dh_dvma
dh->dh_dvma, dh->dh_maplen,
dva = (u_long)(dh->dh_dvma);
dh->dh_dvma = 0;
data_pa = dh->dh_dvma;
dh->dh_dvma, dh->dh_maplen,
dva = (u_long)(dh->dh_dvma);