| 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 |
| |
