/*
* GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
* by devices and/or host CPUs. If successful, <handle> is a tracking number
* that must be presented later to destroy the mapping(s). On error, <handle>
* is a negative status code.
* NOTES:
* 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
* via which I/O devices may access the granted frame.
* 2. If GNTMAP_host_map is specified then a mapping will be added at
* either a host virtual address in the current address space, or at
* a PTE at the specified machine address. The type of mapping to
* perform is selected through the GNTMAP_contains_pte flag, and the
* address is specified in <host_addr>.
* 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
* host mapping is destroyed by other means then it is *NOT* guaranteed
* to be accounted to the correct grant reference!
*/