template< typename _Alloc >
PTE_PTR walk(Va virt, unsigned level, bool force_write_back, _Alloc const &alloc)
{ return _base.walk(_Addr::val(virt), level, force_write_back, alloc); }
template< typename _Alloc >
PTE_PTR walk(Va virt, unsigned level, bool force_write_back, _Alloc const &alloc)
{ return _base.walk(_Addr::val(virt), level, force_write_back, alloc); }