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

Linus Torvalds
2007-05-23T22:50:10Z

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