Documentation/scsi/scsi_fc_transport.txt

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