From: Andrew Morton <akpm@osdl.org>

Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 drivers/pci/msi.c |    3 +++
 1 file changed, 3 insertions(+)

diff -puN drivers/pci/msi-altix.c~msi-oops-workaround drivers/pci/msi-altix.c
diff -puN drivers/pci/msi.c~msi-oops-workaround drivers/pci/msi.c
--- a/drivers/pci/msi.c~msi-oops-workaround
+++ a/drivers/pci/msi.c
@@ -815,6 +815,9 @@ int pci_msi_supported(struct pci_dev * d
 	while (pdev->bus && pdev->bus->self)
 		pdev = pdev->bus->self;
 
+	if (!pdev->subordinate)
+		return -1;
+
 	/* check its bus flags */
 	if (pdev->subordinate->bus_flags & PCI_BUS_FLAGS_NO_MSI)
 		return -1;
_