Documentation/scsi/scsi_fc_transport.txt

   1                              SCSI FC Tansport
   2                  =============================================
   3
   4 Date:  4/12/2007
   5 Kernel Revisions for features:
   6   rports : <<TBS>>
   7   vports : 2.6.22 (? TBD)
   8
   9
  10 Introduction
  11 ============
  12 This file documents the features and components of the SCSI FC Transport.
  13 It also provides documents the API between the transport and FC LLDDs.
  14 The FC transport can be found at:
  15   drivers/scsi/scsi_transport_fc.c
  16   include/scsi/scsi_transport_fc.h
  17   include/scsi/scsi_netlink_fc.h
  18
  19 This file is found at Documentation/scsi/scsi_fc_transport.txt
  20
  21
  22 FC Remote Ports (rports)
  23 ========================================================================
  24 << To Be Supplied >>
  25
  26
  27 FC Virtual Ports (vports)
  28 ========================================================================
  29
  30 Overview:
  31 -------------------------------
  32
  33   New FC standards have defined mechanisms which allows for a single physical
  34   port to appear on as multiple communication ports. Using the N_Port Id
  35   Virtualization (NPIV) mechanism, a point-to-point connection to a Fabric
  36   can be assigned more than 1 N_Port_ID.  Each N_Port_ID appears as a
  37   separate port to other endpoints on the fabric, even though it shares one
  38   physical link to the switch for communication. Each N_Port_ID can have a
  39   unique view of the fabric based on fabric zoning and array lun-masking
  40   (just like a normal non-NPIV adapter).  Using the Virtual Fabric (VF)
  41   mechanism, adding a fabric header to each frame allows the port to
  42   interact with the Fabric Port to join multiple fabrics. The port will
  43   obtain an N_Port_ID on each fabric it joins. Each fabric will have its
  44   own unique view of endpoints and configuration parameters.  NPIV may be
  45   used together with VF so that the port can obtain multiple N_Port_IDs
  46   on each virtual fabric.
  47
  48   The FC transport is now recognizing a new object - a vport.  A vport is
  49   an entity that has a world-wide unique World Wide Port Name (wwpn) and
  50   World Wide Node Name (wwnn). The transport also allows for the FC4's to
  51   be specified for the vport, with FCP_Initiator being the primary role
  52   expected. Once instantiated by one of the above methods, it will have a
  53   distinct N_Port_ID and view of fabric endpoints and storage entities.
  54   The fc_host associated with the physical adapter will export the ability
  55   to create vports. The transport will create the vport object within the
  56   Linux device tree, and instruct the fc_host's driver to instantiate the
  57   virtual port. Typically, the driver will create a new scsi_host instance
  58   on the vport, resulting in a unique <H,C,T,L> namespace for the vport.
  59   Thus, whether a FC port is based on a physical port or on a virtual port,
  60   each will appear as a unique scsi_host with its own target and lun space.
  61
  62   Note: At this time, the transport is written to create only NPIV-based
  63     vports. However, consideration was given to VF-based vports and it
  64     should be a minor change to add support if needed.  The remaining
  65     discussion will concentrate on NPIV.
  66
  67   Note: World Wide Name assignment (and uniqueness guarantees) are left
  68     up to an administrative entity controlling the vport. For example,
  69     if vports are to be associated with virtual machines, a XEN mgmt
  70     utility would be responsible for creating wwpn/wwnn's for the vport,
  71     using it's own naming authority and OUI. (Note: it already does this
  72     for virtual MAC addresses).
  73
  74
  75 Device Trees and Vport Objects:
  76 -------------------------------
  77
  78   Today, the device tree typically contains the scsi_host object,
  79   with rports and scsi target objects underneath it. Currently the FC
  80   transport creates the vport object and places it under the scsi_host
  81   object corresponding to the physical adapter.  The LLDD will allocate
  82   a new scsi_host for the vport and link it's object under the vport.
  83   The remainder of the tree under the vports scsi_host is the same
  84   as the non-NPIV case. The transport is written currently to easily
  85   allow the parent of the vport to be something other than the scsi_host.
  86   This could be used in the future to link the object onto a vm-specific
  87   device tree. If the vport's parent is not the physical port's scsi_host,
  88   a symbolic link to the vport object will be placed in the physical
  89   port's scsi_host.
