linux-kernel - Re: [PATCH 0/5]PCI: x86 MMCONFIG

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Date:	Wed, 19 Dec 2007 15:16:09 -0800
From:	Greg KH <gregkh@...e.de>
To:	tcamuso@...hat.com
Cc:	linux-kernel@...r.kernel.org, linux-pci@...ey.karlin.mff.cuni.cz,
	prarit@...hat.com
Subject: Re: [PATCH 0/5]PCI: x86 MMCONFIG

On Wed, Dec 19, 2007 at 05:17:46PM -0500, tcamuso@...hat.com wrote:
> OVERVIEW
> =======
> 
> The patches should be applied in sequence to obviate any
> possible build problems.
> 
> The patch-set was built against 2.6.24-rc5
> 
> Description
> ===========
> 
> There exist devices that do not respond correctly to PCI
> MMCONFIG accesses in x86 platforms.

What devices are these?  Do you have reports of them somewhere?

> This patch-set detects the problem by comparing an MMCONFIG
> read to a Legacy PCI config read of the vendor/device dword
> of every device discovered during the PCI probing sequence.
> 
> A miscompare means that a device does not correctly respond
> to MMCONFIG accesses. When the patch code detects this condition,
> the bus that serves this device, and all subordinate buses, will
> be programmed to use Legacy PCI Config accesses.
> 
> This patch-set DOES NOT detect devices that generate machine
> checks against MMCONFIG accesses. For such systems,
> "pci=nommconf" is required in the boot command.

That sounds like this patchset can cause bad side affects on hardware
that currently works just fine.  That is not a good thing to be adding
to the kernel, right?

thanks,

greg k-h
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