From: ebiederm@xmission.com (Eric W. Biederman)
Subject: Re: [discuss] Re: 2.6.19-rc4: known unfixed regressions
	(v3)
Date: Wed, 08 Nov 2006 10:38:27 -0700
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Cc: Andrew Morton <akpm@osdl.org>, len.brown@intel.com,
   Thierry Vignaud <tvignaud@mandriva.com>, Matthew Wilcox <matthew@wil.cx>,
   Ernst Herzberg <earny@net4u.de>, Aaron Durbin <adurbin@google.com>,
   Alex Romosan <romosan@sycorax.lbl.gov>, openib-general@openib.org,
   Andi Kleen <ak@suse.de>, linux-ide@vger.kernel.org,
   oprofile-list@lists.sourceforge.net, Jens Axboe <jens.axboe@oracle.com>,
   Adrian Bunk <bunk@stusta.de>, linux-pci@atrey.karlin.mff.cuni.cz,
   Elimar Riesebieter <riesebie@lxtec.de>, discuss@x86-64.org,
   linux-pm@osdl.org, Komuro <komurojun-mbn@nifty.com>,
   Jeff Chua <jeff.chua.linux@gmail.com>,
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   neilb@cse.unsw.edu.au,
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To: Linus Torvalds <torvalds@osdl.org>
In-Reply-To: <Pine.LNX.4.64.0611080803280.3667@g5.osdl.org> (Linus Torvalds's
	message of "Wed, 8 Nov 2006 08:05:18 -0800 (PST)")
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Linus Torvalds <torvalds@osdl.org> writes:

> On Wed, 8 Nov 2006, Matthew Wilcox wrote:
>>
>> On Wed, Nov 08, 2006 at 08:39:44AM +0100, Andi Kleen wrote:
>> > ACPI knows the number of busses.
>> =

>> But what if the number of busses increases later, eg by hotplugging
>> a card with a PCI-PCI bridge on it?  Or does it know the number of
>> busses which can be supported by this machine's MMCONFIG region?
>
> ACPI will give the maximum number.
>
> However, in this case, the correct thing to do (always _has_ been) is to =

> not use ACPI for _anything_, but just read the base and the size of the =

> MMCONFIG region from the hardware itself.
>
> Anyway, I do not consider this a regression. MMCONFIG has _never_ worked =

> reliably. It has always been a case of "we can make it work on some =

> machines by making it break on others".

The implementations I have seen, I believe have all been on bridges and
the maximum size is actually generated from the bus number below the bridge.

Eric