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

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Message-Id: <200705231611.18944.jbarnes@virtuousgeek.org>
Date:	Wed, 23 May 2007 16:11:17 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	David Miller <davem@...emloft.net>
Cc:	torvalds@...ux-foundation.org, hancockr@...w.ca,
	galibert@...ox.com, linux-kernel@...r.kernel.org, ak@...e.de,
	cebbert@...hat.com, lenb@...nel.org
Subject: Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources

On Wednesday, May 23, 2007 4:04 pm David Miller wrote:
> From: Linus Torvalds <torvalds@...ux-foundation.org>
> Date: Wed, 23 May 2007 15:16:23 -0700 (PDT)
>
> > That crap should be seen for the crap it is! Dammit, how hard can
> > it be to just admit that mmconfig isn't that great?
>
> I knew mmconfig was broken conceptually the first time I started
> seeing write posting "bug fixes" for it that would do a read back
> from PCI config space via mmconfig to post the write, which of course
> has potential side-effects on the device and is absolutely illegal if
> the write just performed put the device into a PM state or whatever.

I've actually seen that specific form of posted write flushing cause 
crashes on some machines, so yes, it sucks.

Unfortunately, I don't think we have any other way of getting at 
extended config space on x86, unless EFI provides methods or something, 
but I'm not sure that would be an improvement...

Jesse
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