  90
  91   Here's what to expect in the device tree :
  92    The typical Physical Port's Scsi_Host:
  93      /sys/devices/.../host17/
  94    and it has the typical descendant tree:
  95      /sys/devices/.../host17/rport-17:0-0/target17:0:0/17:0:0:0:
  96    and then the vport is created on the Physical Port:
  97      /sys/devices/.../host17/vport-17:0-0
  98    and the vport's Scsi_Host is then created:
  99      /sys/devices/.../host17/vport-17:0-0/host18
 100    and then the rest of the tree progresses, such as:
 101      /sys/devices/.../host17/vport-17:0-0/host18/rport-18:0-0/target18:0:0/18:0:0:0:
 102
 103   Here's what to expect in the sysfs tree :
 104    scsi_hosts:
 105      /sys/class/scsi_host/host17                physical port's scsi_host
 106      /sys/class/scsi_host/host18                vport's scsi_host
 107    fc_hosts:
 108      /sys/class/fc_host/host17                  physical port's fc_host
 109      /sys/class/fc_host/host18                  vport's fc_host
 110    fc_vports:
 111      /sys/class/fc_vports/vport-17:0-0          the vport's fc_vport
 112    fc_rports:
 113      /sys/class/fc_remote_ports/rport-17:0-0    rport on the physical port
 114      /sys/class/fc_remote_ports/rport-18:0-0    rport on the vport
 115
 116
 117 Vport Attributes:
 118 -------------------------------
 119
 120   The new fc_vport class object has the following attributes
 121
 122      node_name:                                                 Read_Only
 123        The WWNN of the vport
 124
 125      port_name:                                                 Read_Only
 126        The WWPN of the vport
 127
 128      roles:                                                     Read_Only
 129        Indicates the FC4 roles enabled on the vport.
 130
 131      symbolic_name:                                             Read_Write
 132        A string, appended to the driver's symbolic port name string, which
 133        is registered with the switch to identify the vport. For example,
 134        a hypervisor could set this string to "Xen Domain 2 VM 5 Vport 2",
 135        and this set of identifiers can be seen on switch management screens
 136        to identify the port.
 137
 138      vport_delete:                                              Write_Only
 139        When written with a "1", will tear down the vport.
 140
 141      vport_disable:                                             Write_Only
 142        When written with a "1", will transition the vport to a disabled.
 143        state.  The vport will still be instantiated with the Linux kernel,
 144        but it will not be active on the FC link.
 145        When written with a "0", will enable the vport.
 146
 147      vport_last_state:                                          Read_Only
 148        Indicates the previous state of the vport.  See the section below on
 149        "Vport States".
 150
 151      vport_state:                                               Read_Only
 152        Indicates the state of the vport.  See the section below on
 153        "Vport States".
 154
 155      vport_type:                                                Read_Only
 156        Reflects the FC mechanism used to create the virtual port.
 157        Only NPIV is supported currently.
 158
 159
 160   For the fc_host class object, the following attributes are added for vports:
 161
 162      max_npiv_vports:                                           Read_Only
 163        Indicates the maximum number of NPIV-based vports that the
 164        driver/adapter can support on the fc_host.
 165
 166      npiv_vports_inuse:                                         Read_Only
 167        Indicates how many NPIV-based vports have been instantiated on the
 168        fc_host.
 169
 170      vport_create:                                              Write_Only
 171        A "simple" create interface to instantiate a vport on an fc_host.
 172        A "<WWPN>:<WWNN>" string is written to the attribute. The transport
 173        then instantiates the vport object and calls the LLDD to create the
 174        vport with the role of FCP_Initiator.  Each WWN is specified as 16
 175        hex characters and may *not* contain any prefixes (e.g. 0x, x, etc).
 176
 177      vport_delete:                                              Write_Only
 178         A "simple" delete interface to teardown a vport. A "<WWPN>:<WWNN>"
 179         string is written to the attribute. The transport will locate the
 180         vport on the fc_host with the same WWNs and tear it down.  Each WWN
 181         is specified as 16 hex characters and may *not* contain any prefixes
 182         (e.g. 0x, x, etc).
 183
 184
 185 Vport States:
 186 -------------------------------
 187
 188   Vport instantiation consists of two parts:
 189     - Creation with the kernel and LLDD. This means all transport and
 190       driver data structures are built up, and device objects created.
