[SCSI] FC Transport support for vports based on NPIV

                             SCSI FC Tansport

                 =============================================

Date:  4/12/2007

Kernel Revisions for features:

  rports : <<TBS>>

  vports : 2.6.22 (? TBD)

Introduction

============

This file documents the features and components of the SCSI FC Transport.

It also provides documents the API between the transport and FC LLDDs.

The FC transport can be found at:

  drivers/scsi/scsi_transport_fc.c

  include/scsi/scsi_transport_fc.h

  include/scsi/scsi_netlink_fc.h

This file is found at Documentation/scsi/scsi_fc_transport.txt

FC Remote Ports (rports)

========================================================================

<< To Be Supplied >>

FC Virtual Ports (vports)

========================================================================

Overview:

-------------------------------

  New FC standards have defined mechanisms which allows for a single physical

  port to appear on as multiple communication ports. Using the N_Port Id

  Virtualization (NPIV) mechanism, a point-to-point connection to a Fabric

  can be assigned more than 1 N_Port_ID.  Each N_Port_ID appears as a

  separate port to other endpoints on the fabric, even though it shares one

  physical link to the switch for communication. Each N_Port_ID can have a

  unique view of the fabric based on fabric zoning and array lun-masking

  (just like a normal non-NPIV adapter).  Using the Virtual Fabric (VF)

  mechanism, adding a fabric header to each frame allows the port to

  interact with the Fabric Port to join multiple fabrics. The port will

  obtain an N_Port_ID on each fabric it joins. Each fabric will have its

  own unique view of endpoints and configuration parameters.  NPIV may be

  used together with VF so that the port can obtain multiple N_Port_IDs

  on each virtual fabric.

  The FC transport is now recognizing a new object - a vport.  A vport is

  an entity that has a world-wide unique World Wide Port Name (wwpn) and

  World Wide Node Name (wwnn). The transport also allows for the FC4's to

  be specified for the vport, with FCP_Initiator being the primary role

  expected. Once instantiated by one of the above methods, it will have a

  distinct N_Port_ID and view of fabric endpoints and storage entities.

  The fc_host associated with the physical adapter will export the ability

  to create vports. The transport will create the vport object within the

  Linux device tree, and instruct the fc_host's driver to instantiate the

  virtual port. Typically, the driver will create a new scsi_host instance

  on the vport, resulting in a unique <H,C,T,L> namespace for the vport.

  Thus, whether a FC port is based on a physical port or on a virtual port,

  each will appear as a unique scsi_host with its own target and lun space.

  Note: At this time, the transport is written to create only NPIV-based

    vports. However, consideration was given to VF-based vports and it

    should be a minor change to add support if needed.  The remaining

    discussion will concentrate on NPIV.

  Note: World Wide Name assignment (and uniqueness guarantees) are left

    up to an administrative entity controling the vport. For example,

    if vports are to be associated with virtual machines, a XEN mgmt

    utility would be responsible for creating wwpn/wwnn's for the vport,

    using it's own naming authority and OUI. (Note: it already does this

    for virtual MAC addresses).

Device Trees and Vport Objects:

-------------------------------

  Today, the device tree typically contains the scsi_host object,

  with rports and scsi target objects underneath it. Currently the FC

  transport creates the vport object and places it under the scsi_host

  object corresponding to the physical adapter.  The LLDD will allocate

  a new scsi_host for the vport and link it's object under the vport.

  The remainder of the tree under the vports scsi_host is the same

  as the non-NPIV case. The transport is written currently to easily

  allow the parent of the vport to be something other than the scsi_host.

  This could be used in the future to link the object onto a vm-specific

  device tree. If the vport's parent is not the physical port's scsi_host,

  a symbolic link to the vport object will be placed in the physical

  port's scsi_host.

