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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 Check the feature matrix for the complete set of supported features.
59 This option can be modified in the ``$RTE_TARGET/build/.config`` file.
61 - ``CONFIG_RTE_LIBRTE_PMD_FAILSAFE`` (default **y**)
63 Toggle compiling librte_pmd_failsafe.
65 Using the Fail-safe PMD from the EAL command line
66 -------------------------------------------------
68 The Fail-safe PMD can be used like most other DPDK virtual devices, by passing a
69 ``--vdev`` parameter to the EAL when starting the application. The device name
70 must start with the *net_failsafe* prefix, followed by numbers or letters. This
71 name must be unique for each device. Each fail-safe instance must have at least one
72 sub-device, up to ``RTE_MAX_ETHPORTS-1``.
74 A sub-device can be any legal DPDK device, including possibly another fail-safe
77 Fail-safe command line parameters
78 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
80 - **dev(<iface>)** parameter
82 This parameter allows the user to define a sub-device. The ``<iface>`` part of
83 this parameter must be a valid device definition. It could be the argument
84 provided to any ``-w`` device specification or the argument that would be
85 given to a ``--vdev`` parameter (including a fail-safe).
86 Enclosing the device definition within parenthesis here allows using
87 additional sub-device parameters if need be. They will be passed on to the
90 - **mac** parameter [MAC address]
92 This parameter allows the user to set a default MAC address to the fail-safe
93 and all of its sub-devices.
94 If no default mac address is provided, the fail-safe PMD will read the MAC
95 address of the first of its sub-device to be successfully probed and use it as
96 its default MAC address, trying to set it to all of its other sub-devices.
97 If no sub-device was successfully probed at initialization, then a random MAC
98 address is generated, that will be subsequently applied to all sub-device once
104 This section shows some example of using **testpmd** with a fail-safe PMD.
106 #. To build a PMD and configure DPDK, refer to the document
107 :ref:`compiling and testing a PMD for a NIC <pmd_build_and_test>`.
109 #. Start testpmd. The slave device should be blacklisted from normal EAL
110 operations to avoid probing it twice when in PCI blacklist mode.
112 .. code-block:: console
114 $RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
115 --vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)'
116 -b 84:00.0 -b 00:04.0 -- -i
118 If the slave device being used is not blacklisted, it will be probed by the
119 EAL first. When the fail-safe then tries to initialize it the probe operation
122 Note that PCI blacklist mode is the default PCI operating mode.
124 #. Alternatively, it can be used alongside any other device in whitelist mode.
126 .. code-block:: console
128 $RTE_TARGET/build/app/testpmd -c 0xff -n 4 \
129 --vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)'
132 Using the Fail-safe PMD from an application
133 -------------------------------------------
135 This driver strives to be as seamless as possible to existing applications, in
136 order to propose the hotplug functionality in the easiest way possible.
138 Care must be taken, however, to respect the **ether** API concerning device
139 access, and in particular, using the ``RTE_ETH_FOREACH_DEV`` macro to iterate
140 over ethernet devices, instead of directly accessing them or by writing one's
146 Fallback device : Secondary device
147 The fail-safe will fail-over onto this device when the preferred device is
150 Preferred device : Primary device
151 The first declared sub-device in the fail-safe parameters.
152 When this device is plugged, it is always used as emitting device.
153 It is the main sub-device and is used as target for configuration
154 operations if there is any ambiguity.
157 In the context of the fail-safe PMD, synonymous to sub-device.
160 A device being utilized by the fail-safe PMD.
161 This is another PMD running underneath the fail-safe PMD.
162 Any sub-device can disappear at any time. The fail-safe will ensure
163 that the device removal happens gracefully.