lm_bd_chain_bds_per_page
DbgBreakIf(0 != (lm_bd_chain_bds_per_page(bd_chain) & BIT_VEC64_ELEM_MASK));
DbgBreakIf(BIT_VEC64_ELEM_SZ >= lm_bd_chain_bds_per_page(bd_chain));
bd_entry = (lm_bd_chain_bds_per_page(bd_chain) * i) - lm_bd_chain_bds_skip_eop(bd_chain);