.firstfloor.org>
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Hi Andi,

Le lundi 21 avril 2008, Andi Kleen a écrit :
> > In my case, booting with noapic works fine, so I don't think that the problem
> > is related to APIC being disabled.
> 
> noapic is not the same as no ioapic. maxcpus=0 just disables the IO-APIC
> but not the local APIC.

>>From init/main.c:

static int __init maxcpus(char *str)
{
	get_option(&str, &setup_max_cpus);
	if (setup_max_cpus == 0)
		disable_ioapic_setup();

	return 0;
}
early_param("maxcpus", maxcpus);

>>From arch/x86/kernel/io_apic_32.c:

static int __init parse_noapic(char *arg)
{
	/* disable IO-APIC */
	disable_ioapic_setup();
	return 0;
}
early_param("noapic", parse_noapic);

Both call disable_ioapic_setup(), so how can they not be the same?

-- 
Jean Delvare
Suse L3