[PATCH v2 5/9] doc: emphasise VFIO over UIO-based modules in GSG

[Bruce Richardson <bruce.richardson@intel.com>]

VFIO is to be strongly preferred over uio-based modules, so update our
text and examples to only refer to vfio, giving an initial reference at
the start to uio as a fallback option.

Cc: stable@dpdk.org

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 doc/guides/linux_gsg/linux_drivers.rst | 47 +++++++++++++++-----------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/doc/guides/linux_gsg/linux_drivers.rst b/doc/guides/linux_gsg/linux_drivers.rst
index b93feae7a1..bd649db929 100644
--- a/doc/guides/linux_gsg/linux_drivers.rst
+++ b/doc/guides/linux_gsg/linux_drivers.rst
@@ -25,14 +25,18 @@ Binding and Unbinding Network Ports to/from the Kernel Modules
    This section is for PMDs which use the UIO or VFIO drivers.
    See :ref:`bifurcated_driver` section for more details.

-As of release 1.4, DPDK applications no longer automatically unbind all supported network ports from the kernel driver in use.
-Instead, in case the PMD being used use the VFIO or UIO drivers,
-all ports that are to be used by a DPDK application must be bound to
-the ``vfio-pci``, ``uio_pci_generic``, or ``igb_uio`` module
-before the application is run.
-For such PMDs, any network ports under Linux* control will be ignored and cannot be used by the application.
-
-To bind ports to the ``vfio-pci``, ``uio_pci_generic`` or ``igb_uio`` module
+.. note::
+
+   It is recommended that ``vfio-pci`` be used as the kernel module for DPDK-bound ports in all cases.
+   If an IOMMU is unavailable, the ``vfio-pci`` can be used in :ref:`no-iommu<vfio_noiommu>` mode.
+   If, for some reason, vfio is unavailable, then UIO-based modules, ``igb_uio`` and ``uio_pci_generic`` may be used.
+   See section :ref:`uio` for details.
+
+Most devices require that the hardware to be used by DPDK be unbound from the kernel driver it uses,
+and instead be bound to the ``vfio-pci`` kernel module before the application is run.
+For such PMDs, any network ports or other hardware under Linux* control will be ignored and cannot be used by the application.
+
+To bind ports to the ``vfio-pci`` module
 for DPDK use, or to return ports to Linux control,
 a utility script called ``dpdk-devbind.py`` is provided in the ``usertools`` subdirectory.
 This utility can be used to provide a view of the current state of the network ports on the system,
@@ -72,37 +76,38 @@ To see the status of all network ports on the system:

     Network devices using DPDK-compatible driver
     ============================================
-    0000:82:00.0 '82599EB 10-GbE NIC' drv=uio_pci_generic unused=ixgbe
-    0000:82:00.1 '82599EB 10-GbE NIC' drv=uio_pci_generic unused=ixgbe
+    0000:82:00.0 '82599EB 10-GbE NIC' drv=vfio-pci unused=ixgbe
+    0000:82:00.1 '82599EB 10-GbE NIC' drv=vfio-pci unused=ixgbe

     Network devices using kernel driver
     ===================================
-    0000:04:00.0 'I350 1-GbE NIC' if=em0  drv=igb unused=uio_pci_generic *Active*
-    0000:04:00.1 'I350 1-GbE NIC' if=eth1 drv=igb unused=uio_pci_generic
-    0000:04:00.2 'I350 1-GbE NIC' if=eth2 drv=igb unused=uio_pci_generic
-    0000:04:00.3 'I350 1-GbE NIC' if=eth3 drv=igb unused=uio_pci_generic
+    0000:04:00.0 'I350 1-GbE NIC' if=em0  drv=igb unused=vfio-pci *Active*
+    0000:04:00.1 'I350 1-GbE NIC' if=eth1 drv=igb unused=vfio-pci
+    0000:04:00.2 'I350 1-GbE NIC' if=eth2 drv=igb unused=vfio-pci
+    0000:04:00.3 'I350 1-GbE NIC' if=eth3 drv=igb unused=vfio-pci

     Other network devices
     =====================
     <none>

-To bind device ``eth1``,``04:00.1``, to the ``uio_pci_generic`` driver:
+To bind device ``eth1``,``04:00.1``, to the ``vfio-pci`` driver:

 .. code-block:: console

-    ./usertools/dpdk-devbind.py --bind=uio_pci_generic 04:00.1
+    ./usertools/dpdk-devbind.py --bind=vfio-pci 04:00.1

 or, alternatively,

 .. code-block:: console

-    ./usertools/dpdk-devbind.py --bind=uio_pci_generic eth1
+    ./usertools/dpdk-devbind.py --bind=vfio-pci eth1

-To restore device ``82:00.0`` to its original kernel binding:
+When specifying device ids, wildcards can be used for the final part of the address.
+To restore device ``82:00.0`` and ``82:00.1`` to their original kernel binding:

 .. code-block:: console

-    ./usertools/dpdk-devbind.py --bind=ixgbe 82:00.0
+    ./usertools/dpdk-devbind.py --bind=ixgbe 82:00.*

 VFIO
 ----
@@ -210,6 +215,8 @@ to use IO virtualization (such as Intel\ |reg| VT-d).
 For proper operation of VFIO when running DPDK applications as a non-privileged user, correct permissions should also be set up.
 For more information, please refer to :ref:`Running_Without_Root_Privileges`.

+.. _vfio_noiommu:
+
 VFIO no-IOMMU mode
 ------------------

@@ -240,6 +247,8 @@ After that, VFIO can be used with hardware devices as usual.
    to keep the degree of device access and programming that VFIO has,
    in situations where IOMMU is not available.

+.. _uio:
+
 UIO
 ---

--
2.32.0