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

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Message-ID: <476D1D16.5090703@garzik.org>
Date:	Sat, 22 Dec 2007 09:20:06 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	linux-kernel@...r.kernel.org, gregkh@...e.de,
	linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: [patch] Make MMCONFIG space (extended PCI config space) a driver
 opt-in issue

Arjan van de Ven wrote:
> Hi,
> 
> Linus really wants the extended (4Kb) PCI configuration space (using MCFG acpi table etc) to be opt-in, since there's many issues with it and most drivers don't even use/need it. The idea behind opt-in is that if you don't use it, you don't get to suffer the bugs...
> 
> Booted on my 64 bit test machine; sadly it has a defunct BIOS that doesn't have a working MCFG.
> 
> 
> From: Arjan van de Ven <arjan@...ux.intel.com>
> Subject: Make MMCONFIG space a driver opt-in
> 
> There are many issues with using the extended PCI configuration space 
> (CPU, Chipset and most of all BIOS bugs). This while the vast majority of drivers
> and devices don't even use/need to use the memory mapped access methods since they
> don't use the config space beyond the traditional 256 bytes.
> 
> This patch makes accessing the extended config space a driver choice, via the
> 
> pci_enable_ext_config(pdev)

Yuck.  And, Linus is just being silly.  Wait a year then turn on 
MMCONFIG :)  It took PCI MSI a while to mature, but is finally getting 
there.

	Jeff





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