gnttab_grant_foreign_access
int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0);
err = gnttab_grant_foreign_access(oeid,
err = gnttab_grant_foreign_access(oeid,
if ((ring_gref = gnttab_grant_foreign_access(oeid,
int gnttab_grant_foreign_access(domid_t, gnttab_frame_t, int readonly);