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Date: Mon, 21 Apr 2008 23:09:09 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Jean Delvare <jdelvare@suse.de>
Cc: Andi Kleen <andi@firstfloor.org>, 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>
Subject: Re: PCI MSI breaks when booting with nosmp
Message-ID: <20080421210909.GC21028@one.firstfloor.org>
References: <200804172140.02311.jdelvare@suse.de> <200804212220.20577.jdelvare@suse.de> <20080421204651.GB21028@one.firstfloor.org> <200804212248.02986.jdelvare@suse.de>
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> Both call disable_ioapic_setup(), so how can they not be the same?

See Jesse's explanation. Basically there is special code in the smp 
boot up to handle 0 CPUs and it disables all APICs.

This is very old and crufty and somewhat obsolete logic,
but it is like that.

-Andi