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

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To: Robert Hancock <hancockr@...>
Cc: Arjan van de Ven <arjan@...>, Greg KH <greg@...>, Jesse Barnes <jbarnes@...>, <akpm@...>, <ak@...>, <rajesh.shah@...>, linux-kernel <linux-kernel@...>
Date: Tuesday, October 30, 2007 - 7:59 pm

On Tue, 30 Oct 2007, Robert Hancock wrote:

Don't be silly. Exactly _BECAUSE_ we cannot trust the firmware, we have to 
use conf1 (which we can trust) to verify it and/or fix things up.

Also, there are several devices that don't show up in the MMCFG things, or 
just otherwise get it wrong.

So just take a look at arch/x86/pci/mmconfig-shared.c and look for 
"conf1".

Really. Damn, I'm nervous taking any MMCFG patches that has you as an 
author, if you aren't even aware of these kinds of fundamnetal issues. You 
probably read the standards about how things are "supposed" to work, and 
then just believed them?

Rule #1 in kernel programming: don't *ever* think that things actually 
work the way they are documented to work. The documentation is a starting 
point, nothing else. 

And please be defensive in programming. We *know* conf1 cycles work. The 
hardware has been extensively tested, and there are no firmware 
interactions. There is *zero* reasons to use MMCONF cycles for normal 
devices. Ergo: switching over to MMCONF when not needed is stupid and 
fragile.

			Linus
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Messages in current thread:
Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch, Linus Torvalds, (Tue Oct 30, 11:15 am)
Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch, Arjan van de Ven, (Tue Oct 30, 12:47 pm)
Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch, Linus Torvalds, (Tue Oct 30, 7:59 pm)
Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch, Arjan van de Ven, (Tue Oct 30, 7:52 pm)
Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch, Arjan van de Ven, (Tue Oct 30, 1:28 pm)
Re: pci-disable-decode-of-io-memory-during-bar-sizing.patch, Arjan van de Ven, (Thu Nov 1, 10:08 am)
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