docs/designs/power-systems-memory-preserving-reboot.md

1 # Memory preserving reboot and System Dump extraction flow on POWER Systems
17 based servers to create a memory dump required for the debugging. This document
18 explains the high-level flow of warm reboot and extraction of the resulting dump
45 - **System Dump**: A dump of main memory and hardware states for debugging the
82 collects the hardware data and memory contents to create a dump file in the host
89 - System dump should be collected irrespective of the availability of an
92 - It should provide a mechanism for the user to request a system dump.
106 - Error log associated with dump needs to be part of the dump package
108 - A dump summary should be created with size and other details of the dump
110 - Once the dump is generated, the hypervisor should notify BMC.
112 - Hypervisor should offload the dump to BMC to transfer to an external client.
114 - Provide Redfish interfaces to manage dump
116 - A tool to collect the dump from the server.
118 - A method to parse the content of the dump.
124 The flow of the memory preserving reboot and system dump offloading
125 ![Memory preserving reboot and dump extraction flow](https://user-images.githubusercontent.com/1666…
139 #### 3 - Initiate System Dump
166 to the right location, move the memory contents to create the dump.
168 #### 8 - Hypervisor Formats dump and sends notification to BMC
170 Once the hypervisor is started, it formats the dump and sends a notification to
171 BMC through PLDM and with the dump size PLDM calls the dump manager interface to
172 notify the dump. Dump manager creates a dBus object for the new dump, with
173 status not offloaded and dump size. BMC web catches the object creation signal
176 #### 9 - HMC send request to dump offload
178 Once HMC is ready to offload, it creates NBD server and send dump offload
179 request to BMC. BMCWeb creates an NBD client and NBD proxy to offload the dump.
180 BMC dump manager make a PLDM call with dump id provided by hypervisor and the
181 NBD device id. PLDM sends the offload request to the hypervisor with the dump
184 #### 10 - Hypervisor starts dump offload
186 Hypervisor start sending down the dump packets through DMA PLDM reads the DUMP
188 and get written to a dump file.
195 #### 12 - HMC verifies dump and send dump DELETE to BMC
197 HMC verifies the dump and send dump delete request to BMC BMC sends the dump
198 delete message to hypervisor Hypervisor deletes dump in host memory.
204 ### Dump offload sequence
206 ![Dump offload sequence](https://user-images.githubusercontent.com/16666879/77681614-9e158780-6fbb-…
210 Offload the dump from hypervisor to external dump collection application instead
218 - PLDM on BMC and Host - Extensions to PLDM implementation to pass type of dump,
219   and notification of new dump file to dump manager.
222 - Dump manager on BMC - BMC dump manager supports dump stored on BMC and that
225 - External dump offloading application needs to support NBD based offload
227 - Proposing a new redfish schema for dump operations.
228   [Redfish Dump Proposal](https://lists.ozlabs.org/pipermail/openbmc/2019-December/019827.html)
230 - BMC Web needs to implement new redfish specification for dump.
240 - Unit test plans - Test dump manager interfaces using busctl - Test reboot by
246   - User-initiated dump testing, which invokes a memory preserving reboot to
247     collect dump.
249   - Offload dump collected in host.
251 - System Dump test plan
252   - Automated tests to initiate and offload dump as part of test bucket.