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 <jgg@nvidia.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240205115615.6053-10-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d14413916f93a0..8309e634977e2a 100644
--- a/drivers/iommu/iommu.c
+++ b/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);