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1.. SPDX-License-Identifier: GPL-2.02 3==============4Devlink Health5==============6 7Background8==========9 10The ``devlink`` health mechanism is targeted for Real Time Alerting, in11order 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 needed16 debugging information.17 18Overview19========20 21The main idea is to unify and centralize driver health reports in the22generic ``devlink`` instance and allow the user to set different23attributes of the health reporting and recovery procedures.24 25The ``devlink`` health reporter:26Device driver creates a "health reporter" per each error/health type.27Error/Health type can be a known/generic (e.g. PCI error, fw error, rx/tx error)28or unknown (driver specific).29For each registered health reporter a driver can issue error/health reports30asynchronously. All health reports handling is done by ``devlink``.31Device driver can provide specific callbacks for each "health reporter", e.g.:32 33 * Recovery procedures34 * Diagnostics procedures35 * Object dump procedures36 * Out Of Box initial parameters37 38Different parts of the driver can register different types of health reporters39with different handlers.40 41Actions42=======43 44Once an error is reported, devlink health will perform the following actions:45 46 * A log is being send to the kernel trace events buffer47 * Health status and statistics are being updated for the reporter instance48 * Object dump is being taken and saved at the reporter instance (as long as49 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 configuration53 - Grace period vs. time passed since last recover54 55Devlink formatted message56=========================57 58To handle devlink health diagnose and health dump requests, devlink creates a59formatted message structure ``devlink_fmsg`` and send it to the driver's callback60to fill the data in using the devlink fmsg API.61 62Devlink fmsg is a mechanism to pass descriptors between drivers and devlink, in63json-like format. The API allows the driver to add nested attributes such as64object, object pair and value array, in addition to attributes such as name and65value.66 67Driver should use this API to fill the fmsg context in a format which will be68translated by the devlink to the netlink message later. When it needs to send69the data using SKBs to the netlink layer, it fragments the data between70different SKBs. In order to do this fragmentation, it uses virtual nests71attributes, to avoid actual nesting use which cannot be divided between72different SKBs.73 74User Interface75==============76 77User can access/change each reporter's parameters and driver specific callbacks78via ``devlink``, e.g per error type (per health reporter):79 80 * Configure reporter's generic parameters (like: disable/enable auto recovery)81 * Invoke recovery procedure82 * Run diagnostics83 * Object dump84 85.. list-table:: List of devlink health interfaces86 :widths: 10 9087 88 * - Name89 - Description90 * - ``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 test98 event in terms of recovery flow should follow closely that of a real99 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 health104 saves a single dump. If an dump is not already stored by devlink105 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 110The following diagram provides a general overview of ``devlink-health``::111 112 netlink113 +--------------------------+114 | |115 | + |116 | | |117 +--------------------------+118 |request for ops119 |(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 +--------+ +--------------------------+139