PV_MODIFIED
pv_table[ppn].pv_pflags &= ~PV_MODIFIED;
rv = (pv_table[ppn].pv_pflags & PV_MODIFIED) != 0;
if ((ppv->pv_pflags & PV_MODIFIED) == 0) {
ppv->pv_pflags |= PV_MODIFIED;
(pflags & PV_REFERENCED) && (pflags & PV_MODIFIED)) {
ppv->pv_pflags |= PV_REFERENCED | PV_MODIFIED;