1.. SPDX-License-Identifier: GPL-2.0
2
3=================
4SCSI FC Transport
5=================
6
7Date:  11/18/2008
8
9Kernel Revisions for features::
10
11  rports : <<TBS>>
12  vports : 2.6.22
13  bsg support : 2.6.30 (?TBD?)
14
15
16Introduction
17============
18This file documents the features and components of the SCSI FC Transport.
19It also provides documents the API between the transport and FC LLDDs.
20
21The FC transport can be found at::
22
23  drivers/scsi/scsi_transport_fc.c
24  include/scsi/scsi_transport_fc.h
25  include/scsi/scsi_netlink_fc.h
26  include/scsi/scsi_bsg_fc.h
27
28This file is found at Documentation/scsi/scsi_fc_transport.rst
29
30
31FC Remote Ports (rports)
32========================
33<< To Be Supplied >>
34
35
36FC Virtual Ports (vports)
37=========================
38
39Overview
40--------
41
42  New FC standards have defined mechanisms which allows for a single physical
43  port to appear on as multiple communication ports. Using the N_Port Id
44  Virtualization (NPIV) mechanism, a point-to-point connection to a Fabric
45  can be assigned more than 1 N_Port_ID.  Each N_Port_ID appears as a
46  separate port to other endpoints on the fabric, even though it shares one
47  physical link to the switch for communication. Each N_Port_ID can have a
48  unique view of the fabric based on fabric zoning and array lun-masking
49  (just like a normal non-NPIV adapter).  Using the Virtual Fabric (VF)
50  mechanism, adding a fabric header to each frame allows the port to
51  interact with the Fabric Port to join multiple fabrics. The port will
52  obtain an N_Port_ID on each fabric it joins. Each fabric will have its
53  own unique view of endpoints and configuration parameters.  NPIV may be
54  used together with VF so that the port can obtain multiple N_Port_IDs
55  on each virtual fabric.
56
57  The FC transport is now recognizing a new object - a vport.  A vport is
58  an entity that has a world-wide unique World Wide Port Name (wwpn) and
59  World Wide Node Name (wwnn). The transport also allows for the FC4's to
60  be specified for the vport, with FCP_Initiator being the primary role
61  expected. Once instantiated by one of the above methods, it will have a
62  distinct N_Port_ID and view of fabric endpoints and storage entities.
63  The fc_host associated with the physical adapter will export the ability
64  to create vports. The transport will create the vport object within the
65  Linux device tree, and instruct the fc_host's driver to instantiate the
66  virtual port. Typically, the driver will create a new scsi_host instance
67  on the vport, resulting in a unique <H,C,T,L> namespace for the vport.
68  Thus, whether a FC port is based on a physical port or on a virtual port,
69  each will appear as a unique scsi_host with its own target and lun space.
70
71  .. Note::
72    At this time, the transport is written to create only NPIV-based
73    vports. However, consideration was given to VF-based vports and it
74    should be a minor change to add support if needed.  The remaining
75    discussion will concentrate on NPIV.
76
77  .. Note::
78    World Wide Name assignment (and uniqueness guarantees) are left
79    up to an administrative entity controlling the vport. For example,
80    if vports are to be associated with virtual machines, a XEN mgmt
81    utility would be responsible for creating wwpn/wwnn's for the vport,
82    using its own naming authority and OUI. (Note: it already does this
83    for virtual MAC addresses).
84
85
86Device Trees and Vport Objects:
87-------------------------------
88
89  Today, the device tree typically contains the scsi_host object,
90  with rports and scsi target objects underneath it. Currently the FC
91  transport creates the vport object and places it under the scsi_host
92  object corresponding to the physical adapter.  The LLDD will allocate
93  a new scsi_host for the vport and link its object under the vport.
94  The remainder of the tree under the vports scsi_host is the same
95  as the non-NPIV case. The transport is written currently to easily
96  allow the parent of the vport to be something other than the scsi_host.
97  This could be used in the future to link the object onto a vm-specific
98  device tree. If the vport's parent is not the physical port's scsi_host,
99  a symbolic link to the vport object will be placed in the physical
100  port's scsi_host.