  Here's what to expect in the device tree :

   The typical Physical Port's Scsi_Host:

     /sys/devices/.../host17/

   and it has the typical decendent tree:

     /sys/devices/.../host17/rport-17:0-0/target17:0:0/17:0:0:0:

   and then the vport is created on the Physical Port:

     /sys/devices/.../host17/vport-17:0-0

   and the vport's Scsi_Host is then created:

     /sys/devices/.../host17/vport-17:0-0/host18

   and then the rest of the tree progresses, such as:

     /sys/devices/.../host17/vport-17:0-0/host18/rport-18:0-0/target18:0:0/18:0:0:0:

  Here's what to expect in the sysfs tree :

   scsi_hosts:

     /sys/class/scsi_host/host17                physical port's scsi_host

     /sys/class/scsi_host/host18                vport's scsi_host

   fc_hosts:

     /sys/class/fc_host/host17                  physical port's fc_host

     /sys/class/fc_host/host18                  vport's fc_host

   fc_vports:

     /sys/class/fc_vports/vport-17:0-0          the vport's fc_vport

   fc_rports:

     /sys/class/fc_remote_ports/rport-17:0-0    rport on the physical port

     /sys/class/fc_remote_ports/rport-18:0-0    rport on the vport

Vport Attributes:

-------------------------------

  The new fc_vport class object has the following attributes

     node_name:							Read_Only

       The WWNN of the vport

     port_name:							Read_Only

       The WWPN of the vport

     roles:							Read_Only

       Indicates the FC4 roles enabled on the vport.

     symbolic_name:						Read_Write

       A string, appended to the driver's symbolic port name string, which

       is registered with the switch to identify the vport. For example,

       a hypervisor could set this string to "Xen Domain 2 VM 5 Vport 2",

       and this set of identifiers can be seen on switch management screens

       to identify the port.

     vport_delete:						Write_Only

       When written with a "1", will tear down the vport.

     vport_disable:						Write_Only

       When written with a "1", will transition the vport to a disabled.

       state.  The vport will still be instantiated with the Linux kernel,

       but it will not be active on the FC link.

       When written with a "0", will enable the vport.

     vport_last_state:						Read_Only

       Indicates the previous state of the vport.  See the section below on

       "Vport States".

     vport_state:						Read_Only

       Indicates the state of the vport.  See the section below on

       "Vport States".

     vport_type:						Read_Only

       Reflects the FC mechanism used to create the virtual port.

       Only NPIV is supported currently.

  For the fc_host class object, the following attributes are added for vports:

     max_npiv_vports:						Read_Only

       Indicates the maximum number of NPIV-based vports that the

       driver/adapter can support on the fc_host.

     npiv_vports_inuse:						Read_Only

       Indicates how many NPIV-based vports have been instantiated on the

       fc_host.

     vport_create:						Write_Only

       A "simple" create interface to instantiate a vport on an fc_host.

       A "<WWPN>:<WWNN>" string is written to the attribute. The transport

       then instantiates the vport object and calls the LLDD to create the

       vport with the role of FCP_Initiator.  Each WWN is specified as 16

       hex characters and may *not* contain any prefixes (e.g. 0x, x, etc).

     vport_delete:						Write_Only

        A "simple" delete interface to teardown a vport. A "<WWPN>:<WWNN>"

	string is written to the attribute. The transport will locate the

	vport on the fc_host with the same WWNs and tear it down.  Each WWN

	is specified as 16 hex characters and may *not* contain any prefixes

	(e.g. 0x, x, etc).

Vport States:

-------------------------------

  Vport instantiation consists of two parts:

    - Creation with the kernel and LLDD. This means all transport and

      driver data structures are built up, and device objects created.

      This is equivalent to a driver "attach" on an adapter, which is

      independent of the adapter's link state.

    - Instantiation of the vport on the FC link via ELS traffic, etc.

      This is equivalent to a "link up" and successfull link initialization.

  Futher information can be found in the interfaces section below for

  Vport Creation.

  Once a vport has been instantiated with the kernel/LLDD, a vport state

  can be reported via the sysfs attribute. The following states exist:

    FC_VPORT_UNKNOWN		- Unknown

      An temporary state, typically set only while the vport is being

      instantiated with the kernel and LLDD.

    FC_VPORT_ACTIVE		- Active

      The vport has been successfully been created on the FC link.

      It is fully functional.

    FC_VPORT_DISABLED		- Disabled

      The vport instantiated, but "disabled". The vport is not instantiated

      on the FC link. This is equivalent to a physical port with the

      link "down".

    FC_VPORT_LINKDOWN		- Linkdown

      The vport is not operational as the physical link is not operational.

    FC_VPORT_INITIALIZING	- Initializing

      The vport is in the process of instantiating on the FC link.

      The LLDD will set this state just prior to starting the ELS traffic

      to create the vport. This state will persist until the vport is

      successfully created (state becomes FC_VPORT_ACTIVE) or it fails

      (state is one of the values below).  As this state is transitory,

      it will not be preserved in the "vport_last_state".

