[PATCH v5 10/17] iommu: Introduce iommu_group_mutex_assert()

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

Add function to check iommu group mutex lock. So that device drivers can
rely on group mutex lock instead of adding another driver level lock
before modifying driver specific device data structure.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
 drivers/iommu/iommu.c | 17 +++++++++++++++++
 include/linux/iommu.h |  5 +++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 502779d57b68..b27d98374d43 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1246,6 +1246,23 @@ void iommu_group_remove_device(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_group_remove_device);
 
+/**
+ * iommu_group_mutex_assert - Check device group mutex lock
+ * @dev: the device that has group param set
+ *
+ * This function is called by an iommu driver to check whether it holds
+ * group mutex lock for the given device or not.
+ *
+ * Note that this function must be called after device group param is set.
+ */
+void iommu_group_mutex_assert(struct device *dev)
+{
+	struct iommu_group *group = dev->iommu_group;
+
+	lockdep_assert_held(&group->mutex);
+}
+EXPORT_SYMBOL_GPL(iommu_group_mutex_assert);
+
 static struct device *iommu_group_first_dev(struct iommu_group *group)
 {
 	lockdep_assert_held(&group->mutex);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 7f6342bc71c3..c983b6a1ebce 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -751,6 +751,7 @@ extern int iommu_group_set_name(struct iommu_group *group, const char *name);
 extern int iommu_group_add_device(struct iommu_group *group,
 				  struct device *dev);
 extern void iommu_group_remove_device(struct device *dev);
+extern void iommu_group_mutex_assert(struct device *dev);
 extern int iommu_group_for_each_dev(struct iommu_group *group, void *data,
 				    int (*fn)(struct device *, void *));
 extern struct iommu_group *iommu_group_get(struct device *dev);
@@ -1144,6 +1145,10 @@ static inline void iommu_group_remove_device(struct device *dev)
 {
 }
 
+static inline void iommu_group_mutex_assert(struct device *dev)
+{
+}
+
 static inline int iommu_group_for_each_dev(struct iommu_group *group,
 					   void *data,
 					   int (*fn)(struct device *, void *))
-- 
2.31.1