[PATCH v2] iommu: Check dev->iommu in iommu_dev_xxx functions

[Shameer Kolothum]

The device iommu probe/attach might have failed leaving dev->iommu
to NULL and device drivers may still invoke these functions resulting
in a crash in iommu vendor driver code. Hence make sure we check that.

Also added iommu_ops to the "struct dev_iommu" and set it if the dev
is successfully associated with an iommu. 

Fixes: a3a195929d40 ("iommu: Add APIs for multiple domains per device")
Signed-off-by: Shameer Kolothum <shameerali.kolothum.th...@huawei.com>
---
v1 --> v2:
 -Added iommu_ops to struct dev_iommu based on the discussion with Robin.
 -Rebased against iommu-tree core branch.
---
 drivers/iommu/iommu.c | 19 +++++++------------
 include/linux/iommu.h |  2 ++
 2 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index fd76e2f579fe..6023d0b7c542 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -217,6 +217,7 @@ static int __iommu_probe_device(struct device *dev, struct 
list_head *group_list
        }
 
        dev->iommu->iommu_dev = iommu_dev;
+       dev->iommu->ops = iommu_dev->ops;
 
        group = iommu_group_get_for_dev(dev);
        if (IS_ERR(group)) {
@@ -2865,10 +2866,8 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);
  */
 int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features feat)
 {
-       const struct iommu_ops *ops = dev->bus->iommu_ops;
-
-       if (ops && ops->dev_enable_feat)
-               return ops->dev_enable_feat(dev, feat);
+       if (dev->iommu && dev->iommu->ops->dev_enable_feat)
+               return dev->iommu->ops->dev_enable_feat(dev, feat);
 
        return -ENODEV;
 }
@@ -2881,10 +2880,8 @@ EXPORT_SYMBOL_GPL(iommu_dev_enable_feature);
  */
 int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features feat)
 {
-       const struct iommu_ops *ops = dev->bus->iommu_ops;
-
-       if (ops && ops->dev_disable_feat)
-               return ops->dev_disable_feat(dev, feat);
+       if (dev->iommu && dev->iommu->ops->dev_disable_feat)
+               return dev->iommu->ops->dev_disable_feat(dev, feat);
 
        return -EBUSY;
 }
@@ -2892,10 +2889,8 @@ EXPORT_SYMBOL_GPL(iommu_dev_disable_feature);
 
 bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features 
feat)
 {
-       const struct iommu_ops *ops = dev->bus->iommu_ops;
-
-       if (ops && ops->dev_feat_enabled)
-               return ops->dev_feat_enabled(dev, feat);
+       if (dev->iommu && dev->iommu->ops->dev_feat_enabled)
+               return dev->iommu->ops->dev_feat_enabled(dev, feat);
 
        return false;
 }
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 524ffc2ff64f..ff0c76bdfb67 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -354,6 +354,7 @@ struct iommu_fault_param {
  * @fault_param: IOMMU detected device fault reporting data
  * @fwspec:     IOMMU fwspec data
  * @iommu_dev:  IOMMU device this device is linked to
+ * @ops:        iommu-ops for talking to the iommu_dev
  * @priv:       IOMMU Driver private data
  *
  * TODO: migrate other per device data pointers under iommu_dev_data, e.g.
@@ -364,6 +365,7 @@ struct dev_iommu {
        struct iommu_fault_param        *fault_param;
        struct iommu_fwspec             *fwspec;
        struct iommu_device             *iommu_dev;
+       const struct iommu_ops          *ops;
        void                            *priv;
 };
 
-- 
2.17.1