 191       This is equivalent to a driver "attach" on an adapter, which is
 192       independent of the adapter's link state.
 193     - Instantiation of the vport on the FC link via ELS traffic, etc.
 194       This is equivalent to a "link up" and successful link initialization.
 195   Further information can be found in the interfaces section below for
 196   Vport Creation.
 197
 198   Once a vport has been instantiated with the kernel/LLDD, a vport state
 199   can be reported via the sysfs attribute. The following states exist:
 200
 201     FC_VPORT_UNKNOWN            - Unknown
 202       An temporary state, typically set only while the vport is being
 203       instantiated with the kernel and LLDD.
 204
 205     FC_VPORT_ACTIVE             - Active
 206       The vport has been successfully been created on the FC link.
 207       It is fully functional.
 208
 209     FC_VPORT_DISABLED           - Disabled
 210       The vport instantiated, but "disabled". The vport is not instantiated
 211       on the FC link. This is equivalent to a physical port with the
 212       link "down".
 213
 214     FC_VPORT_LINKDOWN           - Linkdown
 215       The vport is not operational as the physical link is not operational.
 216
 217     FC_VPORT_INITIALIZING       - Initializing
 218       The vport is in the process of instantiating on the FC link.
 219       The LLDD will set this state just prior to starting the ELS traffic
 220       to create the vport. This state will persist until the vport is
 221       successfully created (state becomes FC_VPORT_ACTIVE) or it fails
 222       (state is one of the values below).  As this state is transitory,
 223       it will not be preserved in the "vport_last_state".
 224
 225     FC_VPORT_NO_FABRIC_SUPP     - No Fabric Support
 226       The vport is not operational. One of the following conditions were
 227       encountered:
 228        - The FC topology is not Point-to-Point
 229        - The FC port is not connected to an F_Port
 230        - The F_Port has indicated that NPIV is not supported.
 231
 232     FC_VPORT_NO_FABRIC_RSCS     - No Fabric Resources
 233       The vport is not operational. The Fabric failed FDISC with a status
 234       indicating that it does not have sufficient resources to complete
 235       the operation.
 236
 237     FC_VPORT_FABRIC_LOGOUT      - Fabric Logout
 238       The vport is not operational. The Fabric has LOGO'd the N_Port_ID
 239       associated with the vport.
 240
 241     FC_VPORT_FABRIC_REJ_WWN     - Fabric Rejected WWN
 242       The vport is not operational. The Fabric failed FDISC with a status
 243       indicating that the WWN's are not valid.
 244
 245     FC_VPORT_FAILED             - VPort Failed
 246       The vport is not operational. This is a catchall for all other
 247       error conditions.
 248
 249
 250   The following state table indicates the different state transitions:
 251
 252     State              Event                            New State
 253     --------------------------------------------------------------------
 254      n/a                Initialization                  Unknown
 255     Unknown:            Link Down                       Linkdown
 256                         Link Up & Loop                  No Fabric Support
 257                         Link Up & no Fabric             No Fabric Support
 258                         Link Up & FLOGI response        No Fabric Support
 259                           indicates no NPIV support
 260                         Link Up & FDISC being sent      Initializing
 261                         Disable request                 Disable
 262     Linkdown:           Link Up                         Unknown
 263     Initializing:       FDISC ACC                       Active
 264                         FDISC LS_RJT w/ no resources    No Fabric Resources
 265                         FDISC LS_RJT w/ invalid         Fabric Rejected WWN
 266                           pname or invalid nport_id
 267                         FDISC LS_RJT failed for         Vport Failed
 268                           other reasons
 269                         Link Down                       Linkdown
 270                         Disable request                 Disable
 271     Disable:            Enable request                  Unknown
 272     Active:             LOGO received from fabric       Fabric Logout
 273                         Link Down                       Linkdown
 274                         Disable request                 Disable
 275     Fabric Logout:      Link still up                   Unknown
 276
 277          The following 4 error states all have the same transitions:
 278     No Fabric Support:
 279     No Fabric Resources:
 280     Fabric Rejected WWN:
 281     Vport Failed:
 282                         Disable request                 Disable
 283                         Link goes down                  Linkdown
 284
 285
 286 Transport <-> LLDD Interfaces :
 287 -------------------------------
 288
 289 Vport support by LLDD:
 290
 291   The LLDD indicates support for vports by supplying a vport_create()
 292   function in the transport template.  The presense of this function will
 293   cause the creation of the new attributes on the fc_host.  As part of
 294   the physical port completing its initialization relative to the
 295   transport, it should set the max_npiv_vports attribute to indicate the
 296   maximum number of vports the driver and/or adapter supports.
