linux-kernel - Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch

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Date:	Tue, 30 Oct 2007 15:38:01 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
cc:	Arjan van de Ven <arjan@...radead.org>,
	Robert Hancock <hancockr@...w.ca>, Greg KH <greg@...ah.com>,
	akpm@...ux-foundation.org, ak@...e.de, rajesh.shah@...el.com,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch

On Tue, 30 Oct 2007, Linus Torvalds wrote:
>
> No. You really don't see the big picture. There's been tons of problems 
> with MMCONFIG. Like the fact that other devices have their IO regions 
> registered on top of it, because the MMCONFIG thing was done as a hidden 
> resource. Or the fact that the area claimed was too small. Or too large. 
> Or not listed at all.

Actually, I guess the bad case wasn't "not listed at all", but incorrectly 
listed - so the probing would go to the wrong address, not find any 
devices, and then promptly result in an unusable machine with no hardware 
attached.

I _think_ (and hope) those machines were never released. But even now, on 
my main machine, I get "MCFG area at f0000000 is not E820-reserved", and 
probably the only reason the PCI layer doesn't overwrite it is because it 
does show up as a PnP region, and I have pnp support enabled.

Basically, the resource allocation for mmconf has always been broken 
(largely by *design* by Intel!). And by being broken, it has been 
unreliable.

			Linus
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