101
102  Here's what to expect in the device tree :
103
104   The typical Physical Port's Scsi_Host::
105
106     /sys/devices/.../host17/
107
108   and it has the typical descendant tree::
109
110     /sys/devices/.../host17/rport-17:0-0/target17:0:0/17:0:0:0:
111
112   and then the vport is created on the Physical Port::
113
114     /sys/devices/.../host17/vport-17:0-0
115
116   and the vport's Scsi_Host is then created::
117
118     /sys/devices/.../host17/vport-17:0-0/host18
119
120   and then the rest of the tree progresses, such as::
121
122     /sys/devices/.../host17/vport-17:0-0/host18/rport-18:0-0/target18:0:0/18:0:0:0:
123
124  Here's what to expect in the sysfs tree::
125
126   scsi_hosts:
127     /sys/class/scsi_host/host17                physical port's scsi_host
128     /sys/class/scsi_host/host18                vport's scsi_host
129   fc_hosts:
130     /sys/class/fc_host/host17                  physical port's fc_host
131     /sys/class/fc_host/host18                  vport's fc_host
132   fc_vports:
133     /sys/class/fc_vports/vport-17:0-0          the vport's fc_vport
134   fc_rports:
135     /sys/class/fc_remote_ports/rport-17:0-0    rport on the physical port
136     /sys/class/fc_remote_ports/rport-18:0-0    rport on the vport
137
138
139Vport Attributes
140----------------
141
142  The new fc_vport class object has the following attributes
143
144     node_name:                                                 Read_Only
145       The WWNN of the vport
146
147     port_name:                                                 Read_Only
148       The WWPN of the vport
149
150     roles:                                                     Read_Only
151       Indicates the FC4 roles enabled on the vport.
152
153     symbolic_name:                                             Read_Write
154       A string, appended to the driver's symbolic port name string, which
155       is registered with the switch to identify the vport. For example,
156       a hypervisor could set this string to "Xen Domain 2 VM 5 Vport 2",
157       and this set of identifiers can be seen on switch management screens
158       to identify the port.
159
160     vport_delete:                                              Write_Only
161       When written with a "1", will tear down the vport.
162
163     vport_disable:                                             Write_Only
164       When written with a "1", will transition the vport to a disabled.
165       state.  The vport will still be instantiated with the Linux kernel,
166       but it will not be active on the FC link.
167       When written with a "0", will enable the vport.
168
169     vport_last_state:                                          Read_Only
170       Indicates the previous state of the vport.  See the section below on
171       "Vport States".
172
173     vport_state:                                               Read_Only
174       Indicates the state of the vport.  See the section below on
175       "Vport States".
176
177     vport_type:                                                Read_Only
178       Reflects the FC mechanism used to create the virtual port.
179       Only NPIV is supported currently.
180
181
182  For the fc_host class object, the following attributes are added for vports:
183
184     max_npiv_vports:                                           Read_Only
185       Indicates the maximum number of NPIV-based vports that the
186       driver/adapter can support on the fc_host.
187
188     npiv_vports_inuse:                                         Read_Only
189       Indicates how many NPIV-based vports have been instantiated on the
190       fc_host.
191
192     vport_create:                                              Write_Only
193       A "simple" create interface to instantiate a vport on an fc_host.
194       A "<WWPN>:<WWNN>" string is written to the attribute. The transport
195       then instantiates the vport object and calls the LLDD to create the
196       vport with the role of FCP_Initiator.  Each WWN is specified as 16
197       hex characters and may *not* contain any prefixes (e.g. 0x, x, etc).
198
199     vport_delete:                                              Write_Only
200        A "simple" delete interface to teardown a vport. A "<WWPN>:<WWNN>"
201        string is written to the attribute. The transport will locate the
202        vport on the fc_host with the same WWNs and tear it down.  Each WWN
203        is specified as 16 hex characters and may *not* contain any prefixes
204        (e.g. 0x, x, etc).
205
206
207Vport States
208------------
209
210  Vport instantiation consists of two parts:
211
212    - Creation with the kernel and LLDD. This means all transport and
213      driver data structures are built up, and device objects created.
214      This is equivalent to a driver "attach" on an adapter, which is
215      independent of the adapter's link state.
216    - Instantiation of the vport on the FC link via ELS traffic, etc.
217      This is equivalent to a "link up" and successful link initialization.
218
219  Further information can be found in the interfaces section below for
220  Vport Creation.
221
222  Once a vport has been instantiated with the kernel/LLDD, a vport state
223  can be reported via the sysfs attribute. The following states exist:
224
225    FC_VPORT_UNKNOWN            - Unknown
226      An temporary state, typically set only while the vport is being
227      instantiated with the kernel and LLDD.
