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diff --git a/Documentation/scsi/scsi_fc_transport.txt b/Documentation/scsi/scsi_fc_transport.txt new file mode 100644 index 000000000000..ab057afc757f --- /dev/null +++ b/Documentation/scsi/scsi_fc_transport.txt @@ -0,0 +1,450 @@ + 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 + |