linux-kernel - Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

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Date:	Fri, 11 Jan 2008 12:27:06 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Matthew Wilcox <matthew@....cx>
cc:	Greg KH <gregkh@...e.de>, Arjan van de Ven <arjan@...radead.org>,
	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	Jeff Garzik <jeff@...zik.org>,
	linux-pci@...ey.karlin.mff.cuni.cz,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Mares <mj@....cz>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver
 opt-in

On Fri, 11 Jan 2008, Matthew Wilcox wrote:
> 
> Ivan's patch doesn't start enabling MMCONFIG in more places than we
> currently do.  It makes us use conf1 accesses for all accesses below
> 256 bytes.  That fixes all known problems to date.

.. and I agree with that patch. But there will be people who try to access 
extended space by mistake, and they'll have a hard-locked machine or 
something.

> > Tell me what *other* armor plating you could have that actually works?
> 
> The armour plating that already exists -- pci=nommconf.

No. It needs to be automatic, OR THE OTHER WAY AROUND.

Ie we disable the unsafe feature on purpose, and then force people who 
access it to do so *consciously*.

Extended config space is different, for chissake! It's not even like it's 
just a bigger normal config space where normal config accesses just 
overflow into it. It really does have different rules etc.

			Linus
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