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

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Date:	Fri, 11 Jan 2008 14:17:53 -0700
From:	Matthew Wilcox <matthew@....cx>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Greg KH <gregkh@...e.de>, Arjan van de Ven <arjan@...radead.org>,
	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	Jeff Garzik <jeff@...zik.org>,
	linux-pci@...ey.karlin.mff.cuni.cz,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Mares <mj@....cz>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

On Fri, Jan 11, 2008 at 01:12:12PM -0800, Linus Torvalds wrote:
> 
> 
> On Fri, 11 Jan 2008, Matthew Wilcox wrote:
> > 
> > But they can't.  We limit the size they can access to 256 bytes, unless
> > the kernel probed address 256 and it worked.
> 
> Umm. Probing address 256 (or *any* address) using MMCONFIG will simply 
> lock up the machine. HARD.

Did I miss a bug report?  The only problems I'm currently aware of are
the ones where using MMCONFIG during BAR probing causes a hard lockup on
some Intel machines, and the ones where we get bad config data on some
AMD machines due to the configuration retry status being mishandled.

All the other lockups I'm aware of are already handled by the existing
checks.

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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