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Linux 6.18.37 · Networking

Devlink Port

devlink port flavour와 type, multi-controller eswitch, VF·SF function attribute, subfunction lifecycle 및 계층형 TX rate object를 설명합니다.

Source pathDocumentation/networking/devlink/devlink-port.rst
Source versionLinux v6.18.37
TranslationDUJINLABS 전문 번역 + 해설

요약·해설과 원문, 전문 번역을 서로 분리했습니다. API 이름, symbol, source path는 원문 표기를 사용합니다.

1. 요약·해설

원문의 핵심 논리와 kernel programming 관점의 보충 설명입니다. 아래의 전문 번역과는 별도로 작성했습니다.

2. 영어 원문 전체

번역 기준이 된 Linux v6.18.37 원문입니다. 줄 번호는 이 버전의 파일 좌표입니다.

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1 .. SPDX-License-Identifier: GPL-2.0
2
3 .. _devlink_port:
4
5 ============
6 Devlink Port
7 ============
8
9 ``devlink-port`` is a port that exists on the device. It has a logically
10 separate ingress/egress point of the device. A devlink port can be any one
11 of many flavours. A devlink port flavour along with port attributes
12 describe what a port represents.
13
14 A device driver that intends to publish a devlink port sets the
15 devlink port attributes and registers the devlink port.
16
17 Devlink port flavours are described below.
18
19 .. list-table:: List of devlink port flavours
20 :widths: 33 90
21
22 * - Flavour
23 - Description
24 * - ``DEVLINK_PORT_FLAVOUR_PHYSICAL``
25 - Any kind of physical port. This can be an eswitch physical port or any
26 other physical port on the device.
27 * - ``DEVLINK_PORT_FLAVOUR_DSA``
28 - This indicates a DSA interconnect port.
29 * - ``DEVLINK_PORT_FLAVOUR_CPU``
30 - This indicates a CPU port applicable only to DSA.
31 * - ``DEVLINK_PORT_FLAVOUR_PCI_PF``
32 - This indicates an eswitch port representing a port of PCI
33 physical function (PF).
34 * - ``DEVLINK_PORT_FLAVOUR_PCI_VF``
35 - This indicates an eswitch port representing a port of PCI
36 virtual function (VF).
37 * - ``DEVLINK_PORT_FLAVOUR_PCI_SF``
38 - This indicates an eswitch port representing a port of PCI
39 subfunction (SF).
40 * - ``DEVLINK_PORT_FLAVOUR_VIRTUAL``
41 - This indicates a virtual port for the PCI virtual function.
42
43 Devlink port can have a different type based on the link layer described below.
44
45 .. list-table:: List of devlink port types
46 :widths: 23 90
47
48 * - Type
49 - Description
50 * - ``DEVLINK_PORT_TYPE_ETH``
51 - Driver should set this port type when a link layer of the port is
52 Ethernet.
53 * - ``DEVLINK_PORT_TYPE_IB``
54 - Driver should set this port type when a link layer of the port is
55 InfiniBand.
56 * - ``DEVLINK_PORT_TYPE_AUTO``
57 - This type is indicated by the user when driver should detect the port
58 type automatically.
59
60 PCI controllers
61 ---------------
62 In most cases a PCI device has only one controller. A controller consists of
63 potentially multiple physical, virtual functions and subfunctions. A function
64 consists of one or more ports. This port is represented by the devlink eswitch
65 port.
66
67 A PCI device connected to multiple CPUs or multiple PCI root complexes or a
68 SmartNIC, however, may have multiple controllers. For a device with multiple
69 controllers, each controller is distinguished by a unique controller number.
70 An eswitch is on the PCI device which supports ports of multiple controllers.
71
72 An example view of a system with two controllers::
73
74 ---------------------------------------------------------
75 | |
76 | --------- --------- ------- ------- |
77 ----------- | | vf(s) | | sf(s) | |vf(s)| |sf(s)| |
78 | server | | ------- ----/---- ---/----- ------- ---/--- ---/--- |
79 | pci rc |=== | pf0 |______/________/ | pf1 |___/_______/ |
80 | connect | | ------- ------- |
81 ----------- | | controller_num=1 (no eswitch) |
82 ------|--------------------------------------------------
83 (internal wire)
84 |
85 ---------------------------------------------------------
86 | devlink eswitch ports and reps |
87 | ----------------------------------------------------- |
88 | |ctrl-0 | ctrl-0 | ctrl-0 | ctrl-0 | ctrl-0 |ctrl-0 | |
89 | |pf0 | pf0vfN | pf0sfN | pf1 | pf1vfN |pf1sfN | |
90 | ----------------------------------------------------- |
