powerpc/iommu: Don't detach device without IOMMU group

Some devices, for example PCI root port, don't have IOMMU table and
group. We needn't detach them from their IOMMU group. Otherwise, it
potentially incurs kernel crash because of referring NULL IOMMU group
as following backtrace indicates:

  .iommu_group_remove_device+0x74/0x1b0
  .iommu_bus_notifier+0x94/0xb4
  .notifier_call_chain+0x78/0xe8
  .__blocking_notifier_call_chain+0x7c/0xbc
  .blocking_notifier_call_chain+0x38/0x48
  .device_del+0x50/0x234
  .pci_remove_bus_device+0x88/0x138
  .pci_stop_and_remove_bus_device+0x2c/0x40
  .pcibios_remove_pci_devices+0xcc/0xfc
  .pcibios_remove_pci_devices+0x3c/0xfc

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index f58d8135aab2612297f1b95ffd7384ebf983e365..d773dd440a45a32560fed0176120709ff5ea860d 100644 (file)
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1144,6 +1144,17 @@ EXPORT_SYMBOL_GPL(iommu_add_device);
 
 void iommu_del_device(struct device *dev)
 {
+       /*
+        * Some devices might not have IOMMU table and group
+        * and we needn't detach them from the associated
+        * IOMMU groups
+        */
+       if (!dev->iommu_group) {
+               pr_debug("iommu_tce: skipping device %s with no tbl\n",
+                        dev_name(dev));
+               return;
+       }
+
        iommu_group_remove_device(dev);
 }
 EXPORT_SYMBOL_GPL(iommu_del_device);