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

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Date:	Mon, 24 Dec 2007 08:13:07 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	Loic Prylli <loic@...i.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, gregkh@...e.de,
	linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: [patch] Make MMCONFIG space (extended PCI config space) a
	driver opt-in issue

> Are you prepared to guarantee that freely mixing mmconfig and type1 
> config accesses at runtime will always work, on all chipsets?  I'm 
> talking about silicon here, not kernel software.

We spinlock config space accesses. So the silicon will never see
simultaneous accesses, which is what I strongly suspect would be broken
in chipsets (asking for livelocks here).

Now there is the question of whether the silicon implements MMCONFIG
writes in some asynchronous way, in which case, there might be an issue
if you go bang the port right away but I very much doubt it.

Ben.

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