x86_64: Calgary - Fix mis-handled PCI topology

Current code assumed that devices were directly connected to a Calgary
bridge, as it tried to get the iommu table directly from the parent bus
controller.

When we have another bridge between the Calgary/CalIOC2 bridge and the
device we should look upwards until we get to the top (Calgary/CalIOC2
bridge), where the iommu table resides.

Signed-off-by: Murillo Fernandes Bernardes <mfb@br.ibm.com>
Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 7 deletions

diff --git a/arch/x86_64/kernel/pci-calgary.c b/arch/x86_64/kernel/pci-calgary.c
index ba16c968ca3f..71da01e73f03 100644
--- a/arch/x86_64/kernel/pci-calgary.c
+++ b/arch/x86_64/kernel/pci-calgary.c
@@ -367,16 +367,15 @@ static inline struct iommu_table *find_iommu_table(struct device *dev)
 
         pdev = to_pci_dev(dev);
 
-        /* is the device behind a bridge? */
-        if (unlikely(pdev->bus->parent))
-                pbus = pdev->bus->parent;
-        else
-                pbus = pdev->bus;
+        pbus = pdev->bus;
+
+        /* is the device behind a bridge? Look for the root bus */
+        while (pbus->parent)
+                pbus = pbus->parent;
 
         tbl = pci_iommu(pbus);
 
-        BUG_ON(pdev->bus->parent &&
-               (tbl->it_busno != pdev->bus->parent->number));
+        BUG_ON(tbl && (tbl->it_busno != pbus->number));
 
         return tbl;
 }