Documentation/scsi/scsi_fc_transport.rst

   1 .. SPDX-License-Identifier: GPL-2.0
   2
   3 ================
   4 SCSI FC Tansport
   5 ================
   6
   7 Date:  11/18/2008
   8
   9 Kernel Revisions for features::
  10
  11   rports : <<TBS>>
  12   vports : 2.6.22
  13   bsg support : 2.6.30 (?TBD?)
  14
  15
  16 Introduction
  17 ============
  18 This file documents the features and components of the SCSI FC Transport.
  19 It also provides documents the API between the transport and FC LLDDs.
  20
  21 The 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
  28 This file is found at Documentation/scsi/scsi_fc_transport.rst
  29
  30
  31 FC Remote Ports (rports)
  32 ========================
  33 << To Be Supplied >>
  34
  35
  36 FC Virtual Ports (vports)
  37 =========================
  38
  39 Overview
  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
  86 Device 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
 139 Vport 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
 207 Vport 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
 322 The 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
 332 Transport <-> LLDD Interfaces
 333 -----------------------------
 334
 335 Vport 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
 345 Vport 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
 431 Vport 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
 462 Vport 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
 486 Other:
 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
 502 Transport supplied functions
 503 ----------------------------
 504
 505 The 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
 512 Details::
 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
 540 FC BSG support (CT & ELS passthru, and more)
 541 ============================================
 542
 543 << To Be Supplied >>
 544
 545
 546
 547
 548
 549 Credits
 550 =======
 551 The following people have contributed to this document:
 552
 553
 554
 555
 556
 557
 558 James Smart
 559 james.smart@emulex.com
 560