_PTE_EMPTY
dat_ptep_xchg(ptep, _PTE_EMPTY, gfn, asce, has_skeys);
if (READ_ONCE(*ptep).val != _PTE_EMPTY.val)
dat_ptep_xchg(ptep, _PTE_EMPTY, r_gfn, sg->asce, uses_skeys(sg));
pgste = gmap_ptep_xchg(priv->gmap, ptep, _PTE_EMPTY, pgste, gfn);
if (oldpte.val == _PTE_EMPTY.val || oldpte.h.pfra == f->pfn) {