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

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Message-id: <4773EBB4.2020805@shaw.ca>
Date:	Thu, 27 Dec 2007 12:15:16 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jeff Garzik <jeff@...zik.org>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, gregkh@...e.de,
	linux-pci <linux-pci@...ey.karlin.mff.cuni.cz>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Mares <mj@....cz>, Matthew Wilcox <matthew@....cx>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver
 opt-in

Linus Torvalds wrote:
> 
> On Thu, 27 Dec 2007, Jeff Garzik wrote:
>> 2) [non-minor] hmmmm.
>>
>> 	[jgarzik@...e ~]$ lspci -n | wc -l
>> 	23
>>
>> So I would have to perform 23 sysfs twiddles, before I could obtain a full and
>> unabridged 'lspci -vvvxxx'?
> 
> Or you force it on with "pci=mmconfig" or something at boot-time.
> 
> But yes. The *fact* is that MMCONFIG has not just been globally broken, 
> but broken on a per-device basis. I don't know why (and quite frankly, I 
> doubt anybody does), but the PCI device ID corruption happened only for a 
> specific set of devices.
> 
> Whether it was a timing issue with particular devices or whether it was a 
> timing issue with some particular bridge (and could affect any devices 
> behind that bridge), who knows... It almost certainly was brought on by a 
> borderline (or broken) northbridge, but it apparently only affected 
> specific devices - which makes me suspect that it wasn't *entirely* due to 
> just the northbridge, and it was a combination of things.

Pointer to such a report? The only single-device problems I'm aware of
are with some devices within the K8 integrated northbridge, which we
already handle. Other than that, the only non-global problems I'm aware
of are devices behind host bridges which can't receive/handle MMCONFIG
requests, in which case the problem would be bus-wide.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/



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