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.. SPDX-License-Identifier: BSD-3-Clause
Copyright(c) 2016 IGEL Co., Ltd.
Poll Mode Driver that wraps vhost library
=========================================
This PMD is a thin wrapper of the DPDK vhost library.
The user can handle virtqueues as one of normal DPDK port.
Vhost Implementation in DPDK
----------------------------
Please refer to Chapter "Vhost Library" of *DPDK Programmer's Guide* to know detail of vhost.
Features and Limitations of vhost PMD
-------------------------------------
Currently, the vhost PMD provides the basic functionality of packet reception, transmission and event handling.
* It has multiple queues support.
* It supports ``RTE_ETH_EVENT_INTR_LSC`` and ``RTE_ETH_EVENT_QUEUE_STATE`` events.
* It supports Port Hotplug functionality.
* Don't need to stop RX/TX, when the user wants to stop a guest or a virtio-net driver on guest.
Runtime Configuration
---------------------
The user can specify below arguments in `--vdev` option.
#. ``iface``:
It is used to specify a path to connect to a QEMU virtio-net device.
#. ``queues``:
It is used to specify the number of queues virtio-net device has.
(Default: 1)
#. ``iommu-support``:
It is used to enable iommu support in vhost library.
(Default: 0 (disabled))
#. ``postcopy-support``:
It is used to enable postcopy live-migration support in vhost library.
(Default: 0 (disabled))
#. ``tso``:
It is used to enable tso support in vhost library.
(Default: 0 (disabled))
#. ``linear-buffer``:
It is used to enable linear buffer support in vhost library.
(Default: 0 (disabled))
#. ``ext-buffer``:
It is used to enable external buffer support in vhost library.
(Default: 0 (disabled))
#. ``legacy-ol-flags``:
It is used to restore legacy behavior for offloading that was not
compliant with offloading API.
(Default: 0 (disabled))
Vhost PMD event handling
------------------------
This section describes how to handle vhost PMD events.
The user can register an event callback handler with ``rte_eth_dev_callback_register()``.
The registered callback handler will be invoked with one of below event types.
#. ``RTE_ETH_EVENT_INTR_LSC``:
It means link status of the port was changed.
#. ``RTE_ETH_EVENT_QUEUE_STATE``:
It means some of queue statuses were changed. Call ``rte_eth_vhost_get_queue_event()`` in the callback handler.
Because changing multiple statuses may occur only one event, call the function repeatedly as long as it doesn't return negative value.
Vhost PMD with testpmd application
----------------------------------
This section demonstrates vhost PMD with testpmd DPDK sample application.
#. Launch the testpmd with vhost PMD:
.. code-block:: console
./dpdk-testpmd -l 0-3 -n 4 --vdev 'net_vhost0,iface=/tmp/sock0,queues=1' -- -i
Other basic DPDK preparations like hugepage enabling here.
Please refer to the *DPDK Getting Started Guide* for detailed instructions.
#. Launch the QEMU:
.. code-block:: console
qemu-system-x86_64 <snip>
-chardev socket,id=chr0,path=/tmp/sock0 \
-netdev vhost-user,id=net0,chardev=chr0,vhostforce,queues=1 \
-device virtio-net-pci,netdev=net0
This command attaches one virtio-net device to QEMU guest.
After initialization processes between QEMU and DPDK vhost library are done, status of the port will be linked up.
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