linux-kernel - Re: [discuss] Re: 2.6.19-rc4: known unfixed regressions (v3)

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Date:	Wed, 8 Nov 2006 18:26:50 +0100
From:	Adrian Bunk <bunk@...sta.de>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	Matthew Wilcox <matthew@....cx>, Andi Kleen <ak@...e.de>,
	Jeff Chua <jeff.chua.linux@...il.com>,
	Aaron Durbin <adurbin@...gle.com>,
	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	gregkh@...e.de, linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: [discuss] Re: 2.6.19-rc4: known unfixed regressions (v3)

On Wed, Nov 08, 2006 at 08:05:18AM -0800, Linus Torvalds wrote:
> 
> 
> 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".

It is a serious regression:

The problem is that with the default CONFIG_PCI_GOANY, MMCONFIG is the 
_first_ method tried.

In practice, this implies that nearly every system possibly affected 
will suffer from a MMCONFIG breakage like the one Jeff observed...

> 			Linus

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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