Re: [Fwd: Re: [PATCH 0/5]PCI: x86 MMCONFIG]

From: Robert Hancock
Date: Thu Dec 20 2007 - 19:44:46 EST


Tony Camuso wrote:
Greg KH wrote:

Sure, I realize this, but it solves the problem in one way for broken
hardware, such that it at least allows it to work, right? It also
provides a better incentive for the manufacturer to fix their bios,
which as you are on-site at HP, it would seem odd that they would just
not do that instead of trying to work around this in the kernel...

thanks,

greg k-h

I don't think that many OEMs have that much control over the BIOS in
their "value lines".
:)

And the MMCONFIG problem with enterprise systems and workstations, where
we do control the BIOS (for the most part), is due to known bugs in
certain versions of certain chipsets, HT1000, AMD8132, among them, not
the BIOS.

Anyway, we are devising better ways to deal with these anomalies
than blacklists and telling customers to use "pci=nommconf"

And we're bringing them to the community for discussion, improvement,
and, we hope, acceptance.

First off, I would like to see confirmation from the horses's mouths here (namely AMD, ServerWorks/Broadcom, and whoever else) that there is no other way to get around this problem than disabling MMCONFIG for accesses behind those chips.

The case of the device built into the K8 northbridge that's unreachable by MMCONFIG kind of makes sense, since the northbridge is what's translating the MMCONFIG memory access into config accesses. It seems bizarre to me that a bridge chip could possibly have such a problem. The MMCONFIG access should get translated into a configuration space access in the northbridge and from that point on there's no difference between an MMCONFIG and type1 access.

Look at MSI for another example, we recently had a patch from NVIDIA posted to enable Hypertransport MSI mapping bits on some chipsets so that MSI would function, because the BIOS failed to set them up properly. Are we sure there's not a similar BIOS configuration issue that could ideally be fixed in the BIOS, or else fixed up in the kernel?

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

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