linux-kernel - Re: Crash on reading the whole PCI config of PIIX4 SMBus

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Date:	Wed, 23 Sep 2009 16:15:18 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Henrik Kretzschmar <henne@...htwindheim.de>
Cc:	Wolfram Sang <w.sang@...gutronix.de>, jbarnes@...tuousgeek.org,
	linux-pci@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Crash on reading the whole PCI config of PIIX4 SMBus

On Wed, 23 Sep 2009 16:11:45 +0200, Henrik Kretzschmar wrote:
> Jean Delvare schrieb:
> > You might still want to check if maybe ACPI is interfering with the
> > i2c-piix4 driver. This isn't the kind of result I'd expect, but who
> > knows.
> >   
> This machine doesnt even have ACPI. :) Just APM.
> 
> But reading the config space may be dangerous, refering the manpage of lspci:
> "
>       -xxx   Show  hexadecimal  dump of the whole PCI configuration space. It
>               is available only to root as several PCI devices crash when  you
>               try to read some parts of the config space (this behavior proba-
>               bly doesnt violate the PCI standard, but  its  at  least  very
>               stupid).  However,  such  devices are rare, so you neednt worry
>               much.
> "
> 
> I seem to have stumbled over one of those stupidnesses.
> That is the reason why non-root users are only allowed to
> read the first 64 byte of the config space.

That's right, but it doesn't explain why i2c-piix4 crashes in the first
place, not why merely loading it causes further lspci -xxx to crash
when they did not beforehand. I admit I am totally clueless.

>  
> So its imho generally a good idea to run lspci -xxx on every machine you can
> and save some time searching in the wrong places.


-- 
Jean Delvare
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