ceph/src/spdk/dpdk/doc/guides/linux_gsg/linux_drivers.rst

   1 ..  SPDX-License-Identifier: BSD-3-Clause
   2     Copyright(c) 2010-2015 Intel Corporation.
   3     Copyright 2017 Mellanox Technologies, Ltd
   4     All rights reserved.
   5
   6 .. _linux_gsg_linux_drivers:
   7
   8 Linux Drivers
   9 =============
  10
  11 Different PMDs may require different kernel drivers in order to work properly.
  12 Depends on the PMD being used, a corresponding kernel driver should be load
  13 and bind to the network ports.
  14
  15 UIO
  16 ---
  17
  18 A small kernel module to set up the device, map device memory to user-space and register interrupts.
  19 In many cases, the standard ``uio_pci_generic`` module included in the Linux kernel
  20 can provide the uio capability. This module can be loaded using the command:
  21
  22 .. code-block:: console
  23
  24     sudo modprobe uio_pci_generic
  25
  26 .. note::
  27
  28     ``uio_pci_generic`` module doesn't support the creation of virtual functions.
  29
  30 As an alternative to the ``uio_pci_generic``, the DPDK also includes the igb_uio
  31 module which can be found in the kmod subdirectory referred to above. It can
  32 be loaded as shown below:
  33
  34 .. code-block:: console
  35
  36     sudo modprobe uio
  37     sudo insmod kmod/igb_uio.ko
  38
  39 .. note::
  40
  41     For some devices which lack support for legacy interrupts, e.g. virtual function
  42     (VF) devices, the ``igb_uio`` module may be needed in place of ``uio_pci_generic``.
  43
  44 .. note::
  45
  46    If UEFI secure boot is enabled, the Linux kernel may disallow the use of
  47    UIO on the system. Therefore, devices for use by DPDK should be bound to the
  48    ``vfio-pci`` kernel module rather than ``igb_uio`` or ``uio_pci_generic``.
  49    For more details see :ref:`linux_gsg_binding_kernel` below.
  50
  51 .. note::
  52
  53    If the devices used for DPDK are bound to the ``uio_pci_generic`` kernel module,
  54    please make sure that the IOMMU is disabled or passthrough. One can add
  55    ``intel_iommu=off`` or ``amd_iommu=off`` or ``intel_iommu=on iommu=pt``in GRUB
  56    command line on x86_64 systems, or add ``iommu.passthrough=1`` on arm64 system.
  57
  58 Since DPDK release 1.7 onward provides VFIO support, use of UIO is optional
  59 for platforms that support using VFIO.
  60
  61 VFIO
  62 ----
  63
  64 A more robust and secure driver in compare to the ``UIO``, relying on IOMMU protection.
  65 To make use of VFIO, the ``vfio-pci`` module must be loaded:
  66
  67 .. code-block:: console
  68
  69     sudo modprobe vfio-pci
  70
  71 Note that in order to use VFIO, your kernel must support it.
  72 VFIO kernel modules have been included in the Linux kernel since version 3.6.0 and are usually present by default,
  73 however please consult your distributions documentation to make sure that is the case.
  74
  75 Also, to use VFIO, both kernel and BIOS must support and be configured to use IO virtualization (such as Intel® VT-d).
  76
  77 .. note::
  78
  79     ``vfio-pci`` module doesn't support the creation of virtual functions.
  80
  81 For proper operation of VFIO when running DPDK applications as a non-privileged user, correct permissions should also be set up.
  82 This can be done by using the DPDK setup script (called dpdk-setup.sh and located in the usertools directory).
  83
  84 .. note::
  85
  86     VFIO can be used without IOMMU. While this is just as unsafe as using UIO, it does make it possible for the user to keep the degree of device access and programming that VFIO has, in situations where IOMMU is not available.
  87
  88 .. _bifurcated_driver:
  89
  90 Bifurcated Driver
  91 -----------------
  92
  93 PMDs which use the bifurcated driver co-exists with the device kernel driver.
  94 On such model the NIC is controlled by the kernel, while the data
  95 path is performed by the PMD directly on top of the device.
  96
  97 Such model has the following benefits:
  98
  99  - It is secure and robust, as the memory management and isolation
 100    is done by the kernel.
 101  - It enables the user to use legacy linux tools such as ``ethtool`` or
 102    ``ifconfig`` while running DPDK application on the same network ports.
 103  - It enables the DPDK application to filter only part of the traffic,
 104    while the rest will be directed and handled by the kernel driver.
