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

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Message-Id: <200705221756.45221.jbarnes@virtuousgeek.org>
Date:	Tue, 22 May 2007 17:56:44 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Robert Hancock <hancockr@...w.ca>
Cc:	Olivier Galibert <galibert@...ox.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>, Chuck Ebbert <cebbert@...hat.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources

On Tuesday, May 22, 2007, Robert Hancock wrote:
> Jesse Barnes wrote:
> > On Tuesday, May 22, 2007, Robert Hancock wrote:
> >> Eww. I don't see where we disable the decode at all while we probe
> >> the BARs on the device. That seems like a bad thing, especially with
> >> the way we probe 64-bit BARs (do the low 32 bits first and then the
> >> high 32 bits). This means the base address effectively gets set to
> >> 0xfffffff0 momentarily, which might cause some issues.
> >
> > I'm a bit shocked that things work as well as they do without the
> > disabling...
> >
> >> I'd try adding some code inside pci_setup_device
> >> (drivers/pci/probe.c) to disable PCI_COMMAND_IO and
> >> PCI_COMMAND_MEMORY on the device when probing devices with the
> >> standard header type and then restoring the previous command bits
> >> afterwards, and see what effect that has. It'll be interesting if it
> >> does, since obviously it seems to work as it is with non-MMCONFIG
> >> access methods. Maybe the base address being set like that interferes
> >> with MMCONFIG access itself somehow?
> >
> > I tried that, and it seems to get past probing the graphics device at
> > least, but it hangs a bit later.  It could be that the enable/disable
> > I added wasn't correct though, I didn't check to see which one I
> > should disable in the command word, which may be a problem (just
> > disabled them both every probe).  I'll try again with more precise
> > enable/disable semantics.
>
> It'd be interesting to see at what access it ran into trouble next, at
> least if it's consistent. Could be that some device doesn't like having
> the decode disabled..

I think it actually gets through the probing but hangs elsewhere, but I'll 
have to test again to be sure.

Jesse
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