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diff --git a/src/spdk/dpdk/doc/guides/nics/netvsc.rst b/src/spdk/dpdk/doc/guides/nics/netvsc.rst new file mode 100644 index 000000000..6dbb9a551 --- /dev/null +++ b/src/spdk/dpdk/doc/guides/nics/netvsc.rst @@ -0,0 +1,118 @@ +.. 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 interrupts. Link state change + callback is done via change events in the packet ring. + +* The maximum number of queues is limited by the host (currently 64). + When used with 4.16 kernel only a single queue is available. + +* This driver supports SR-IOV network acceleration. + If SR-IOV is enabled then the driver will transparently manage the interface, + and send and receive packets using the VF path. + The VDEV_NETVSC and FAILSAFE drivers are *not* used when using netvsc PMD. + +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 dpdk-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. + + +Netvsc PMD arguments +-------------------- + +The user can specify below argument in devargs. + +#. ``latency``: + + A netvsc device uses a mailbox page to indicate to the host that there + is something in the transmit queue. The host scans this page at a + periodic interval. This parameter allows adjusting the value that + is used by the host. Smaller values improve transmit latency, and larger + values save CPU cycles. This parameter is in microseconds. + If the value is too large or too small it will be + ignored by the host. (Default: 50) |