91 | |ctrl-1 | ctrl-1 | ctrl-1 | ctrl-1 | ctrl-1 |ctrl-1 | |
92 | |pf0 | pf0vfN | pf0sfN | pf1 | pf1vfN |pf1sfN | |
93 | ----------------------------------------------------- |
94 | |
95 | |
96 ----------- | --------- --------- ------- ------- |
97 | smartNIC| | | vf(s) | | sf(s) | |vf(s)| |sf(s)| |
98 | pci rc |==| ------- ----/---- ---/----- ------- ---/--- ---/--- |
99 | connect | | | pf0 |______/________/ | pf1 |___/_______/ |
100 ----------- | ------- ------- |
101 | |
102 | local controller_num=0 (eswitch) |
103 ---------------------------------------------------------
104
105 In the above example, the external controller (identified by controller number = 1)
106 doesn't have the eswitch. Local controller (identified by controller number = 0)
107 has the eswitch. The Devlink instance on the local controller has eswitch
108 devlink ports for both the controllers.
109
110 Function configuration
111 ======================
112
113 Users can configure one or more function attributes before enumerating the PCI
114 function. Usually it means, user should configure function attribute
115 before a bus specific device for the function is created. However, when
116 SRIOV is enabled, virtual function devices are created on the PCI bus.
117 Hence, function attribute should be configured before binding virtual
118 function device to the driver. For subfunctions, this means user should
119 configure port function attribute before activating the port function.
120
121 A user may set the hardware address of the function using
122 `devlink port function set hw_addr` command. For Ethernet port function
123 this means a MAC address.
124
125 Users may also set the RoCE capability of the function using
126 `devlink port function set roce` command.
127
128 Users may also set the function as migratable using
129 `devlink port function set migratable` command.
130
131 Users may also set the IPsec crypto capability of the function using
132 `devlink port function set ipsec_crypto` command.
133
134 Users may also set the IPsec packet capability of the function using
135 `devlink port function set ipsec_packet` command.
136
137 Users may also set the maximum IO event queues of the function
138 using `devlink port function set max_io_eqs` command.
139
140 Function attributes
141 ===================
142
143 MAC address setup
144 -----------------
145 The configured MAC address of the PCI VF/SF will be used by netdevice and rdma
146 device created for the PCI VF/SF.
147
148 - Get the MAC address of the VF identified by its unique devlink port index::
149
150 $ devlink port show pci/0000:06:00.0/2
151 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
152 function:
153 hw_addr 00:00:00:00:00:00
154
155 - Set the MAC address of the VF identified by its unique devlink port index::
156
157 $ devlink port function set pci/0000:06:00.0/2 hw_addr 00:11:22:33:44:55
158
159 $ devlink port show pci/0000:06:00.0/2
160 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
161 function:
162 hw_addr 00:11:22:33:44:55
163
164 - Get the MAC address of the SF identified by its unique devlink port index::
165
166 $ devlink port show pci/0000:06:00.0/32768
167 pci/0000:06:00.0/32768: type eth netdev enp6s0pf0sf88 flavour pcisf pfnum 0 sfnum 88
168 function:
169 hw_addr 00:00:00:00:00:00
170
171 - Set the MAC address of the SF identified by its unique devlink port index::
172
173 $ devlink port function set pci/0000:06:00.0/32768 hw_addr 00:00:00:00:88:88
174
175 $ devlink port show pci/0000:06:00.0/32768
176 pci/0000:06:00.0/32768: type eth netdev enp6s0pf0sf88 flavour pcisf pfnum 0 sfnum 88
177 function:
178 hw_addr 00:00:00:00:88:88
179
180 RoCE capability setup
181 ---------------------
182 Not all PCI VFs/SFs require RoCE capability.
183
184 When RoCE capability is disabled, it saves system memory per PCI VF/SF.
185
186 When user disables RoCE capability for a VF/SF, user application cannot send or
187 receive any RoCE packets through this VF/SF and RoCE GID table for this PCI
188 will be empty.
189
190 When RoCE capability is disabled in the device using port function attribute,
191 VF/SF driver cannot override it.