 297
 298
 299 Vport Creation:
 300
 301   The LLDD vport_create() syntax is:
 302
 303       int vport_create(struct fc_vport *vport, bool disable)
 304
 305     where:
 306       vport:    Is the newly allocated vport object
 307       disable:  If "true", the vport is to be created in a disabled stated.
 308                 If "false", the vport is to be enabled upon creation.
 309
 310   When a request is made to create a new vport (via sgio/netlink, or the
 311   vport_create fc_host attribute), the transport will validate that the LLDD
 312   can support another vport (e.g. max_npiv_vports > npiv_vports_inuse).
 313   If not, the create request will be failed.  If space remains, the transport
 314   will increment the vport count, create the vport object, and then call the
 315   LLDD's vport_create() function with the newly allocated vport object.
 316
 317   As mentioned above, vport creation is divided into two parts:
 318     - Creation with the kernel and LLDD. This means all transport and
 319       driver data structures are built up, and device objects created.
 320       This is equivalent to a driver "attach" on an adapter, which is
 321       independent of the adapter's link state.
 322     - Instantiation of the vport on the FC link via ELS traffic, etc.
 323       This is equivalent to a "link up" and successful link initialization.
 324
 325   The LLDD's vport_create() function will not synchronously wait for both
 326   parts to be fully completed before returning. It must validate that the
 327   infrastructure exists to support NPIV, and complete the first part of
 328   vport creation (data structure build up) before returning.  We do not
 329   hinge vport_create() on the link-side operation mainly because:
 330     - The link may be down. It is not a failure if it is. It simply
 331       means the vport is in an inoperable state until the link comes up.
 332       This is consistent with the link bouncing post vport creation.
 333     - The vport may be created in a disabled state.
 334     - This is consistent with a model where:  the vport equates to a
 335       FC adapter. The vport_create is synonymous with driver attachment
 336       to the adapter, which is independent of link state.
 337
 338     Note: special error codes have been defined to delineate infrastructure
 339       failure cases for quicker resolution.
 340
 341   The expected behavior for the LLDD's vport_create() function is:
 342     - Validate Infrastructure:
 343         - If the driver or adapter cannot support another vport, whether
 344             due to improper firmware, (a lie about) max_npiv, or a lack of
 345             some other resource - return VPCERR_UNSUPPORTED.
 346         - If the driver validates the WWN's against those already active on
 347             the adapter and detects an overlap - return VPCERR_BAD_WWN.
 348         - If the driver detects the topology is loop, non-fabric, or the
 349             FLOGI did not support NPIV - return VPCERR_NO_FABRIC_SUPP.
 350     - Allocate data structures. If errors are encountered, such as out
 351         of memory conditions, return the respective negative Exxx error code.
 352     - If the role is FCP Initiator, the LLDD is to :
 353         - Call scsi_host_alloc() to allocate a scsi_host for the vport.
 354         - Call scsi_add_host(new_shost, &vport->dev) to start the scsi_host
 355           and bind it as a child of the vport device.
 356         - Initializes the fc_host attribute values.
 357     - Kick of further vport state transitions based on the disable flag and
 358         link state - and return success (zero).
 359
 360   LLDD Implementers Notes:
 361   - It is suggested that there be a different fc_function_templates for
 362     the physical port and the virtual port.  The physical port's template
 363     would have the vport_create, vport_delete, and vport_disable functions,
 364     while the vports would not.
 365   - It is suggested that there be different scsi_host_templates
 366     for the physical port and virtual port. Likely, there are driver
 367     attributes, embedded into the scsi_host_template, that are applicable
 368     for the physical port only (link speed, topology setting, etc). This
 369     ensures that the attributes are applicable to the respective scsi_host.
