vfio: Type1 IOMMU implementation

This VFIO IOMMU backend is designed primarily for AMD-Vi and Intel
VT-d hardware, but is potentially usable by anything supporting
similar mapping functionality.  We arbitrarily call this a Type1
backend for lack of a better name.  This backend has no IOVA
or host memory mapping restrictions for the user and is optimized
for relatively static mappings.  Mapped areas are pinned into system
memory.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio.c

@@ -1376,6 +1376,13 @@ static int __init vfio_init(void)
 
 	pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
 
+	/*
+	 * Attempt to load known iommu-drivers.  This gives us a working
+	 * environment without the user needing to explicitly load iommu
+	 * drivers.
+	 */
+	request_module_nowait("vfio_iommu_type1");
+
 	return 0;
 
 err_groups_cdev: