hesela.devNVMe namespace write protection
NVMe namespace write protection is an optional controller capability that restricts changes to a namespace according to its protection state.
Identify Controller reports optional support through NWPC. Basic support covers unprotected and protected states; until-power-cycle and permanent protection have separate capability bits. [2] Get Features identifier 84h reports the configured state. [1]
Ordinary protection survives power cycles and Controller Level Resets but remains changeable. Until-power-cycle protection survives a Controller Level Reset and clears on power cycle. Permanent protection survives both events. Set Features cannot change an already active until-power-cycle or permanent state. Although the feature is not saveable, these persistence rules still apply. [1]
All attached controllers enforce protection. Entering it commits the namespace's volatile cached data and metadata. Configuring protection must not itself set SMART's All Media Read-Only warning. [1]
Relations
- related
- NVMe namespace, NVMe reservation, NVMe Critical Warning, NVMe Format NVM, NVMe sanitize, Read-only mount
Limitations
- Entering until-power-cycle or permanent protection also requires the corresponding RPMB Write Protection Control permission; NWPC support alone is insufficient. Until-power-cycle mode is prohibited in multi-domain subsystems. These entry controls clear on a power cycle or Controller Level Reset; clearing an entry permission does not remove an already active protection state. [1]
Citations
- NVM Express Base 2.3: sections 5.2.26.1.35, 8.1.17 and Figure 690. Copyright 2025 NVM Express, Inc.; all rights reserved.
- libnvme v1.15: nvme_id_ctrl_nwpc capability flags
Further reading
Sources & caveats
- Protocol and pinned API source review; no device command, hardware experiment or immutable-backup certification.