 105    The flow bifurcation is performed by the NIC hardware.
 106    As an example, using :ref:`flow_isolated_mode` allows to choose
 107    strictly what is received in DPDK.
 108
 109 More about the bifurcated driver can be found in
 110 `Mellanox Bifurcated DPDK PMD
 111 <https://dpdksummit.com/Archive/pdf/2016Userspace/Day02-Session04-RonyEfraim-Userspace2016.pdf>`__.
 112
 113 .. _linux_gsg_binding_kernel:
 114
 115 Binding and Unbinding Network Ports to/from the Kernel Modules
 116 --------------------------------------------------------------
 117
 118 .. note::
 119
 120     PMDs Which use the bifurcated driver should not be unbind from their kernel drivers. this section is for PMDs which use the UIO or VFIO drivers.
 121
 122 As of release 1.4, DPDK applications no longer automatically unbind all supported network ports from the kernel driver in use.
 123 Instead, in case the PMD being used use the UIO or VFIO drivers, all ports that are to be used by an DPDK application must be bound to the
 124 ``uio_pci_generic``, ``igb_uio`` or ``vfio-pci`` module before the application is run.
 125 For such PMDs, any network ports under Linux* control will be ignored and cannot be used by the application.
 126
 127 To bind ports to the ``uio_pci_generic``, ``igb_uio`` or ``vfio-pci`` module for DPDK use,
 128 and then subsequently return ports to Linux* control,
 129 a utility script called dpdk-devbind.py is provided in the usertools subdirectory.
 130 This utility can be used to provide a view of the current state of the network ports on the system,
 131 and to bind and unbind those ports from the different kernel modules, including the uio and vfio modules.
 132 The following are some examples of how the script can be used.
 133 A full description of the script and its parameters can be obtained by calling the script with the ``--help`` or ``--usage`` options.
 134 Note that the uio or vfio kernel modules to be used, should be loaded into the kernel before
 135 running the ``dpdk-devbind.py`` script.
 136
 137 .. warning::
 138
 139     Due to the way VFIO works, there are certain limitations to which devices can be used with VFIO.
 140     Mainly it comes down to how IOMMU groups work.
 141     Any Virtual Function device can be used with VFIO on its own, but physical devices will require either all ports bound to VFIO,
 142     or some of them bound to VFIO while others not being bound to anything at all.
 143
 144     If your device is behind a PCI-to-PCI bridge, the bridge will then be part of the IOMMU group in which your device is in.
 145     Therefore, the bridge driver should also be unbound from the bridge PCI device for VFIO to work with devices behind the bridge.
 146
 147 .. warning::
 148
 149     While any user can run the dpdk-devbind.py script to view the status of the network ports,
 150     binding or unbinding network ports requires root privileges.
 151
 152 To see the status of all network ports on the system:
 153
 154 .. code-block:: console
 155
 156     ./usertools/dpdk-devbind.py --status
 157
 158     Network devices using DPDK-compatible driver
 159     ============================================
 160     0000:82:00.0 '82599EB 10-GbE NIC' drv=uio_pci_generic unused=ixgbe
 161     0000:82:00.1 '82599EB 10-GbE NIC' drv=uio_pci_generic unused=ixgbe
 162
 163     Network devices using kernel driver
 164     ===================================
 165     0000:04:00.0 'I350 1-GbE NIC' if=em0  drv=igb unused=uio_pci_generic *Active*
 166     0000:04:00.1 'I350 1-GbE NIC' if=eth1 drv=igb unused=uio_pci_generic
 167     0000:04:00.2 'I350 1-GbE NIC' if=eth2 drv=igb unused=uio_pci_generic
 168     0000:04:00.3 'I350 1-GbE NIC' if=eth3 drv=igb unused=uio_pci_generic
 169
 170     Other network devices
 171     =====================
 172     <none>
 173
 174 To bind device ``eth1``,``04:00.1``, to the ``uio_pci_generic`` driver:
 175
 176 .. code-block:: console
 177
 178     ./usertools/dpdk-devbind.py --bind=uio_pci_generic 04:00.1
 179
 180 or, alternatively,
 181
 182 .. code-block:: console
 183
 184     ./usertools/dpdk-devbind.py --bind=uio_pci_generic eth1
 185
 186 To restore device ``82:00.0`` to its original kernel binding:
 187
 188 .. code-block:: console
 189
 190     ./usertools/dpdk-devbind.py --bind=ixgbe 82:00.0