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

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Date:	Wed, 26 Sep 2012 08:35:59 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	"Roedel, Joerg" <Joerg.Roedel@....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 Wed, 2012-09-26 at 15:20 +0200, Roedel, Joerg wrote:
> 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.

Hmm, that throws a kink in iommu groups.  So perhaps we need to make an
alias interface to iommu groups.  Seems like this could just be an extra
parameter to iommu_group_get and iommu_group_add_device (empty in the
typical case).  Then we have the problem of what's the type for an
alias?  For AMI-Vi, it's a u16, but we need to be more generic than
that.  Maybe iommu groups should just treat it as a void* so iommus can
use a pointer to some structure or a fixed value like a u16 bus:slot.
Thoughts?  Thanks,

Alex

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