Request Device Assignment without IOMMU support
===============================================

WARNING: it is not secure to assign a device without IOMMU protection. A
domU can program the device to do DMA on its behalf, gaining access to
the whole system. Another security measure should be employed, such as
programming a MPU.


This document assumes one of the following:

- the IOMMU is absent from the system

- the IOMMU is disabled, e.g. status = "disabled" under the smmu node in
  device tree

- the device to be assigned is not protected by the IOMMU, e.g. no
  iommus property is present for the device in device tree


To assign the device to a dom0less domU anyway, follow these steps:

1) Add the usual xen,reg and xen,path property to the domU DTB snippet:

    ethernet: ethernet@ff0e0000 {
        compatible = "cdns,zynqmp-gem";
        xen,path = "/amba/ethernet@ff0e0000";
        xen,reg = <0x0 0xff0e0000 0x1000 0x0 0xff0e0000>;


2) Request 1:1 memory mapping for the dom0less domain

Add a "direct-map" property under the appropriate /chosen/domU node. If
you are using imagebuilder, you can add to boot.source something like
the following line:

    fdt set /chosen/domU0 direct-map <0x1>
