1# Dump Manager Design 2 3Author: 4 Dhruvaraj Subhashchandran <dhruvaraj@in.ibm.com> 5 6Primary assignee: 7 Dhruvaraj Subhashchandran <dhruvaraj@in.ibm.com> 8 9Other contributors: 10 11Created: 12/12/2019 12 13## Problem Description 14During a crash or a host failure, an event monitor mechanism generates an error 15log, but the size of the error log is limited to few kilobytes, so all the data 16from the crash or failure may not fit into an error log. The additional data 17required for the debugging needs to be collected as a dump. 18The existing OpenBMC dump interfaces support only the dumps generated on 19the BMC and dump manager doesn't support download operations. 20 21## Glossary 22 23- **System Dump**: A dump of the Host's main memory and processor registers. 24 [Read More](https://en.wikipedia.org/wiki/Core_dump) 25- **Memory Preserving Reboot(MPR)**: A method of reboot with preserving the 26 contents of the volatile memory 27- **PLDM**: An interface and data model to access low-level platform inventory, 28 monitoring, control, event, and data/parameters transfer functions. 29 [ReadMore](https://github.com/openbmc/docs/blob/master/designs/pldm-stack.md) 30- **Machine Check Exception**: A severe error inside a processor core that 31 causes a processor core to stop all processing activities. 32- **BMCWeb**: An embedded webserver for OpenBMC. [More Info](https://github.com/openbmc/bmcweb/blob/master/README.md) 33 34## Background and References 35Various types of dumps are created based on the type and source of failure. 36The dump manager, which is orchestrating the collection and offload, needs to 37provide methods to create, store the dump details, and offload it. Additionally, 38some sources allow the dump to be extracted manually without a failure to 39understand the current state or analyze a suspected problems. 40 41### Type of dumps supported. 42These are some of the dumps supported by dump manager. 43 44#### BMC Dump 45A dump collected when there is a failure in the BMC with various debug 46information. This type of dump can be generated by user too to get the current 47state of the BMC. This dump gets collected on BMC and stored on BMC 48 49#### System Dump 50A system dump is a collection of debugging information from the host, this may 51include host memory and/or register data. This dump can be initiated by BMC and 52there can be system reboots while collecting the dump. Dump gets stored in the 53host memory and offloaded through the BMC or get collected directly to BMC based 54on the size of dump contents and the available space on the BMC to store the 55dump. 56 57#### Resource dump 58A special type of host dump is initiated and collected by the host based on the 59request from a user. No system state change may be necessary during the 60collection of this kind of a dump. A resource indicator may be used to indicate 61what data to be collected. The content of the dump can be decided by the host. 62This dump can be stored in host memory and offloaded through BMC or host can 63send this dump down to BMC once the collection is completed based on the size 64of the dump and the availability of space on the BMC. 65 66#### Hostboot dump 67A dump that can be collected during the boot failure of the host. This dump may 68or may not include the contents of the main memory and/or the processor registers. 69 70#### Hardware dump 71This dump can be collected during a critical failure on the hardware 72components like the processor while the host is booted and running. The host may 73stop during this dump and may collect various processor states and/or memory 74contents to help to debug the failure. 75 76## Requirements 77 78 79#### Dump manager needs to provide interfaces for 80- Create a dump: Initiate the creation of the dump, based on an error condition 81 or a user request. 82- List the dumps: List all dumps present in the BMC. 83- Get a dump: Offload the dump to an external entity. 84- Notify: Notify the dump manager that a new dump is created. 85- Delete the dump. 86- Mark a dump as offloaded to an external entity. 87- Set the dump policies like disabling a type of dump or dump overwriting policy. 88 89## Proposed Design 90There are various types of dumps; interfaces are standard for most of the dumps, 91but huge dumps which cannot be stored on the BMC needs additional support. 92This document will explain the design of different types of dumps. The dumps are 93classified based on where it is collected, stored, and how it is extracted. Two 94major types are 95 96- Collected by BMC and stored on BMC. 97- Collected and stored on an attached entity but offloaded through BMC. 98 99This proposal focuses on re-using the existing [phosphor-debug-collector](https://github.com/openbmc/phosphor-debug-collector), which 100collects the dumps from BMC. 101 102 103 104 105#### Brief design points of existing phosphor-debug-collector 106- A create interface which assumes the type is BMC dump and returns an ID to the 107 caller for the user-initiated dumps. 108- An external request of dump is considered as a user-initiated BMC dump and 109 initiate BMC dump collection with a tool named dreport with type manual dump 110- The dreport create dump file in the dump path provided by the dump manager code. 111- A watch process is forked by the dump manager to catch the signal for the file 112 close on that path and assume the dump collection is completed. 