linux-kernel - Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources

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Date:	Wed, 23 May 2007 15:48:19 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Olivier Galibert <galibert@...ox.com>
cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Robert Hancock <hancockr@...w.ca>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>, Chuck Ebbert <cebbert@...hat.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard
 resources

On Thu, 24 May 2007, Olivier Galibert wrote:
> 
> Isn't that a mac-intel instant killer?  AFAIK they don't have type1,
> period.

mac-intel are totally standard Intel chipsets. They have all of 
conf1/conf2/mmconfig afaik.

I just happily booted my mac-mini with "pci=nommconf", nothing bad 
happened, and the kernel says

	PCI: Using configuration type 1

and I don't think you even _can_ disable conf1 type accesses: they are 
deep in the Intel chipsets.

Of course, in a virtualized environment, anything can happen. Virtual 
machines prefer mmconf, because you can use page-level remapping to hide 
devices or make pseudo-devices show up by mapping in pages that have 
nothing to do with the true hardware.

So no, I don't think Alan was totally smoking crack when he talked about 
"trusted" computing. Read the above paragraph a few times. (You can do it 
with trapping IO port accesses too, but it's going to cost you a lot, so 
if you want to make a fast but untrustoworthy setup, MMIO is the better 
option).

		Linus
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