linux-kernel - Re: 3.6-rc7 boot crash + bisection

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Date:	Wed, 26 Sep 2012 15:20:50 +0200
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	Florian Dazinger <florian@...inger.net>,
	<linux-kernel@...r.kernel.org>,
	iommu <iommu@...ts.linux-foundation.org>
Subject: Re: 3.6-rc7 boot crash + bisection

On Tue, Sep 25, 2012 at 01:43:46PM -0600, Alex Williamson wrote:
> Joerg, any thoughts on a quirk for this?  Unfortunately we can't just
> skip IOMMU groups when an alias is broken because it puts the other
> IOMMU groups at risk that might not actually be isolated from this
> device.  It looks like we parse the alias info before PCI is probed, so
> maybe we'd need to call the quirk from iommu_init_device itself.

I fear that the BIOS does everything right and device 08:04.0 is indeed
using 08:00.0 as request-id. There are a couple of devices where this
happens, usually when the vendor just took the old 32bit PCI chip, added
a transparent PCIe-to-PCI bridge to the device and sell it a PCIe.

So the assumption that every request-id has a corresponding pci_dev
structure does not hold. I also had made that assumption in the
AMD IOMMU driver but had to add code which removes that assumption. We
should look for a way to remove that assumption from the group-code too.

	Joerg

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