113- The watch process calls an internal dbus interface to create the dump entry 114 with size and timestamp. 115- The path of dump is based on the predefined base path and the id of the dump. 116- When the request comes for offload, the file is downloaded from the dump base 117 path +id, no update in the entry whether dump is offloaded 118- Deleting a dump by deleting the entry and internal file also will be deleted. 119- There are system generated dumps based on error log or core dump, which works 120 similar to user-initiated dumps with the following difference. 121- No external create D-Bus interface is needed, but a monitor application will 122 monitor for specific conditions like the existence of a core file or a signal 123 for new error log creation of a few selected types. 124- Once the event occurred, the monitor will call an internal D-Bus interface 125 dump manager to create the dump with the type of dump. 126- The dump manager calls dreport with a dump type got from the monitor and write 127 data to a path based on dump id. 128 129#### Updates proposed to the existing phosphor-debug-collector. 130- External D-Bus interface needs to specify the type of the dump since a user 131 can request multiple types of dumps 132- Create will be returning an id which can be mapped to the actual dump once it 133 is created. 134- A Notify interface is provided for notifying the creation of a dump outside 135 the BMC but offloaded through BMC. 136- The InitiateOffload function will be implemented to download the dump. 137- Status of the dump, whether offloaded or not, will be added to the dump entry. 138 139### Dump manager interfaces. 140- Dump Manager DBus object provides interfaces for creating and managing dump 141 142- Interfaces 143 - **Create**: The interface to create a dump, called by clients to initiate 144 user-initiated dump. 145 - Type: Type of the dump needs to be created 146 147 - **Notify**: Notify the dump manager that a new dump is created. 148 - ID: ID of the dump, if not 0 this will be the external id of the dump 149 - Type: Type of dump that was created. 150 - Size: Size of the dump 151 152 ### Dump entry interfaces 153 - **InitiateOffload**: Initiate the offload of the dump. 154 - OffloadUri: The URI where the dump should be offloaded. 155 156#### The properties common to all dumps 157There will be a base dump entry with properties common to all types of dumps 158- ID: Id of the dump 159- Timestamp: Dump creation timestamp 160- Size: Total size of the dump 161- OffloadComplete: Set to true when offload is completed 162- OffloadURI: The URI for offloading the dump, set while initiating the offload. 163Specific types need to inherit from this common dump entry class 164and add specific properties. 165 166#### Additional propertries based on dump types 167 168##### BMC Dump 169- No Additional properties 170 171##### System Dump 172- External Source ID: ID provided by the Host, this id will be used for all 173 communication to the source of the dump, in this case, Host. 174 175 176### Flow of dumps collected and stored in the Host 177PLDM is provided as an example dump transport and notification mechanism 178between Host and BMC. 179 180- Create: Initiate methods to create the dump in Host. 181- Generating the dump in Host 182- Host notifies the creation of dump through PLDM to BMC. 183- PLDM call Notify to create the dump entry 184- InitiateOffload: Dump manager request Host to start offload 185- The Host sends the dump through PLDM, and PLDM on BMC sends it out. 186 187 188## Alternatives Considered 189- Offloading Host dumps through Host instead of BMC, but considered BMC option 190 due to following reasons 191 - The BMC is considered the "management path" of most servers and often 192 the Host is not connected to the desired network for the offload 193 location. 194 - BMC provides one common point for all dumps generated in the system 195 for external management appliance. 196 197## Impacts 198- The existing BMC dump interface needs to be re-used. The current interface is 199 not accepting a dump type, so a new interface to create the dump with type 200 will be provided for BMC dump also without changing the existing interface. 201- Modifying the BMC dump infrastructure to support additional dumps. 202- openpower-proc-control will be updated to call memory preserving chip-ops and 203 to handle memory preserving reboot on POWER platforms. 204- Additional system state to indicate the system is collecting debug data 205 While performing memory preserving reboot. 206 207 208## Testing 209- Unit tests to make sure the dump manager interfaces are working. 210- Following integration tests will be executed to make sure the dump manager 211is working as expected. 212 - Test creating host dumps and offloading it. 213 - Test deleting host dumps 214 - Create/List/Offload/Delete BMC dumps to make sure existing 215 dump manager functions are not broken. 216- Automated tests for dump Create/List/Offload/Delete to avoid regression. 217
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