 370
 371
 372 Vport Disable/Enable:
 373
 374   The LLDD vport_disable() syntax is:
 375
 376       int vport_disable(struct fc_vport *vport, bool disable)
 377
 378     where:
 379       vport:    Is vport to to be enabled or disabled
 380       disable:  If "true", the vport is to be disabled.
 381                 If "false", the vport is to be enabled.
 382
 383   When a request is made to change the disabled state on a vport, the
 384   transport will validate the request against the existing vport state.
 385   If the request is to disable and the vport is already disabled, the
 386   request will fail. Similarly, if the request is to enable, and the
 387   vport is not in a disabled state, the request will fail.  If the request
 388   is valid for the vport state, the transport will call the LLDD to
 389   change the vport's state.
 390
 391   Within the LLDD, if a vport is disabled, it remains instantiated with
 392   the kernel and LLDD, but it is not active or visible on the FC link in
 393   any way. (see Vport Creation and the 2 part instantiation discussion).
 394   The vport will remain in this state until it is deleted or re-enabled.
 395   When enabling a vport, the LLDD reinstantiates the vport on the FC
 396   link - essentially restarting the LLDD statemachine (see Vport States
 397   above).
 398
 399
 400 Vport Deletion:
 401
 402   The LLDD vport_delete() syntax is:
 403
 404       int vport_delete(struct fc_vport *vport)
 405
 406     where:
 407       vport:    Is vport to delete
 408
 409   When a request is made to delete a vport (via sgio/netlink, or via the
 410   fc_host or fc_vport vport_delete attributes), the transport will call
 411   the LLDD to terminate the vport on the FC link, and teardown all other
 412   datastructures and references.  If the LLDD completes successfully,
 413   the transport will teardown the vport objects and complete the vport
 414   removal.  If the LLDD delete request fails, the vport object will remain,
 415   but will be in an indeterminate state.
 416
 417   Within the LLDD, the normal code paths for a scsi_host teardown should
 418   be followed. E.g. If the vport has a FCP Initiator role, the LLDD
 419   will call fc_remove_host() for the vports scsi_host, followed by
 420   scsi_remove_host() and scsi_host_put() for the vports scsi_host.
 421
 422
 423 Other:
 424   fc_host port_type attribute:
 425     There is a new fc_host port_type value - FC_PORTTYPE_NPIV. This value
 426     must be set on all vport-based fc_hosts.  Normally, on a physical port,
 427     the port_type attribute would be set to NPORT, NLPORT, etc based on the
 428     topology type and existence of the fabric. As this is not applicable to
 429     a vport, it makes more sense to report the FC mechanism used to create
 430     the vport.
 431
 432   Driver unload:
 433     FC drivers are required to call fc_remove_host() prior to calling
 434     scsi_remove_host().  This allows the fc_host to tear down all remote
 435     ports prior the scsi_host being torn down.  The fc_remove_host() call
 436     was updated to remove all vports for the fc_host as well.
 437
 438
 439 Transport supplied functions
 440 ----------------------------
 441
 442 The following functions are supplied by the FC-transport for use by LLDs.
 443
 444    fc_vport_create - create a vport
 445    fc_vport_terminate - detach and remove a vport
 446
 447 Details:
 448
 449 /**
 450  * fc_vport_create - Admin App or LLDD requests creation of a vport
 451  * @shost:     scsi host the virtual port is connected to.
 452  * @ids:       The world wide names, FC4 port roles, etc for
 453  *              the virtual port.
 454  *
 455  * Notes:
 456  *     This routine assumes no locks are held on entry.
 457  */
 458 struct fc_vport *
 459 fc_vport_create(struct Scsi_Host *shost, struct fc_vport_identifiers *ids)
 460
 461 /**
 462  * fc_vport_terminate - Admin App or LLDD requests termination of a vport
 463  * @vport:      fc_vport to be terminated
 464  *
 465  * Calls the LLDD vport_delete() function, then deallocates and removes
 466  * the vport from the shost and object tree.
 467  *
 468  * Notes:
 469  *      This routine assumes no locks are held on entry.
 470  */
 471 int
 472 fc_vport_terminate(struct fc_vport *vport)
 473
 474
 475 Credits
 476 =======
 477 The following people have contributed to this document:
 478
 479
 480
 481
 482
 483
 484 James Smart
 485 james.smart@emulex.com
 486