linux-kernel - Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

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Message-ID: <20080129064724.0f7e91e5@laptopd505.fenrus.org>
Date:	Tue, 29 Jan 2008 06:47:24 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	tcamuso@...hat.com
Cc:	Greg KH <greg@...ah.com>, Matthew Wilcox <matthew@....cx>,
	Grant Grundler <grundler@...isc-linux.org>,
	Loic Prylli <loic@...i.com>, Adrian Bunk <bunk@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	Jeff Garzik <jeff@...zik.org>,
	linux-pci@...ey.karlin.mff.cuni.cz, Martin Mares <mj@....cz>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver
 opt-in

On Tue, 29 Jan 2008 09:15:02 -0500
Tony Camuso <tcamuso@...hat.com> wrote:

> Greg KH wrote:
> > On Mon, Jan 28, 2008 at 08:18:04PM -0700, Matthew Wilcox wrote:
> >> I'm more optimistic because we've so severely restricted the use of
> >> mmconf after these patches that it's unlikely to cause problems.
> >> I also hear Vista is now using mmconf, so fewer implementations
> >> are going to be buggy at this point.
> > 
> > Hahahaha, oh, that's a good one...
> > 
> > But what about the thousands of implementations out there that are
> > buggy?
> > 
> > I'm with Arjan here, I'm very skeptical.
> > 
> > Matthew, with Arjan's patch, is anything that currently works now
> > broken?  Why do you feel it is somehow "wrong"?
> > 
> > thanks,
> > 
> > greg k-h
> 
> Greg,
> 
> The problem with Arjan's patch, if I understand it correctly, is that
> it requires drivers to make a call to access extended PCI config
> space.
> 
> And, IIRC, Arjan's patch encumbers drivers for all arch's, even those
> that have no MMCONFIG problems.
> 
> The patches proposed by Loic, Ivan, Matthew, and myself, all address
> the problem in an x86-specific manner that is transparent to the
> drivers.

this is not quite correct; the patches from Loic, Ivan, Matthew and you are for a different
problem statement.

Your patch problem statement is "need to fix mmconfig", my patch problem statement is "need
to not make users who don't need it suffer". These are orthogonal problems.


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