From: AMEET M. PARANJAPE <aparanja@redhat.com>
Date: Tue, 13 Jan 2009 10:24:13 -0600
Subject: [ppc64] handle null iommu dma-window property correctly
Message-id: 496CC02D.8000708@REDHAT.COM
O-Subject: Re: [PATCH RHEL5.4 BZ393241] Handle null iommu dma-window property correctly
Bugzilla: 393241
RH-Acked-by: David Howells <dhowells@redhat.com>

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=393241

Description:
===========
Some versions of pSeries firmware fail to set up
a dma-window property for PCI slots that are occupied
with bad hardware.

As a result, the loop searching for this property, in
iommu_dev_setup_pSeriesLP(), can run to the end, resulting
in a NULL pointer dereference later in the routine. This
patch prevents the crash, and prints a warning message.

RHEL Version Found:
================
RHEL 5.3

kABI Status:
============
No symbols were harmed.

Brew:
=====
Built on all platforms.
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1641732

Upstream Status:
================
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=650f7b3b2f0ead0673e90452cf3dedde97c537ba

Test Status:
============
Boot the kernel on a System P box with a known bad card and the boot fails.
Now with this patch applied this failure is not seen as the kernel boots
without a crash.
===============================================================
Ameet Paranjape 978-392-3903 ext 23903
IBM on-site partner

Proposed Patch:
===============

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index d3bcb66..02fdeaa 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -520,6 +520,14 @@ static void iommu_dev_setup_pSeriesLP(struct pci_dev *dev)
 			break;
 	}
 
+	if (!pdn || !PCI_DN(pdn)) {
+		printk(KERN_WARNING "pci_dma_dev_setup_pSeriesLP: "
+		       "no DMA window found for pci dev=%s dn=%s\n",
+				 pci_name(dev), dn? dn->full_name : "<null>");
+		return;
+	}
+	DBG("  parent is %s\n", pdn->full_name);
+
 	/* Check for parent == NULL so we don't try to setup the empty EADS
 	 * slots on POWER4 machines.
 	 */