| .. _mpipl: |
| |
| MPIPL (aka FADUMP) Overview |
| =========================== |
| |
| Memory Preserving Initial Program Load (MPIPL) is a Power feature where the |
| contents of memory are preserved while the system reboots after a failure. |
| This is accomplished by the firmware/OS publishing ranges of memory to be |
| preserved across boots. |
| |
| Registration |
| ------------ |
| In the OPAL context, OPAL and host Linux communicate the memory ranges to be |
| preserved via source descriptor tables in the HDAT (MDST and MDDT table inside |
| SPIRAH). Host Linux can register/unregister using OPAL_MPIPL_UPDATE API (see |
| :ref:`opal-api-mpipl`). |
| |
| Initiating dump |
| --------------- |
| Whenever Linux crashes, it makes reboot2 OPAL call with type as MPIPL. (see |
| :ref:`opal-api-cec-reboot`). Depending on sevice processor type OPAL makes |
| appropriate call to initiate MPIPL. On FSP system we call `attn` instruction |
| (see ``__trigger_attn()``) and on BMC system we call SBE `S0 interrupt` |
| (see ``p9_sbe_terminate()``). |
| |
| Dump collection |
| --------------- |
| Hostboot then re-IPLs the machine taking care to copy over contents of the |
| source memory to a alternate memory locations as specified in descriptor table. |
| Hostboot publishes this information in the result descriptor tables (MDRT table |
| inside SPIRAH structure). The success/failure of the copy is indicated by a |
| results table. |
| |
| SBE/Hostboot also does the requisite procedures to gather hardware register |
| states for all active threads at the time of the crash. |
| |
| MPIPL boot |
| ---------- |
| On MPIPL boot, OPAL adds device tree entry (``/ibm,opal/dump/mpipl-boot``) |
| to indicate its MPIPL boot. Kernel will use OPAL_MPIPL_QUERY_TAG API |
| (:ref:`opal-api-mpipl`) to retrieve metadata tag. Kernel then uses its |
| existing logic (kdump/fadump) to write out a core dump of OPAL and Linux |
| kernel in a format that GDB and crash can understand. |
| |
| Device tree |
| ----------- |
| We create new device tree node (``/ibm,opal/dump``) to pass dump details to Linux |
| kernel from OPAL (see :ref:`device-tree/ibm,opal/dump`). |