228
229    FC_VPORT_ACTIVE             - Active
230      The vport has been successfully been created on the FC link.
231      It is fully functional.
232
233    FC_VPORT_DISABLED           - Disabled
234      The vport instantiated, but "disabled". The vport is not instantiated
235      on the FC link. This is equivalent to a physical port with the
236      link "down".
237
238    FC_VPORT_LINKDOWN           - Linkdown
239      The vport is not operational as the physical link is not operational.
240
241    FC_VPORT_INITIALIZING       - Initializing
242      The vport is in the process of instantiating on the FC link.
243      The LLDD will set this state just prior to starting the ELS traffic
244      to create the vport. This state will persist until the vport is
245      successfully created (state becomes FC_VPORT_ACTIVE) or it fails
246      (state is one of the values below).  As this state is transitory,
247      it will not be preserved in the "vport_last_state".
248
249    FC_VPORT_NO_FABRIC_SUPP     - No Fabric Support
250      The vport is not operational. One of the following conditions were
251      encountered:
252
253       - The FC topology is not Point-to-Point
254       - The FC port is not connected to an F_Port
255       - The F_Port has indicated that NPIV is not supported.
256
257    FC_VPORT_NO_FABRIC_RSCS     - No Fabric Resources
258      The vport is not operational. The Fabric failed FDISC with a status
259      indicating that it does not have sufficient resources to complete
260      the operation.
261
262    FC_VPORT_FABRIC_LOGOUT      - Fabric Logout
263      The vport is not operational. The Fabric has LOGO'd the N_Port_ID
264      associated with the vport.
265
266    FC_VPORT_FABRIC_REJ_WWN     - Fabric Rejected WWN
267      The vport is not operational. The Fabric failed FDISC with a status
268      indicating that the WWN's are not valid.
269
270    FC_VPORT_FAILED             - VPort Failed
271      The vport is not operational. This is a catchall for all other
272      error conditions.
273
274
275  The following state table indicates the different state transitions:
276
277   +------------------+--------------------------------+---------------------+
278   | State            | Event                          | New State           |
279   +==================+================================+=====================+
280   | n/a              | Initialization                 | Unknown             |
281   +------------------+--------------------------------+---------------------+
282   | Unknown:         | Link Down                      | Linkdown            |
283   |                  +--------------------------------+---------------------+
284   |                  | Link Up & Loop                 | No Fabric Support   |
285   |                  +--------------------------------+---------------------+
286   |                  | Link Up & no Fabric            | No Fabric Support   |
287   |                  +--------------------------------+---------------------+
288   |                  | Link Up & FLOGI response       | No Fabric Support   |
289   |                  | indicates no NPIV support      |                     |
290   |                  +--------------------------------+---------------------+
291   |                  | Link Up & FDISC being sent     | Initializing        |
292   |                  +--------------------------------+---------------------+
293   |                  | Disable request                | Disable             |
294   +------------------+--------------------------------+---------------------+
295   | Linkdown:        | Link Up                        | Unknown             |
296   +------------------+--------------------------------+---------------------+
297   | Initializing:    | FDISC ACC                      | Active              |
298   |                  +--------------------------------+---------------------+
299   |                  | FDISC LS_RJT w/ no resources   | No Fabric Resources |
300   |                  +--------------------------------+---------------------+
301   |                  | FDISC LS_RJT w/ invalid        | Fabric Rejected WWN |
302   |		      | pname or invalid nport_id      |                     |
303   |                  +--------------------------------+---------------------+
304   |                  | FDISC LS_RJT failed for        | Vport Failed        |
305   |                  | other reasons                  |                     |
306   |                  +--------------------------------+---------------------+
307   |                  | Link Down                      | Linkdown            |
308   |                  +--------------------------------+---------------------+
309   |                  | Disable request                | Disable             |
310   +------------------+--------------------------------+---------------------+
311   | Disable:         | Enable request                 | Unknown             |
312   +------------------+--------------------------------+---------------------+
313   | Active:          | LOGO received from fabric      | Fabric Logout       |
314   |                  +--------------------------------+---------------------+
315   |                  | Link Down                      | Linkdown            |
316   |                  +--------------------------------+---------------------+
317   |                  | Disable request                | Disable             |
318   +------------------+--------------------------------+---------------------+
319   | Fabric Logout:   | Link still up                  | Unknown             |
320   +------------------+--------------------------------+---------------------+
321
322The following 4 error states all have the same transitions::
323
324    No Fabric Support:
325    No Fabric Resources:
326    Fabric Rejected WWN:
327    Vport Failed:
328                        Disable request                 Disable
329                        Link goes down                  Linkdown
330
331
332Transport <-> LLDD Interfaces
333-----------------------------
334
335Vport support by LLDD:
336
337  The LLDD indicates support for vports by supplying a vport_create()
338  function in the transport template.  The presence of this function will
339  cause the creation of the new attributes on the fc_host.  As part of
340  the physical port completing its initialization relative to the
341  transport, it should set the max_npiv_vports attribute to indicate the
342  maximum number of vports the driver and/or adapter supports.
