linux-kernel - Re: Why do so many machines need "noapic"?

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Message-ID: <20070924213224.GI8127@redhat.com>
Date:	Mon, 24 Sep 2007 17:32:24 -0400
From:	Dave Jones <davej@...hat.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Oeser <ioe-lkml@...eria.de>,
	Andi Kleen <andi@...stfloor.org>,
	Chuck Ebbert <cebbert@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Why do so many machines need "noapic"?

On Sat, Sep 15, 2007 at 01:08:25PM +0100, Matthew Garrett wrote:
 > On Sat, Sep 15, 2007 at 04:08:02AM -0700, Andrew Morton wrote:
 > 
 > > I believe that about two years ago we broke something which caused quite a
 > > large number of people to need noapic.  Is that the case with any of your
 > > machines?  Do you know if they run 2.6.ancient without noapic?
 > 
 > My recollection is that we shifted from "Enable the apic even if the 
 > BIOS disabled it" to "Only use the apic if the BIOS didn't disable it" 
 > around that time, which meant that distributions could actually turn on 
 > apic-on-up support without breaking everything. That might correspond to 
 > what you're seeing.

If memory serves correctly, that was circa 2.6.10, back in these commits..

commit a068ea13d1db406e15c346e93530343f6e70184c
Author: Len Brown <len.brown@...el.com>
Date:   Sun Oct 10 05:21:08 2004 -0400

    [ACPI] If BIOS disabled the LAPIC, believe it by default.
    "lapic" is available to force enabling the LAPIC
    in the event you know more than your BIOS vendor.
    http://bugzilla.kernel.org/show_bug.cgi?id=3238

commit 2fcfece90db9643b6f30a7ad343898a2871e6a81
Author: Len Brown <len.brown@...el.com>
Date:   Sat Oct 9 20:12:45 2004 -0400

    [ACPI] Don't enable LAPIC when the BIOS disabled it.
    Doing so apparently breaks every Dell on Earth.
    http://bugzilla.kernel.org/show_bug.cgi?id=3238


But those changes relate to the local APIC, which 'noapic' shouldn't
have any effect on should it ?

	Dave

-- 
http://www.codemonkey.org.uk
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