Re: PCI warning on boot 3.8.0-rc1

[Alex Williamson <alex.williamson@redhat.com>]

On Mon, 2013-02-04 at 10:36 -0800, Stephen Hemminger wrote:
> > I think drivers/pci/search.c is identical between 3.7 and 3.8-rc1.  Is
> > this the first time you've turned on the IOMMU on that box?
> 
> It exists in 3.7 and earlier kernels, just haven't turned on same config.
> 
> > It's the same warning as in this bugzilla:
> > https://bugzilla.kernel.org/show_bug.cgi?id=44881, and there's a patch
> > there at https://bugzilla.kernel.org/show_bug.cgi?id=44881#c11, but
> > it's just a quirk that turns off VT-d if we find certain broken
> > bridges.  It doesn't look like you have any of those (although I don't
> > know what you have at 05:00.0).
> > 
> > Bjorn
> 
> This is a standard ASUS motherboard, and don't want to disable VT-d.

Stephen,

Can you give the lspci -vvv of device 5:00.0 to see if it's one we've
seen before?  Does the patch below help?

Bjorn, I think we need to quirk it somehow.  So far they've all been
PCI-to-PCI bridges attached to root ports where we expect it's actually
a PCIe-to-PCI bridge.  Seems like maybe we could have the same attached
to a downstream port.  The patch below avoids the WARN and gives us a
device, but of course pci_is_pcie reports wrong for this device and may
cause some trickle down breakage.  A more complete option might be to
add a is_pcie flag to the device that can be set independent of
pcie_cap.  We'd need to check all the callers for assumptions, but then
we could put the quirk in one place and hopefully fix everything.
Thoughts?  Thanks,

Alex


diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index bf969ba..65ae270 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -42,6 +42,15 @@ pci_find_upstream_pcie_bridge(struct pci_dev *pdev)
 		}
 		/* PCI device should connect to a PCIe bridge */
 		if (pci_pcie_type(pdev) != PCI_EXP_TYPE_PCI_BRIDGE) {
+			/*
+			 * Not all PCIe-to-PCI bridges expose a PCIe
+			 * capability.  If we make it to a PCIe root port
+			 * and the previous device was a PCI-to-PCI bridge,
+			 * assume it was really a PCIe-to-PCI bridge.
+			 */
+			if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT &&
+			    tmp && tmp->hdr_type == PCI_HEADER_TYPE_BRIDGE)
+				return tmp;
 			/* Busted hardware? */
 			WARN_ON_ONCE(1);
 			return NULL;