343
344
345Vport Creation:
346
347  The LLDD vport_create() syntax is::
348
349      int vport_create(struct fc_vport *vport, bool disable)
350
351  where:
352
353      =======   ===========================================================
354      vport     Is the newly allocated vport object
355      disable   If "true", the vport is to be created in a disabled stated.
356                If "false", the vport is to be enabled upon creation.
357      =======   ===========================================================
358
359  When a request is made to create a new vport (via sgio/netlink, or the
360  vport_create fc_host attribute), the transport will validate that the LLDD
361  can support another vport (e.g. max_npiv_vports > npiv_vports_inuse).
362  If not, the create request will be failed.  If space remains, the transport
363  will increment the vport count, create the vport object, and then call the
364  LLDD's vport_create() function with the newly allocated vport object.
365
366  As mentioned above, vport creation is divided into two parts:
367
368    - Creation with the kernel and LLDD. This means all transport and
369      driver data structures are built up, and device objects created.
370      This is equivalent to a driver "attach" on an adapter, which is
371      independent of the adapter's link state.
372    - Instantiation of the vport on the FC link via ELS traffic, etc.
373      This is equivalent to a "link up" and successful link initialization.
374
375  The LLDD's vport_create() function will not synchronously wait for both
376  parts to be fully completed before returning. It must validate that the
377  infrastructure exists to support NPIV, and complete the first part of
378  vport creation (data structure build up) before returning.  We do not
379  hinge vport_create() on the link-side operation mainly because:
380
381    - The link may be down. It is not a failure if it is. It simply
382      means the vport is in an inoperable state until the link comes up.
383      This is consistent with the link bouncing post vport creation.
384    - The vport may be created in a disabled state.
385    - This is consistent with a model where:  the vport equates to a
386      FC adapter. The vport_create is synonymous with driver attachment
387      to the adapter, which is independent of link state.
388
389  .. Note::
390
391      special error codes have been defined to delineate infrastructure
392      failure cases for quicker resolution.
393
394  The expected behavior for the LLDD's vport_create() function is:
395
396    - Validate Infrastructure:
397
398        - If the driver or adapter cannot support another vport, whether
399            due to improper firmware, (a lie about) max_npiv, or a lack of
400            some other resource - return VPCERR_UNSUPPORTED.
401        - If the driver validates the WWN's against those already active on
402            the adapter and detects an overlap - return VPCERR_BAD_WWN.
403        - If the driver detects the topology is loop, non-fabric, or the
404            FLOGI did not support NPIV - return VPCERR_NO_FABRIC_SUPP.
405
406    - Allocate data structures. If errors are encountered, such as out
407        of memory conditions, return the respective negative Exxx error code.
408    - If the role is FCP Initiator, the LLDD is to :
409
410        - Call scsi_host_alloc() to allocate a scsi_host for the vport.
411        - Call scsi_add_host(new_shost, &vport->dev) to start the scsi_host
412          and bind it as a child of the vport device.
413        - Initializes the fc_host attribute values.
414
415    - Kick of further vport state transitions based on the disable flag and
416        link state - and return success (zero).
417
418  LLDD Implementers Notes:
419
420  - It is suggested that there be a different fc_function_templates for
421    the physical port and the virtual port.  The physical port's template
422    would have the vport_create, vport_delete, and vport_disable functions,
423    while the vports would not.
424  - It is suggested that there be different scsi_host_templates
425    for the physical port and virtual port. Likely, there are driver
426    attributes, embedded into the scsi_host_template, that are applicable
427    for the physical port only (link speed, topology setting, etc). This
428    ensures that the attributes are applicable to the respective scsi_host.
