--- /dev/null
+From 1a4b1a41b8a3d5256019854e851beed063b34344 Mon Sep 17 00:00:00 2001
+From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+Date: Tue, 13 Sep 2011 15:16:33 -0300
+Subject: pci: Don't crash when reading mpss from root complex
+
+From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+
+commit 1a4b1a41b8a3d5256019854e851beed063b34344 upstream.
+
+In pcie_find_smpss(), we have the following statement:
+
+ if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
+ dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))
+
+The problem is that at least on my machine, this gets called for the
+root complex (virtual P2P bridge), and dev->bus->self is NULL since
+the parent bus for this is not itself anchor to a PCI device.
+
+This adds the necessary NULL check.
+
+Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+Acked-by: Jon Mason <mason@myri.com>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
+
+---
+ drivers/pci/probe.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+--- a/drivers/pci/probe.c
++++ b/drivers/pci/probe.c
+@@ -1352,7 +1352,8 @@ static int pcie_find_smpss(struct pci_de
+ * will occur as normal.
+ */
+ if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
+- dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))
++ (dev->bus->self &&
++ dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT)))
+ *smpss = 0;
+
+ if (*smpss > dev->pcie_mpss)