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30 Fail-safe poll mode driver library
31 ==================================
33 The Fail-safe poll mode driver library (**librte_pmd_failsafe**) is a virtual
34 device that allows using any device supporting hotplug (sudden device removal
35 and plugging on its bus), without modifying other components relying on such
36 device (application, other PMDs).
38 Additionally to the Seamless Hotplug feature, the Fail-safe PMD offers the
39 ability to redirect operations to secondary devices when the primary has been
40 removed from the system.
44 The library is enabled by default. You can enable it or disable it manually
45 by setting the ``CONFIG_RTE_LIBRTE_PMD_FAILSAFE`` configuration option.
50 The Fail-safe PMD only supports a limited set of features. If you plan to use a
51 device underneath the Fail-safe PMD with a specific feature, this feature must
52 be supported by the Fail-safe PMD to avoid throwing any error.
54 A notable exception is the device removal feature. The fail-safe PMD being a
55 virtual device, it cannot currently be removed in the sense of a specific bus
56 hotplug, like for PCI for example. It will however enable this feature for its
57 sub-device automatically, detecting those that are capable and register the
58 relevant callback for such event.
60 Check the feature matrix for the complete set of supported features.
65 This option can be modified in the ``$RTE_TARGET/build/.config`` file.
67 - ``CONFIG_RTE_LIBRTE_PMD_FAILSAFE`` (default **y**)
69 Toggle compiling librte_pmd_failsafe.
71 Using the Fail-safe PMD from the EAL command line
72 -------------------------------------------------
74 The Fail-safe PMD can be used like most other DPDK virtual devices, by passing a
75 ``--vdev`` parameter to the EAL when starting the application. The device name
76 must start with the *net_failsafe* prefix, followed by numbers or letters. This
77 name must be unique for each device. Each fail-safe instance must have at least one
78 sub-device, up to ``RTE_MAX_ETHPORTS-1``.
80 A sub-device can be any legal DPDK device, including possibly another fail-safe
83 Fail-safe command line parameters
84 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
86 - **dev(<iface>)** parameter
88 This parameter allows the user to define a sub-device. The ``<iface>`` part of
89 this parameter must be a valid device definition. It could be the argument
90 provided to any ``-w`` device specification or the argument that would be
91 given to a ``--vdev`` parameter (including a fail-safe).
92 Enclosing the device definition within parenthesis here allows using
93 additional sub-device parameters if need be. They will be passed on to the
96 - **exec(<shell command>)** parameter
98 This parameter allows the user to provide a command to the fail-safe PMD to
99 execute and define a sub-device.
100 It is done within a regular shell context.
101 The first line of its output is read by the fail-safe PMD and otherwise
102 interpreted as if passed by the regular **dev** parameter.
103 Any other line is discarded.
104 If the command fail or output an incorrect string, the sub-device is not
106 All commas within the ``shell command`` are replaced by spaces before
107 executing the command. This helps using scripts to specify devices.
109 - **mac** parameter [MAC address]
111 This parameter allows the user to set a default MAC address to the fail-safe
112 and all of its sub-devices.
113 If no default mac address is provided, the fail-safe PMD will read the MAC
114 address of the first of its sub-device to be successfully probed and use it as
115 its default MAC address, trying to set it to all of its other sub-devices.
116 If no sub-device was successfully probed at initialization, then a random MAC
117 address is generated, that will be subsequently applied to all sub-device once
120 - **hotplug_poll** parameter [UINT64] (default **2000**)
122 This parameter allows the user to configure the amount of time in milliseconds
123 between two slave upkeep round.
128 This section shows some example of using **testpmd** with a fail-safe PMD.
130 #. To build a PMD and configure DPDK, refer to the document
131 :ref:`compiling and testing a PMD for a NIC <pmd_build_and_test>`.
133 #. Start testpmd. The slave device should be blacklisted from normal EAL
134 operations to avoid probing it twice when in PCI blacklist mode.
136 .. code-block:: console
138 $RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
139 --vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)'
140 -b 84:00.0 -b 00:04.0 -- -i
142 If the slave device being used is not blacklisted, it will be probed by the
143 EAL first. When the fail-safe then tries to initialize it the probe operation
146 Note that PCI blacklist mode is the default PCI operating mode.
148 #. Alternatively, it can be used alongside any other device in whitelist mode.
150 .. code-block:: console
152 $RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
153 --vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)'
156 #. Start testpmd using a flexible device definition
158 .. code-block:: console
160 $RTE_TARGET/build/app/testpmd -c 0xff -n 4 --no-pci \
161 --vdev='net_failsafe0,exec(echo 84:00.0)' -- -i
163 Using the Fail-safe PMD from an application
164 -------------------------------------------
166 This driver strives to be as seamless as possible to existing applications, in
167 order to propose the hotplug functionality in the easiest way possible.
169 Care must be taken, however, to respect the **ether** API concerning device
170 access, and in particular, using the ``RTE_ETH_FOREACH_DEV`` macro to iterate
171 over ethernet devices, instead of directly accessing them or by writing one's
177 A sub-device can be defined without existing on the system when the fail-safe
178 PMD is initialized. Upon probing this device, the fail-safe PMD will detect its
179 absence and postpone its use. It will then register for a periodic check on any
182 During this time, the fail-safe PMD can be used normally, configured and told to
183 emit and receive packets. It will store any applied configuration, and try to
184 apply it upon the probing of its missing sub-device. After this configuration
185 pass, the new sub-device will be synchronized with other sub-devices, i.e. be
186 started if the fail-safe PMD has been started by the user before.
191 A sub-device supporting the device removal event can be removed from its bus at
192 any time. The fail-safe PMD will register a callback for such event and react
193 accordingly. It will try to safely stop, close and uninit the sub-device having
194 emitted this event, allowing it to free its eventual resources.
199 Fallback device : Secondary device
200 The fail-safe will fail-over onto this device when the preferred device is
203 Preferred device : Primary device
204 The first declared sub-device in the fail-safe parameters.
205 When this device is plugged, it is always used as emitting device.
206 It is the main sub-device and is used as target for configuration
207 operations if there is any ambiguity.
210 Periodical process when slaves are serviced. Each devices having a state
211 different to that of the fail-safe device itself, is synchronized with it.
212 Additionally, each slave having the remove flag set are cleaned-up.
215 In the context of the fail-safe PMD, synonymous to sub-device.
218 A device being utilized by the fail-safe PMD.
219 This is another PMD running underneath the fail-safe PMD.
220 Any sub-device can disappear at any time. The fail-safe will ensure
221 that the device removal happens gracefully.