    FC_VPORT_NO_FABRIC_SUPP	- No Fabric Support

      The vport is not operational. One of the following conditions were

      encountered:

       - The FC topology is not Point-to-Point

       - The FC port is not connected to an F_Port

       - The F_Port has indicated that NPIV is not supported.

    FC_VPORT_NO_FABRIC_RSCS	- No Fabric Resources

      The vport is not operational. The Fabric failed FDISC with a status

      indicating that it does not have sufficient resources to complete

      the operation.

    FC_VPORT_FABRIC_LOGOUT	- Fabric Logout

      The vport is not operational. The Fabric has LOGO'd the N_Port_ID

      associated with the vport.

    FC_VPORT_FABRIC_REJ_WWN	- Fabric Rejected WWN

      The vport is not operational. The Fabric failed FDISC with a status

      indicating that the WWN's are not valid.

    FC_VPORT_FAILED		- VPort Failed

      The vport is not operational. This is a catchall for all other

      error conditions.

  The following state table indicates the different state transitions:

    State              Event				New State

    --------------------------------------------------------------------

     n/a  		Initialization			Unknown

    Unknown:		Link Down			Linkdown

			Link Up & Loop			No Fabric Support

			Link Up & no Fabric		No Fabric Support

			Link Up & FLOGI response	No Fabric Support

			  indicates no NPIV support

			Link Up & FDISC being sent	Initializing

			Disable request			Disable

    Linkdown:		Link Up				Unknown

    Initializing:	FDISC ACC			Active

			FDISC LS_RJT w/ no resources	No Fabric Resources

			FDISC LS_RJT w/ invalid		Fabric Rejected WWN

			  pname or invalid nport_id

			FDISC LS_RJT failed for		Vport Failed

			  other reasons

			Link Down			Linkdown

			Disable request			Disable

    Disable:		Enable request			Unknown

    Active:		LOGO received from fabric	Fabric Logout

			Link Down			Linkdown

			Disable request			Disable

    Fabric Logout:	Link still up			Unknown

         The following 4 error states all have the same transitions:

    No Fabric Support:

    No Fabric Resources:

    Fabric Rejected WWN:

    Vport Failed:

			Disable request			Disable

			Link goes down			Linkdown

Transport <-> LLDD Interfaces :

-------------------------------

Vport support by LLDD:

  The LLDD indicates support for vports by supplying a vport_create()

  function in the transport template.  The presense of this function will

  cause the creation of the new attributes on the fc_host.  As part of

  the physical port completing its initialization relative to the

  transport, it should set the max_npiv_vports attribute to indicate the

  maximum number of vports the driver and/or adapter supports.

Vport Creation:

  The LLDD vport_create() syntax is:

      int vport_create(struct fc_vport *vport, bool disable)

    where:

      vport:	Is the newly allocated vport object

      disable:	If "true", the vport is to be created in a disabled stated.

		If "false", the vport is to be enabled upon creation.

  When a request is made to create a new vport (via sgio/netlink, or the

  vport_create fc_host attribute), the transport will validate that the LLDD

  can support another vport (e.g. max_npiv_vports > npiv_vports_inuse).

  If not, the create request will be failed.  If space remains, the transport

  will increment the vport count, create the vport object, and then call the

  LLDD's vport_create() function with the newly allocated vport object.

  As mentioned above, vport creation is divided into two parts:

    - Creation with the kernel and LLDD. This means all transport and

      driver data structures are built up, and device objects created.

      This is equivalent to a driver "attach" on an adapter, which is

      independent of the adapter's link state.

    - Instantiation of the vport on the FC link via ELS traffic, etc.

      This is equivalent to a "link up" and successfull link initialization.

  The LLDD's vport_create() function will not synchronously wait for both

  parts to be fully completed before returning. It must validate that the

  infrastructure exists to support NPIV, and complete the first part of

  vport creation (data structure build up) before returning.  We do not

  hinge vport_create() on the link-side operation mainly because:

    - The link may be down. It is not a failure if it is. It simply

      means the vport is in an inoperable state until the link comes up.

      This is consistent with the link bouncing post vport creation.

    - The vport may be created in a disabled state.

    - This is consistent with a model where:  the vport equates to a

      FC adapter. The vport_create is synonymous with driver attachment

      to the adapter, which is independent of link state.