192
193 - Get RoCE capability of the VF device::
194
195 $ devlink port show pci/0000:06:00.0/2
196 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
197 function:
198 hw_addr 00:00:00:00:00:00 roce enable
199
200 - Set RoCE capability of the VF device::
201
202 $ devlink port function set pci/0000:06:00.0/2 roce disable
203
204 $ devlink port show pci/0000:06:00.0/2
205 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
206 function:
207 hw_addr 00:00:00:00:00:00 roce disable
208
209 migratable capability setup
210 ---------------------------
211 Live migration is the process of transferring a live virtual machine
212 from one physical host to another without disrupting its normal
213 operation.
214
215 User who want PCI VFs to be able to perform live migration need to
216 explicitly enable the VF migratable capability.
217
218 When user enables migratable capability for a VF, and the HV binds the VF to VFIO driver
219 with migration support, the user can migrate the VM with this VF from one HV to a
220 different one.
221
222 However, when migratable capability is enable, device will disable features which cannot
223 be migrated. Thus migratable cap can impose limitations on a VF so let the user decide.
224
225 Example of LM with migratable function configuration:
226 - Get migratable capability of the VF device::
227
228 $ devlink port show pci/0000:06:00.0/2
229 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
230 function:
231 hw_addr 00:00:00:00:00:00 migratable disable
232
233 - Set migratable capability of the VF device::
234
235 $ devlink port function set pci/0000:06:00.0/2 migratable enable
236
237 $ devlink port show pci/0000:06:00.0/2
238 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
239 function:
240 hw_addr 00:00:00:00:00:00 migratable enable
241
242 - Bind VF to VFIO driver with migration support::
243
244 $ echo <pci_id> > /sys/bus/pci/devices/0000:08:00.0/driver/unbind
245 $ echo mlx5_vfio_pci > /sys/bus/pci/devices/0000:08:00.0/driver_override
246 $ echo <pci_id> > /sys/bus/pci/devices/0000:08:00.0/driver/bind
247
248 Attach VF to the VM.
249 Start the VM.
250 Perform live migration.
251
252 IPsec crypto capability setup
253 -----------------------------
254 When user enables IPsec crypto capability for a VF, user application can offload
255 XFRM state crypto operation (Encrypt/Decrypt) to this VF.
256
257 When IPsec crypto capability is disabled (default) for a VF, the XFRM state is
258 processed in software by the kernel.
259
260 - Get IPsec crypto capability of the VF device::
261
262 $ devlink port show pci/0000:06:00.0/2
263 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
264 function:
265 hw_addr 00:00:00:00:00:00 ipsec_crypto disabled
266
267 - Set IPsec crypto capability of the VF device::
268
269 $ devlink port function set pci/0000:06:00.0/2 ipsec_crypto enable
270
271 $ devlink port show pci/0000:06:00.0/2
272 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
273 function:
274 hw_addr 00:00:00:00:00:00 ipsec_crypto enabled
275
276 IPsec packet capability setup
277 -----------------------------
278 When user enables IPsec packet capability for a VF, user application can offload
279 XFRM state and policy crypto operation (Encrypt/Decrypt) to this VF, as well as
280 IPsec encapsulation.
281
282 When IPsec packet capability is disabled (default) for a VF, the XFRM state and
283 policy is processed in software by the kernel.
284
285 - Get IPsec packet capability of the VF device::
286
287 $ devlink port show pci/0000:06:00.0/2
288 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
289 function:
290 hw_addr 00:00:00:00:00:00 ipsec_packet disabled
291
292 - Set IPsec packet capability of the VF device::
293
294 $ devlink port function set pci/0000:06:00.0/2 ipsec_packet enable
295
296 $ devlink port show pci/0000:06:00.0/2
297 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
298 function:
299 hw_addr 00:00:00:00:00:00 ipsec_packet enabled
300
301 Maximum IO events queues setup
302 ------------------------------
303 When user sets maximum number of IO event queues for a SF or
