iommu: Introduce iommu_group_mutex_assert()

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 <[email protected]>
Signed-off-by: Vasant Hegde <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: hegdevasant

drivers/iommu/iommu.c

@@ -1248,6 +1248,25 @@ void iommu_group_remove_device(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_group_remove_device);
 
+#if IS_ENABLED(CONFIG_LOCKDEP) && IS_ENABLED(CONFIG_IOMMU_API)
+/**
+ * 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);
+#endif
+
 static struct device *iommu_group_first_dev(struct iommu_group *group)
 {
 	lockdep_assert_held(&group->mutex);

include/linux/iommu.h

@@ -1356,6 +1356,14 @@ static inline ioasid_t iommu_alloc_global_pasid(struct device *dev)
 static inline void iommu_free_global_pasid(ioasid_t pasid) {}
 #endif /* CONFIG_IOMMU_API */
 
+#if IS_ENABLED(CONFIG_LOCKDEP) && IS_ENABLED(CONFIG_IOMMU_API)
+void iommu_group_mutex_assert(struct device *dev);
+#else
+static inline void iommu_group_mutex_assert(struct device *dev)
+{
+}
+#endif
+
 /**
  * iommu_map_sgtable - Map the given buffer to the IOMMU domain
  * @domain:	The IOMMU domain to perform the mapping