    Note: special error codes have been defined to delineate infrastructure

      failure cases for quicker resolution.

  The expected behavior for the LLDD's vport_create() function is:

    - Validate Infrastructure:

        - If the driver or adapter cannot support another vport, whether

            due to improper firmware, (a lie about) max_npiv, or a lack of

	    some other resource - return VPCERR_UNSUPPORTED.

        - If the driver validates the WWN's against those already active on

            the adapter and detects an overlap - return VPCERR_BAD_WWN.

        - If the driver detects the topology is loop, non-fabric, or the

            FLOGI did not support NPIV - return VPCERR_NO_FABRIC_SUPP.

    - Allocate data structures. If errors are encountered, such as out

        of memory conditions, return the respective negative Exxx error code.

    - If the role is FCP Initiator, the LLDD is to :

        - Call scsi_host_alloc() to allocate a scsi_host for the vport.

	- Call scsi_add_host(new_shost, &vport->dev) to start the scsi_host

	  and bind it as a child of the vport device.

	- Initializes the fc_host attribute values.

    - Kick of further vport state transitions based on the disable flag and

        link state - and return success (zero).

  LLDD Implementers Notes:

  - It is suggested that there be a different fc_function_templates for

    the physical port and the virtual port.  The physical port's template

    would have the vport_create, vport_delete, and vport_disable functions,

    while the vports would not.

  - It is suggested that there be different scsi_host_templates

    for the physical port and virtual port. Likely, there are driver

    attributes, embedded into the scsi_host_template, that are applicable

    for the physical port only (link speed, topology setting, etc). This

    ensures that the attributes are applicable to the respective scsi_host.

Vport Disable/Enable:

  The LLDD vport_disable() syntax is:

      int vport_disable(struct fc_vport *vport, bool disable)

    where:

      vport:	Is vport to to be enabled or disabled

      disable:	If "true", the vport is to be disabled.

		If "false", the vport is to be enabled.

  When a request is made to change the disabled state on a vport, the

  transport will validate the request against the existing vport state.

  If the request is to disable and the vport is already disabled, the

  request will fail. Similarly, if the request is to enable, and the

  vport is not in a disabled state, the request will fail.  If the request

  is valid for the vport state, the transport will call the LLDD to

  change the vport's state.

  Within the LLDD, if a vport is disabled, it remains instantiated with

  the kernel and LLDD, but it is not active or visible on the FC link in

  any way. (see Vport Creation and the 2 part instantiation discussion).

  The vport will remain in this state until it is deleted or re-enabled.

  When enabling a vport, the LLDD reinstantiates the vport on the FC

  link - essentially restarting the LLDD statemachine (see Vport States

  above).

Vport Deletion:

  The LLDD vport_delete() syntax is:

      int vport_delete(struct fc_vport *vport)

    where:

      vport:	Is vport to delete

  When a request is made to delete a vport (via sgio/netlink, or via the

  fc_host or fc_vport vport_delete attributes), the transport will call

  the LLDD to terminate the vport on the FC link, and teardown all other

  datastructures and references.  If the LLDD completes successfully,

  the transport will teardown the vport objects and complete the vport

  removal.  If the LLDD delete request fails, the vport object will remain,

  but will be in an indeterminate state.

  Within the LLDD, the normal code paths for a scsi_host teardown should

  be followed. E.g. If the vport has a FCP Initiator role, the LLDD

  will call fc_remove_host() for the vports scsi_host, followed by

  scsi_remove_host() and scsi_host_put() for the vports scsi_host.

Other:

  fc_host port_type attribute:

    There is a new fc_host port_type value - FC_PORTTYPE_NPIV. This value

    must be set on all vport-based fc_hosts.  Normally, on a physical port,

    the port_type attribute would be set to NPORT, NLPORT, etc based on the

    topology type and existence of the fabric. As this is not applicable to

    a vport, it makes more sense to report the FC mechanism used to create

    the vport.

  Driver unload:

    FC drivers are required to call fc_remove_host() prior to calling

    scsi_remove_host().  This allows the fc_host to tear down all remote

    ports prior the scsi_host being torn down.  The fc_remove_host() call

    was updated to remove all vports for the fc_host as well.

Credits

=======

The following people have contributed to this document:

James Smart

james.smart@emulex.com