304 a VF, such function driver is limited to consume only enforced
305 number of IO event queues.
306
307 IO event queues deliver events related to IO queues, including network
308 device transmit and receive queues (txq and rxq) and RDMA Queue Pairs (QPs).
309 For example, the number of netdevice channels and RDMA device completion
310 vectors are derived from the function's IO event queues. Usually, the number
311 of interrupt vectors consumed by the driver is limited by the number of IO
312 event queues per device, as each of the IO event queues is connected to an
313 interrupt vector.
314
315 - Get maximum IO event queues of the VF device::
316
317 $ devlink port show pci/0000:06:00.0/2
318 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
319 function:
320 hw_addr 00:00:00:00:00:00 ipsec_packet disabled max_io_eqs 10
321
322 - Set maximum IO event queues of the VF device::
323
324 $ devlink port function set pci/0000:06:00.0/2 max_io_eqs 32
325
326 $ devlink port show pci/0000:06:00.0/2
327 pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
328 function:
329 hw_addr 00:00:00:00:00:00 ipsec_packet disabled max_io_eqs 32
330
331 Subfunction
332 ============
333
334 Subfunction is a lightweight function that has a parent PCI function on which
335 it is deployed. Subfunction is created and deployed in unit of 1. Unlike
336 SRIOV VFs, a subfunction doesn't require its own PCI virtual function.
337 A subfunction communicates with the hardware through the parent PCI function.
338
339 To use a subfunction, 3 steps setup sequence is followed:
340
341 1) create - create a subfunction;
342 2) configure - configure subfunction attributes;
343 3) deploy - deploy the subfunction;
344
345 Subfunction management is done using devlink port user interface.
346 User performs setup on the subfunction management device.
347
348 (1) Create
349 ----------
350 A subfunction is created using a devlink port interface. A user adds the
351 subfunction by adding a devlink port of subfunction flavour. The devlink
352 kernel code calls down to subfunction management driver (devlink ops) and asks
353 it to create a subfunction devlink port. Driver then instantiates the
354 subfunction port and any associated objects such as health reporters and
355 representor netdevice.
356
357 (2) Configure
358 -------------
359 A subfunction devlink port is created but it is not active yet. That means the
360 entities are created on devlink side, the e-switch port representor is created,
361 but the subfunction device itself is not created. A user might use e-switch port
362 representor to do settings, putting it into bridge, adding TC rules, etc. A user
363 might as well configure the hardware address (such as MAC address) of the
364 subfunction while subfunction is inactive.
365
366 (3) Deploy
367 ----------
368 Once a subfunction is configured, user must activate it to use it. Upon
369 activation, subfunction management driver asks the subfunction management
370 device to instantiate the subfunction device on particular PCI function.
371 A subfunction device is created on the :ref:`Documentation/driver-api/auxiliary_bus.rst <auxiliary_bus>`.
372 At this point a matching subfunction driver binds to the subfunction's auxiliary device.
373
374 Rate object management
375 ======================
376
377 Devlink provides API to manage tx rates of single devlink port or a group.
378 This is done through rate objects, which can be one of the two types:
379
380 ``leaf``
381 Represents a single devlink port; created/destroyed by the driver. Since leaf
382 have 1to1 mapping to its devlink port, in user space it is referred as
383 ``pci/<bus_addr>/<port_index>``;
384
385 ``node``
386 Represents a group of rate objects (leafs and/or nodes); created/deleted by
387 request from the userspace; initially empty (no rate objects added). In
388 userspace it is referred as ``pci/<bus_addr>/<node_name>``, where
389 ``node_name`` can be any identifier, except decimal number, to avoid
390 collisions with leafs.
391
392 API allows to configure following rate object's parameters:
393
394 ``tx_share``
