235 lines
10 KiB
ReStructuredText
235 lines
10 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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.. _devlink_port:
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============
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Devlink Port
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============
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``devlink-port`` is a port that exists on the device. It has a logically
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separate ingress/egress point of the device. A devlink port can be any one
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of many flavours. A devlink port flavour along with port attributes
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describe what a port represents.
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A device driver that intends to publish a devlink port sets the
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devlink port attributes and registers the devlink port.
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Devlink port flavours are described below.
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.. list-table:: List of devlink port flavours
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:widths: 33 90
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* - Flavour
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- Description
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* - ``DEVLINK_PORT_FLAVOUR_PHYSICAL``
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- Any kind of physical port. This can be an eswitch physical port or any
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other physical port on the device.
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* - ``DEVLINK_PORT_FLAVOUR_DSA``
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- This indicates a DSA interconnect port.
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* - ``DEVLINK_PORT_FLAVOUR_CPU``
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- This indicates a CPU port applicable only to DSA.
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* - ``DEVLINK_PORT_FLAVOUR_PCI_PF``
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- This indicates an eswitch port representing a port of PCI
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physical function (PF).
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* - ``DEVLINK_PORT_FLAVOUR_PCI_VF``
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- This indicates an eswitch port representing a port of PCI
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virtual function (VF).
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* - ``DEVLINK_PORT_FLAVOUR_PCI_SF``
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- This indicates an eswitch port representing a port of PCI
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subfunction (SF).
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* - ``DEVLINK_PORT_FLAVOUR_VIRTUAL``
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- This indicates a virtual port for the PCI virtual function.
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Devlink port can have a different type based on the link layer described below.
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.. list-table:: List of devlink port types
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:widths: 23 90
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* - Type
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- Description
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* - ``DEVLINK_PORT_TYPE_ETH``
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- Driver should set this port type when a link layer of the port is
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Ethernet.
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* - ``DEVLINK_PORT_TYPE_IB``
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- Driver should set this port type when a link layer of the port is
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InfiniBand.
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* - ``DEVLINK_PORT_TYPE_AUTO``
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- This type is indicated by the user when driver should detect the port
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type automatically.
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PCI controllers
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---------------
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In most cases a PCI device has only one controller. A controller consists of
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potentially multiple physical, virtual functions and subfunctions. A function
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consists of one or more ports. This port is represented by the devlink eswitch
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port.
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A PCI device connected to multiple CPUs or multiple PCI root complexes or a
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SmartNIC, however, may have multiple controllers. For a device with multiple
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controllers, each controller is distinguished by a unique controller number.
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An eswitch is on the PCI device which supports ports of multiple controllers.
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An example view of a system with two controllers::
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---------------------------------------------------------
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| --------- --------- ------- ------- |
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----------- | | vf(s) | | sf(s) | |vf(s)| |sf(s)| |
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| server | | ------- ----/---- ---/----- ------- ---/--- ---/--- |
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| pci rc |=== | pf0 |______/________/ | pf1 |___/_______/ |
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| connect | | ------- ------- |
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----------- | | controller_num=1 (no eswitch) |
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------|--------------------------------------------------
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(internal wire)
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---------------------------------------------------------
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| devlink eswitch ports and reps |
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| ----------------------------------------------------- |
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| |ctrl-0 | ctrl-0 | ctrl-0 | ctrl-0 | ctrl-0 |ctrl-0 | |
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| |pf0 | pf0vfN | pf0sfN | pf1 | pf1vfN |pf1sfN | |
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| ----------------------------------------------------- |
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| |ctrl-1 | ctrl-1 | ctrl-1 | ctrl-1 | ctrl-1 |ctrl-1 | |
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| |pf0 | pf0vfN | pf0sfN | pf1 | pf1vfN |pf1sfN | |
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| ----------------------------------------------------- |
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----------- | --------- --------- ------- ------- |
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| smartNIC| | | vf(s) | | sf(s) | |vf(s)| |sf(s)| |
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| pci rc |==| ------- ----/---- ---/----- ------- ---/--- ---/--- |
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| connect | | | pf0 |______/________/ | pf1 |___/_______/ |
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----------- | ------- ------- |
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| local controller_num=0 (eswitch) |
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---------------------------------------------------------
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In the above example, the external controller (identified by controller number = 1)
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doesn't have the eswitch. Local controller (identified by controller number = 0)
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has the eswitch. The Devlink instance on the local controller has eswitch
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devlink ports for both the controllers.
