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[releases.git] / Documentation / networking / devlink / devlink-health.rst
1 .. SPDX-License-Identifier: GPL-2.0
2
3 ==============
4 Devlink Health
5 ==============
6
7 Background
8 ==========
9
10 The ``devlink`` health mechanism is targeted for Real Time Alerting, in
11 order to know when something bad happened to a PCI device.
12
13   * Provide alert debug information.
14   * Self healing.
15   * If problem needs vendor support, provide a way to gather all needed
16     debugging information.
17
18 Overview
19 ========
20
21 The main idea is to unify and centralize driver health reports in the
22 generic ``devlink`` instance and allow the user to set different
23 attributes of the health reporting and recovery procedures.
24
25 The ``devlink`` health reporter:
26 Device driver creates a "health reporter" per each error/health type.
27 Error/Health type can be a known/generic (e.g. PCI error, fw error, rx/tx error)
28 or unknown (driver specific).
29 For each registered health reporter a driver can issue error/health reports
30 asynchronously. All health reports handling is done by ``devlink``.
31 Device driver can provide specific callbacks for each "health reporter", e.g.:
32
33   * Recovery procedures
34   * Diagnostics procedures
35   * Object dump procedures
36   * Out Of Box initial parameters
37
38 Different parts of the driver can register different types of health reporters
39 with different handlers.
40
41 Actions
42 =======
43
44 Once an error is reported, devlink health will perform the following actions:
45
46   * A log is being send to the kernel trace events buffer
47   * Health status and statistics are being updated for the reporter instance
48   * Object dump is being taken and saved at the reporter instance (as long as
49     auto-dump is set and there is no other dump which is already stored)
50   * Auto recovery attempt is being done. Depends on:
51
52     - Auto-recovery configuration
53     - Grace period vs. time passed since last recover
54
55 Devlink formatted message
56 =========================
57
58 To handle devlink health diagnose and health dump requests, devlink creates a
59 formatted message structure ``devlink_fmsg`` and send it to the driver's callback
60 to fill the data in using the devlink fmsg API.
61
62 Devlink fmsg is a mechanism to pass descriptors between drivers and devlink, in
63 json-like format. The API allows the driver to add nested attributes such as
64 object, object pair and value array, in addition to attributes such as name and
65 value.
66
67 Driver should use this API to fill the fmsg context in a format which will be
68 translated by the devlink to the netlink message later. When it needs to send
69 the data using SKBs to the netlink layer, it fragments the data between
70 different SKBs. In order to do this fragmentation, it uses virtual nests
71 attributes, to avoid actual nesting use which cannot be divided between
72 different SKBs.
73
74 User Interface
75 ==============
76
77 User can access/change each reporter's parameters and driver specific callbacks
78 via ``devlink``, e.g per error type (per health reporter):
79
80   * Configure reporter's generic parameters (like: disable/enable auto recovery)
81   * Invoke recovery procedure
82   * Run diagnostics
83   * Object dump
84
85 .. list-table:: List of devlink health interfaces
86    :widths: 10 90
87
88    * - Name
89      - Description
90    * - ``DEVLINK_CMD_HEALTH_REPORTER_GET``
91      - Retrieves status and configuration info per DEV and reporter.
92    * - ``DEVLINK_CMD_HEALTH_REPORTER_SET``
93      - Allows reporter-related configuration setting.
94    * - ``DEVLINK_CMD_HEALTH_REPORTER_RECOVER``
95      - Triggers reporter's recovery procedure.
96    * - ``DEVLINK_CMD_HEALTH_REPORTER_TEST``
97      - Triggers a fake health event on the reporter. The effects of the test
98        event in terms of recovery flow should follow closely that of a real
99        event.
100    * - ``DEVLINK_CMD_HEALTH_REPORTER_DIAGNOSE``
101      - Retrieves current device state related to the reporter.
102    * - ``DEVLINK_CMD_HEALTH_REPORTER_DUMP_GET``
103      - Retrieves the last stored dump. Devlink health
104        saves a single dump. If an dump is not already stored by devlink
105        for this reporter, devlink generates a new dump.
106        Dump output is defined by the reporter.
107    * - ``DEVLINK_CMD_HEALTH_REPORTER_DUMP_CLEAR``
108      - Clears the last saved dump file for the specified reporter.
109
110 The following diagram provides a general overview of ``devlink-health``::
111
112                                                    netlink
113                                           +--------------------------+
114                                           |                          |
115                                           |            +             |
116                                           |            |             |
117                                           +--------------------------+
118                                                        |request for ops
119                                                        |(diagnose,
120       driver                               devlink     |recover,
121                                                        |dump)
122     +--------+                            +--------------------------+
123     |        |                            |    reporter|             |
124     |        |                            |  +---------v----------+  |
125     |        |   ops execution            |  |                    |  |
126     |     <----------------------------------+                    |  |
127     |        |                            |  |                    |  |
128     |        |                            |  + ^------------------+  |
129     |        |                            |    | request for ops     |
130     |        |                            |    | (recover, dump)     |
131     |        |                            |    |                     |
132     |        |                            |  +-+------------------+  |
133     |        |     health report          |  | health handler     |  |
134     |        +------------------------------->                    |  |
135     |        |                            |  +--------------------+  |
136     |        |     health reporter create |                          |
137     |        +---------------------------->                          |
138     +--------+                            +--------------------------+