linux-kernel - Re: PCI MSI breaks when booting with nosmp

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Message-ID: <480CEDE5.3060008@firstfloor.org>
Date:	Mon, 21 Apr 2008 21:41:25 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	linux-pci@...ey.karlin.mff.cuni.cz,
	Jean Delvare <jdelvare@...e.de>,
	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
	Tejun Heo <htejun@...il.com>,
	Tom Long Nguyen <tom.l.nguyen@...el.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Jeff Garzik <jgarzik@...ox.com>
Subject: Re: PCI MSI breaks when booting with nosmp

Jesse Barnes wrote:
> On Monday, April 21, 2008 11:45 am Andi Kleen wrote:
>> Jesse Barnes <jbarnes@...tuousgeek.org> writes:
>>> Ok, I see this too on my desktop machine.  It looks like we're not
>>> getting interrupts setup correctly in the nosmp case.  Still digging
>>> through to see why though...
>> NoSMP disables the io-apic and a lot of modern systems don't work without
>> APIC.
>>
>> If you just want to run with a single cpu for testing etc. always use
>> maxcpus=1 (not 0, that will disable the APIC too)
> 
> Right...  but it looks like the MSI code is buggy when noapic is specified via 
> nosmp or maxcpus=0.  We should either fix it to work with noapic or disable 
> it like we do the ioapic when nosmp or maxcpus=0:

First that would likely not compile on architectures without PCI?

Also there is more code in the guts of arch/x86 that disables the
IO-APIC and likely has the same problem. Best probably you put it all
into a single function that does it all properly instead of continuning
to open code it.

Just don't break the other architectures in main.c

-Andi
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