On Tue, 2013-06-25 at 22:20 -0600, Bjorn Helgaas wrote:
> On Thu, Jun 20, 2013 at 10:15 AM, Joerg Roedel <joro@xxxxxxxxxx> wrote:
> > On Thu, Jun 20, 2013 at 09:44:51AM -0600, Alex Williamson wrote:
> >> On Thu, 2013-06-20 at 15:59 +0200, Joerg Roedel wrote:
> >> > On Tue, May 28, 2013 at 12:40:20PM -0600, Alex Williamson wrote:
> >> > > + if (!pci_is_root_bus(pdev->bus)) {
> >> > > + struct pci_dev *parent = pdev->bus->self;
> >> > > +
> >> > > + if (pci_is_pcie(parent) &&
> >> > > + pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
> >> > > + return true;
> >> > > + }
> >> >
> >> > Hmm, that looks a bit dangerous.
> >>
> >> How so? The algorithm seems pretty simple and logical.
> >
> > It is simple, but it is still a heuristic that may fail at some point,
> > no?
> >
> >> Actually, I believe Bjorn rejected the idea of a fixed list because this
> >> problem is detectable. He also doesn't want me messing with quirks to
> >> pci_is_pcie() in PCI because he wants a 1:1 relation between that and
> >> having a PCIe capability. So, I'm stuck and this is where it's ended
> >> up. Thanks,
> >
> > I think implementing such a list is much safer.
> >
> > Bjorn, why didn't you like that idea?
>
> Sorry, I can't remember, and I haven't been able to find the
> discussion where I said that. I think the current patches are all in
> drivers/iommu, and if a list makes sense there, it's fine with me.
Here's the comment I remember
https://bugzilla.kernel.org/show_bug.cgi?id=44881#c7
Comment #7 From Bjorn Helgaas 2012-08-23 15:58:39
[snip]
I doubt the upstream device is at fault. More likely the
downstream device is really a PCIe device (a PCIe-to-PCI bridge)
but just fails to report a PCIe capability. I think this
situation is likely too common to deal with via quirks, so we'll
have to figure out a way to just make this work.
Thanks,
Alex
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