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Function configuration
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======================
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A user can configure the function attribute before enumerating the PCI
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function. Usually it means, user should configure function attribute
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before a bus specific device for the function is created. However, when
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SRIOV is enabled, virtual function devices are created on the PCI bus.
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Hence, function attribute should be configured before binding virtual
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function device to the driver. For subfunctions, this means user should
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configure port function attribute before activating the port function.
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A user may set the hardware address of the function using
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'devlink port function set hw_addr' command. For Ethernet port function
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this means a MAC address.
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Subfunction
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============
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Subfunction is a lightweight function that has a parent PCI function on which
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it is deployed. Subfunction is created and deployed in unit of 1. Unlike
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SRIOV VFs, a subfunction doesn't require its own PCI virtual function.
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A subfunction communicates with the hardware through the parent PCI function.
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To use a subfunction, 3 steps setup sequence is followed.
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(1) create - create a subfunction;
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(2) configure - configure subfunction attributes;
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(3) deploy - deploy the subfunction;
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Subfunction management is done using devlink port user interface.
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User performs setup on the subfunction management device.
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(1) Create
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----------
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A subfunction is created using a devlink port interface. A user adds the
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subfunction by adding a devlink port of subfunction flavour. The devlink
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kernel code calls down to subfunction management driver (devlink ops) and asks
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it to create a subfunction devlink port. Driver then instantiates the
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subfunction port and any associated objects such as health reporters and
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representor netdevice.
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(2) Configure
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-------------
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A subfunction devlink port is created but it is not active yet. That means the
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entities are created on devlink side, the e-switch port representor is created,
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but the subfunction device itself is not created. A user might use e-switch port
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representor to do settings, putting it into bridge, adding TC rules, etc. A user
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might as well configure the hardware address (such as MAC address) of the
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subfunction while subfunction is inactive.
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(3) Deploy
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----------
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Once a subfunction is configured, user must activate it to use it. Upon
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activation, subfunction management driver asks the subfunction management
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device to instantiate the subfunction device on particular PCI function.
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A subfunction device is created on the :ref:`Documentation/driver-api/auxiliary_bus.rst <auxiliary_bus>`.
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At this point a matching subfunction driver binds to the subfunction's auxiliary device.
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Rate object management
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======================
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Devlink provides API to manage tx rates of single devlink port or a group.
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This is done through rate objects, which can be one of the two types:
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``leaf``
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Represents a single devlink port; created/destroyed by the driver. Since leaf
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have 1to1 mapping to its devlink port, in user space it is referred as
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``pci/<bus_addr>/<port_index>``;
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``node``
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Represents a group of rate objects (leafs and/or nodes); created/deleted by
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request from the userspace; initially empty (no rate objects added). In
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userspace it is referred as ``pci/<bus_addr>/<node_name>``, where
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``node_name`` can be any identifier, except decimal number, to avoid
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collisions with leafs.
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API allows to configure following rate object's parameters:
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``tx_share``
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Minimum TX rate value shared among all other rate objects, or rate objects
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that parts of the parent group, if it is a part of the same group.
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``tx_max``
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Maximum TX rate value.
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``parent``
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Parent node name. Parent node rate limits are considered as additional limits
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to all node children limits. ``tx_max`` is an upper limit for children.
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``tx_share`` is a total bandwidth distributed among children.
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Driver implementations are allowed to support both or either rate object types
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and setting methods of their parameters.
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Terms and Definitions
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=====================
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.. list-table:: Terms and Definitions
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:widths: 22 90
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* - Term
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- Definitions
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* - ``PCI device``
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- A physical PCI device having one or more PCI buses consists of one or
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more PCI controllers.
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* - ``PCI controller``
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- A controller consists of potentially multiple physical functions,
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virtual functions and subfunctions.
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* - ``Port function``
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- An object to manage the function of a port.
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* - ``Subfunction``
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- A lightweight function that has parent PCI function on which it is
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deployed.
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* - ``Subfunction device``
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- A bus device of the subfunction, usually on a auxiliary bus.
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* - ``Subfunction driver``
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- A device driver for the subfunction auxiliary device.
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* - ``Subfunction management device``
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- A PCI physical function that supports subfunction management.
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* - ``Subfunction management driver``
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- A device driver for PCI physical function that supports
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subfunction management using devlink port interface.
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* - ``Subfunction host driver``
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- A device driver for PCI physical function that hosts subfunction
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devices. In most cases it is same as subfunction management driver. When
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subfunction is used on external controller, subfunction management and
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host drivers are different.
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