iommu: Add iommu_copy_struct_from_full_user_array helper

The iommu_copy_struct_from_user_array helper can be used to copy a single
entry from a user array which might not be efficient if the array is big.

Add a new iommu_copy_struct_from_full_user_array to copy the entire user
array at once. Update the existing iommu_copy_struct_from_user_array kdoc
accordingly.

Link: https://patch.msgid.link/r/5cd773d9c26920c5807d232b21d415ea79172e49.1730836308.git.nicolinc@nvidia.com
Reviewed-by: Kevin Tian <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Nicolin Chen <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

include/linux/iommu.h

@@ -493,14 +493,60 @@ static inline int __iommu_copy_struct_from_user_array(
  * @index: Index to the location in the array to copy user data from
  * @min_last: The last member of the data structure @kdst points in the
  *            initial version.
- * Return 0 for success, otherwise -error.
+ *
+ * Copy a single entry from a user array. Return 0 for success, otherwise
+ * -error.
  */
 #define iommu_copy_struct_from_user_array(kdst, user_array, data_type, index, \
 					  min_last)                           \
 	__iommu_copy_struct_from_user_array(                                  \
 		kdst, user_array, data_type, index, sizeof(*(kdst)),          \
 		offsetofend(typeof(*(kdst)), min_last))
 
+/**
+ * iommu_copy_struct_from_full_user_array - Copy iommu driver specific user
+ *         space data from an iommu_user_data_array
+ * @kdst: Pointer to an iommu driver specific user data that is defined in
+ *        include/uapi/linux/iommufd.h
+ * @kdst_entry_size: sizeof(*kdst)
+ * @user_array: Pointer to a struct iommu_user_data_array for a user space
+ *              array
+ * @data_type: The data type of the @kdst. Must match with @user_array->type
+ *
+ * Copy the entire user array. kdst must have room for kdst_entry_size *
+ * user_array->entry_num bytes. Return 0 for success, otherwise -error.
+ */
+static inline int
+iommu_copy_struct_from_full_user_array(void *kdst, size_t kdst_entry_size,
+				       struct iommu_user_data_array *user_array,
+				       unsigned int data_type)
+{
+	unsigned int i;
+	int ret;
+
+	if (user_array->type != data_type)
+		return -EINVAL;
+	if (!user_array->entry_num)
+		return -EINVAL;
+	if (likely(user_array->entry_len == kdst_entry_size)) {
+		if (copy_from_user(kdst, user_array->uptr,
+				   user_array->entry_num *
+					   user_array->entry_len))
+			return -EFAULT;
+	}
+
+	/* Copy item by item */
+	for (i = 0; i != user_array->entry_num; i++) {
+		ret = copy_struct_from_user(
+			kdst + kdst_entry_size * i, kdst_entry_size,
+			user_array->uptr + user_array->entry_len * i,
+			user_array->entry_len);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
 /**
  * struct iommu_ops - iommu ops and capabilities
  * @capable: check capability