395 Minimum TX rate value shared among all other rate objects, or rate objects
396 that parts of the parent group, if it is a part of the same group.
397
398 ``tx_max``
399 Maximum TX rate value.
400
401 ``tx_priority``
402 Allows for usage of strict priority arbiter among siblings. This
403 arbitration scheme attempts to schedule nodes based on their priority
404 as long as the nodes remain within their bandwidth limit. The higher the
405 priority the higher the probability that the node will get selected for
406 scheduling.
407
408 ``tx_weight``
409 Allows for usage of Weighted Fair Queuing arbitration scheme among
410 siblings. This arbitration scheme can be used simultaneously with the
411 strict priority. As a node is configured with a higher rate it gets more
412 BW relative to its siblings. Values are relative like a percentage
413 points, they basically tell how much BW should node take relative to
414 its siblings.
415
416 ``parent``
417 Parent node name. Parent node rate limits are considered as additional limits
418 to all node children limits. ``tx_max`` is an upper limit for children.
419 ``tx_share`` is a total bandwidth distributed among children.
420
421 ``tc_bw``
422 Allow users to set the bandwidth allocation per traffic class on rate
423 objects. This enables fine-grained QoS configurations by assigning a relative
424 share value to each traffic class. The bandwidth is distributed in proportion
425 to the share value for each class, relative to the sum of all shares.
426 When applied to a non-leaf node, tc_bw determines how bandwidth is shared
427 among its child elements.
428
429 ``tx_priority`` and ``tx_weight`` can be used simultaneously. In that case
430 nodes with the same priority form a WFQ subgroup in the sibling group
431 and arbitration among them is based on assigned weights.
432
433 Arbitration flow from the high level:
434
435 #. Choose a node, or group of nodes with the highest priority that stays
436 within the BW limit and are not blocked. Use ``tx_priority`` as a
437 parameter for this arbitration.
438
439 #. If group of nodes have the same priority perform WFQ arbitration on
440 that subgroup. Use ``tx_weight`` as a parameter for this arbitration.
441
442 #. Select the winner node, and continue arbitration flow among its children,
443 until leaf node is reached, and the winner is established.
444
445 #. If all the nodes from the highest priority sub-group are satisfied, or
446 overused their assigned BW, move to the lower priority nodes.
447
448 Driver implementations are allowed to support both or either rate object types
449 and setting methods of their parameters. Additionally driver implementation
450 may export nodes/leafs and their child-parent relationships.
451
452 Terms and Definitions
453 =====================
454
455 .. list-table:: Terms and Definitions
456 :widths: 22 90
457
458 * - Term
459 - Definitions
460 * - ``PCI device``
461 - A physical PCI device having one or more PCI buses consists of one or
462 more PCI controllers.
463 * - ``PCI controller``
464 - A controller consists of potentially multiple physical functions,
465 virtual functions and subfunctions.
466 * - ``Port function``
467 - An object to manage the function of a port.
468 * - ``Subfunction``
469 - A lightweight function that has parent PCI function on which it is
470 deployed.
471 * - ``Subfunction device``
472 - A bus device of the subfunction, usually on a auxiliary bus.
473 * - ``Subfunction driver``
474 - A device driver for the subfunction auxiliary device.
475 * - ``Subfunction management device``
476 - A PCI physical function that supports subfunction management.
477 * - ``Subfunction management driver``
478 - A device driver for PCI physical function that supports
479 subfunction management using devlink port interface.
480 * - ``Subfunction host driver``
481 - A device driver for PCI physical function that hosts subfunction
482 devices. In most cases it is same as subfunction management driver. When
483 subfunction is used on external controller, subfunction management and
484 host drivers are different.
485

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