[RFC PATCH] iommu: Handle domain allocation failure gracefully

[Vasant Hegde <vasant.hegde@amd.com>]

Current code does not validate domain allocation failures. This will
result in random failure at later stage. Hence handle domain allocation
failures.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
Hi Joerg,
  With current code whenever amd driver failes to allocate domain we hit
  failure at late stage and it became difficult to debug. Hence I
  thought of adding this fix.

  I see that in commit 6e1aa2049154 you have intentionally didn't check
  the return value. Looking into drivers/iommu/* it looks like all
  drivers has domain_alloc() callback handler. But some drivers (like msm
  - msm_iommu_domain_alloc()) allocates default domain for certain type
  only. Hence I'm not sure whether its ok to handle domain allocation
  failures or not. Hence I have marked this patch as RFC.

  Let me know whether this patch is fine -OR- is there any other way we can
  handle domain allocation failures?

-Vasant

 drivers/iommu/iommu.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 780fb7071577..e8a1e7fbffb9 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -289,18 +289,21 @@ int iommu_probe_device(struct device *dev)
 
 	/*
 	 * Try to allocate a default domain - needs support from the
-	 * IOMMU driver. There are still some drivers which don't
-	 * support default domains, so the return value is not yet
-	 * checked.
+	 * IOMMU driver.
 	 */
 	mutex_lock(&group->mutex);
-	iommu_alloc_default_domain(group, dev);
+	ret = iommu_alloc_default_domain(group, dev);
+	if (ret) {
+		mutex_unlock(&group->mutex);
+		iommu_group_put(group);
+		goto err_release;
+	}
 
 	/*
 	 * If device joined an existing group which has been claimed, don't
 	 * attach the default domain.
 	 */
-	if (group->default_domain && !group->owner) {
+	if (!group->owner) {
 		ret = __iommu_attach_device(group->default_domain, dev);
 		if (ret) {
 			mutex_unlock(&group->mutex);
@@ -1665,7 +1668,7 @@ static int probe_get_default_domain_type(struct device *dev, void *data)
 	return 0;
 }
 
-static void probe_alloc_default_domain(struct bus_type *bus,
+static int probe_alloc_default_domain(struct bus_type *bus,
 				       struct iommu_group *group)
 {
 	struct __group_domain_type gtype;
@@ -1679,7 +1682,7 @@ static void probe_alloc_default_domain(struct bus_type *bus,
 	if (!gtype.type)
 		gtype.type = iommu_def_domain_type;
 
-	iommu_group_alloc_default_domain(bus, group, gtype.type);
+	return iommu_group_alloc_default_domain(bus, group, gtype.type);
 
 }
 
@@ -1753,11 +1756,10 @@ int bus_iommu_probe(struct bus_type *bus)
 		mutex_lock(&group->mutex);
 
 		/* Try to allocate default domain */
-		probe_alloc_default_domain(bus, group);
-
-		if (!group->default_domain) {
+		ret = probe_alloc_default_domain(bus, group);
+		if (ret) {
 			mutex_unlock(&group->mutex);
-			continue;
+			break;
 		}
 
 		iommu_group_create_direct_mappings(group);
-- 
2.31.1