[Nexus 6P General] tenfar:
i don't know,maybe you are right.

this is the property get from my phone.it seems dual sim enabled .not fully working. can't test.it's too complex to understand how the dual sim is working in android. hope someone who have more knowledge with this can help.

enable persist.radio.multisim.config dsds the soft reboot.

root@angler:/ # getprop | grep gsm
[gsm.current.phone-type]: [1,1]
[gsm.defaultpdpcontext.active]: [true]
[gsm.network.type]: [EDGE,Unknown]
[gsm.nitz.time]: [1456890274049]
[gsm.operator.alpha]: [CMCC,CMCC]
[gsm.operator.iso-country]: [cn,cn]
[gsm.operator.isroaming]: [false,false]
[gsm.operator.numeric]: [46000,46000]
[gsm.sim.operator.alpha]: [CMCC,CMCC]
[gsm.sim.operator.iso-country]: [cn,cn]
[gsm.sim.operator.numeric]: [46007,46007]
[gsm.sim.state]: [READY,READY]
[gsm.version.baseband]: [.2.6.1.c4-00008-M8994FAAAANAZM-1]
[gsm.version.baseband1]: [.2.6.1.c4-00008-M8994FAAAANAZM-1]
[gsm.version.ril-impl]: [Qualcomm RIL 1.0]
root@angler:/ # getprop | grep ril
[gsm.version.ril-impl]: [Qualcomm RIL 1.0]
[init.svc.ril-daemon]: [running]
[init.svc.ril-daemon2]: [running]
[init.svc.rild2-wrapper]: [stopped]
[persist.radio.ril_payload_on]: [0]
[ril.ecclist]: [911,112]
[ril.ecclist1]: [911,112]
[ril.qcril_pre_init_lock_held]: [0]
[rild.libpath]: [/system/vendor/lib64/libril-qc-qmi-1.so]
[ro.ril.force_eri_from_xml]: [true]
[ro.ril.svdo]: [false]
[ro.ril.svlte1x]: [false]
root@angler:/ # getprop | grep radio
[persist.radio.adb_log_on]: [0]
[persist.radio.always_send_plmn]: [true]
[persist.radio.apm_sim_not_pwdn]: [1]
[persist.radio.custom_ecc]: [1]
[persist.radio.data_con_rprt]: [true]
[persist.radio.data_no_toggle]: [1]
[persist.radio.default.sub]: [0]
[persist.radio.eons.enabled]: [false]
[persist.radio.mode_pref_nv10]: [1]
[persist.radio.msim.stackid_0]: [0]
[persist.radio.msim.stackid_1]: [1]
[persist.radio.multisim.config]: [dsds]
[persist.radio.redir_party_num]: [0]
[persist.radio.ril_payload_on]: [0]
[persist.radio.sglte_target]: [0]
[persist.radio.snapshot_enabled]: [1]
[persist.radio.snapshot_timer]: [2]
[persist.radio.stack_id_0]: [0]
[persist.radio.stack_id_1]: [1]
[radio.atfwd.start]: [false]
[ro.boot.radio]: [angler-02.50]

after cold reboot :

root@angler:/ # getprop | grep radio
[persist.radio.adb_log_on]: [0]
[persist.radio.always_send_plmn]: [true]
[persist.radio.apm_sim_not_pwdn]: [1]
[persist.radio.custom_ecc]: [1]
[persist.radio.data_con_rprt]: [true]
[persist.radio.data_no_toggle]: [1]
[persist.radio.default.sub]: [0]
[persist.radio.eons.enabled]: [false]
[persist.radio.mode_pref_nv10]: [1]
[persist.radio.msim.stackid_0]: [0]
[persist.radio.msim.stackid_1]: [1]
[persist.radio.multisim.config]: [dsds]
[persist.radio.redir_party_num]: [0]
[persist.radio.ril_payload_on]: [0]
[persist.radio.sglte_target]: [0]
[persist.radio.snapshot_enabled]: [1]
[persist.radio.snapshot_timer]: [2]
[persist.radio.stack_id_0]: [0]
[persist.radio.stack_id_1]: [1]
[ro.boot.radio]: [angler-02.50]
root@angler:/ # getprop | grep gsm
[gsm.current.phone-type]: [1,2]
[gsm.network.type]: [EDGE,Unknown]
[gsm.operator.alpha]: [CHINA MOBILE,正在搜索服务]
[gsm.operator.iso-country]: [cn]
[gsm.operator.isroaming]: [false,false]
[gsm.operator.numeric]: [46000,00000]
[gsm.sim.operator.alpha]: [CMCC]
[gsm.sim.operator.iso-country]: [cn]
[gsm.sim.operator.numeric]: [46007]
[gsm.sim.state]: [READY,ABSENT]
[gsm.version.baseband]: [.2.6.1.c4-00008-M8994FAAAANAZM-1]
[gsm.version.baseband1]: [.2.6.1.c4-00008-M8994FAAAANAZM-1]
[gsm.version.ril-impl]: [Qualcomm RIL 1.0]
root@angler:/ # getprop | grep ril
[gsm.version.ril-impl]: [Qualcomm RIL 1.0]
[init.svc.ril-daemon]: [running]
[init.svc.ril-daemon2]: [running]
[init.svc.rild2-wrapper]: [stopped]
[persist.radio.ril_payload_on]: [0]
[ril.ecclist]: [911,112]
[ril.ecclist1]: [911,112]
[ril.qcril_pre_init_lock_held]: [0]
[rild.libpath]: [/system/vendor/lib64/libril-qc-qmi-1.so]
[ro.ril.force_eri_from_xml]: [true]
[ro.ril.svdo]: [false]
[ro.ril.svlte1x]: [false]