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+..  SPDX-License-Identifier: BSD-3-Clause
+    Copyright(c) Microsoft Corporation.
+
+Netvsc poll mode driver
+=======================
+
+The Netvsc Poll Mode driver (PMD) provides support for the paravirtualized
+network device for Microsoft Hyper-V. It can be used with
+Window Server 2008/2012/2016, Windows 10.
+The device offers multi-queue support (if kernel and host support it),
+checksum and segmentation offloads.
+
+
+Features and Limitations of Hyper-V PMD
+---------------------------------------
+
+In this release, the hyper PMD driver provides the basic functionality of packet reception and transmission.
+
+*   It supports merge-able buffers per packet when receiving packets and scattered buffer per packet
+    when transmitting packets. The packet size supported is from 64 to 65536.
+
+*   The PMD supports multicast packets and promiscuous mode subject to restrictions on the host.
+    In order to this to work, the guest network configuration on Hyper-V must be configured to allow MAC address
+    spoofing.
+
+*   The device has only a single MAC address.
+    Hyper-V driver does not support MAC or VLAN filtering because the Hyper-V host does not support it.
+
+*   VLAN tags are always stripped and presented in mbuf tci field.
+
+*   The Hyper-V driver does not use or support Link State or Rx interrupt.
+
+*   The maximum number of queues is limited by the host (currently 64).
+    When used with 4.16 kernel only a single queue is available.
+
+.. note::
+   This driver is intended for use with **Hyper-V only** and is
+   not recommended for use on Azure because accelerated Networking
+   (SR-IOV) is not supported.
+
+   On Azure, use the :doc:`vdev_netvsc` which
+   automatically configures the necessary TAP and failsave drivers.
+
+
+Installation
+------------
+
+The Netvsc PMD is a standalone driver, similar to virtio and vmxnet3.
+Using Netvsc PMD requires that the associated VMBUS device be bound to the userspace
+I/O device driver for Hyper-V (uio_hv_generic). By default, all netvsc devices
+will be bound to the Linux kernel driver; in order to use netvsc PMD the
+device must first be overridden.
+
+The first step is to identify the network device to override.
+VMBUS uses Universal Unique Identifiers
+(`UUID`_) to identify devices on the bus similar to how PCI uses Domain:Bus:Function.
+The UUID associated with a Linux kernel network device can be determined
+by looking at the sysfs information. To find the UUID for eth1 and
+store it in a shell variable:
+
+    .. code-block:: console
+
+	DEV_UUID=$(basename $(readlink /sys/class/net/eth1/device))
+
+
+.. _`UUID`: https://en.wikipedia.org/wiki/Universally_unique_identifier
+
+There are several possible ways to assign the uio device driver for a device.
+The easiest way (but only on 4.18 or later)
+is to use the `driverctl Device Driver control utility`_ to override
+the normal kernel device.
+
+    .. code-block:: console
+
+	driverctl -b vmbus set-override $DEV_UUID uio_hv_generic
+
+.. _`driverctl Device Driver control utility`: https://gitlab.com/driverctl/driverctl
+
+Any settings done with driverctl are by default persistent and will be reapplied
+on reboot.
+
+On older kernels, the same effect can be had by manual sysfs bind and unbind
+operations:
+
+    .. code-block:: console
+
+	NET_UUID="f8615163-df3e-46c5-913f-f2d2f965ed0e"
+	modprobe uio_hv_generic
+	echo $NET_UUID > /sys/bus/vmbus/drivers/uio_hv_generic/new_id
+	echo $DEV_UUID > /sys/bus/vmbus/drivers/hv_netvsc/unbind
+	echo $DEV_UUID > /sys/bus/vmbus/drivers/uio_hv_generic/bind
+
+.. Note::
+
+   The dpkd-devbind.py script can not be used since it only handles PCI devices.
+
+
+Prerequisites
+-------------
+
+The following prerequisites apply:
+
+*   Linux kernel support for UIO on vmbus is done with the uio_hv_generic driver.
+    Full support of multiple queues requires the 4.17 kernel. It is possible
+    to use the netvsc PMD with 4.16 kernel but it is limited to a single queue.