gnttab_grant_foreign_access_ref
gnttab_grant_foreign_access_ref(gr, gs->gs_oeid, mfn, !gs->gs_isread);
gnttab_grant_foreign_access_ref(txp->tx_txreq.gref,
gnttab_grant_foreign_access_ref(bufp->grant_ref,
gnttab_grant_foreign_access_ref(ringp->xr_gref, xvdi_get_oeid(dip),
void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,