--- /dev/null
+ SCSI FC Tansport
+ =============================================
+
+Date: 11/18/2008
+Kernel Revisions for features:
+ rports : <<TBS>>
+ vports : 2.6.22
+ bsg support : 2.6.30 (?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
+ include/scsi/scsi_bsg_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 controlling 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 its 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 its 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 descendant 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 successful link initialization.
+ Further 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 presence 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 successful 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 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.
+
+
+Transport supplied functions
+----------------------------
+
+The following functions are supplied by the FC-transport for use by LLDs.
+
+ fc_vport_create - create a vport
+ fc_vport_terminate - detach and remove a vport
+
+Details:
+
+/**
+ * fc_vport_create - Admin App or LLDD requests creation of a vport
+ * @shost: scsi host the virtual port is connected to.
+ * @ids: The world wide names, FC4 port roles, etc for
+ * the virtual port.
+ *
+ * Notes:
+ * This routine assumes no locks are held on entry.
+ */
+struct fc_vport *
+fc_vport_create(struct Scsi_Host *shost, struct fc_vport_identifiers *ids)
+
+/**
+ * fc_vport_terminate - Admin App or LLDD requests termination of a vport
+ * @vport: fc_vport to be terminated
+ *
+ * Calls the LLDD vport_delete() function, then deallocates and removes
+ * the vport from the shost and object tree.
+ *
+ * Notes:
+ * This routine assumes no locks are held on entry.
+ */
+int
+fc_vport_terminate(struct fc_vport *vport)
+
+
+FC BSG support (CT & ELS passthru, and more)
+========================================================================
+<< To Be Supplied >>
+
+
+
+
+
+Credits
+=======
+The following people have contributed to this document:
+
+
+
+
+
+
+James Smart
+james.smart@emulex.com
+
Code Review / kvmfornfv.git / blobdiff