429
430
431Vport Disable/Enable:
432
433  The LLDD vport_disable() syntax is::
434
435      int vport_disable(struct fc_vport *vport, bool disable)
436
437  where:
438
439      =======   =======================================
440      vport     Is vport to be enabled or disabled
441      disable   If "true", the vport is to be disabled.
442                If "false", the vport is to be enabled.
443      =======   =======================================
444
445  When a request is made to change the disabled state on a vport, the
446  transport will validate the request against the existing vport state.
447  If the request is to disable and the vport is already disabled, the
448  request will fail. Similarly, if the request is to enable, and the
449  vport is not in a disabled state, the request will fail.  If the request
450  is valid for the vport state, the transport will call the LLDD to
451  change the vport's state.
452
453  Within the LLDD, if a vport is disabled, it remains instantiated with
454  the kernel and LLDD, but it is not active or visible on the FC link in
455  any way. (see Vport Creation and the 2 part instantiation discussion).
456  The vport will remain in this state until it is deleted or re-enabled.
457  When enabling a vport, the LLDD reinstantiates the vport on the FC
458  link - essentially restarting the LLDD statemachine (see Vport States
459  above).
460
461
462Vport Deletion:
463
464  The LLDD vport_delete() syntax is::
465
466      int vport_delete(struct fc_vport *vport)
467
468  where:
469
470      vport:    Is vport to delete
471
472  When a request is made to delete a vport (via sgio/netlink, or via the
473  fc_host or fc_vport vport_delete attributes), the transport will call
474  the LLDD to terminate the vport on the FC link, and teardown all other
475  datastructures and references.  If the LLDD completes successfully,
476  the transport will teardown the vport objects and complete the vport
477  removal.  If the LLDD delete request fails, the vport object will remain,
478  but will be in an indeterminate state.
479
480  Within the LLDD, the normal code paths for a scsi_host teardown should
481  be followed. E.g. If the vport has a FCP Initiator role, the LLDD
482  will call fc_remove_host() for the vports scsi_host, followed by
483  scsi_remove_host() and scsi_host_put() for the vports scsi_host.
484
485
486Other:
487  fc_host port_type attribute:
488    There is a new fc_host port_type value - FC_PORTTYPE_NPIV. This value
489    must be set on all vport-based fc_hosts.  Normally, on a physical port,
490    the port_type attribute would be set to NPORT, NLPORT, etc based on the
491    topology type and existence of the fabric. As this is not applicable to
492    a vport, it makes more sense to report the FC mechanism used to create
493    the vport.
494
495  Driver unload:
496    FC drivers are required to call fc_remove_host() prior to calling
497    scsi_remove_host().  This allows the fc_host to tear down all remote
498    ports prior the scsi_host being torn down.  The fc_remove_host() call
499    was updated to remove all vports for the fc_host as well.
500
501
502Transport supplied functions
503----------------------------
504
505The following functions are supplied by the FC-transport for use by LLDs.
506
507   ==================   =========================
508   fc_vport_create      create a vport
509   fc_vport_terminate   detach and remove a vport
510   ==================   =========================
511
512Details::
513
514    /**
515    * fc_vport_create - Admin App or LLDD requests creation of a vport
516    * @shost:     scsi host the virtual port is connected to.
517    * @ids:       The world wide names, FC4 port roles, etc for
518    *              the virtual port.
519    *
520    * Notes:
521    *     This routine assumes no locks are held on entry.
522    */
523    struct fc_vport *
524    fc_vport_create(struct Scsi_Host *shost, struct fc_vport_identifiers *ids)
525
526    /**
527    * fc_vport_terminate - Admin App or LLDD requests termination of a vport
528    * @vport:      fc_vport to be terminated
529    *
530    * Calls the LLDD vport_delete() function, then deallocates and removes
531    * the vport from the shost and object tree.
532    *
533    * Notes:
534    *      This routine assumes no locks are held on entry.
535    */
536    int
537    fc_vport_terminate(struct fc_vport *vport)
538
539
540FC BSG support (CT & ELS passthru, and more)
541============================================
542
543<< To Be Supplied >>
544
545
546
547
548
549Credits
550=======
551The following people have contributed to this document:
552
553
554
555
556
557
558James Smart
559james.smart@broadcom.com
560
561