doc: warn about UIO not working with UEFI secure boot

Added notes to the documentation warning that if UEFI secure boot
is enabled the Linux kernel may disallow the use of UIO on the
system, and a suggested workaround of using the vfio-pci kernel
module instead of igb_uio or uio_pci_generic.

Signed-off-by: John McNamara <john.mcnamara@intel.com>

doc/guides/faq/faq.rst

@@ -222,3 +222,10 @@ How can hugepage-backed memory be shared among multiple processes?
 ------------------------------------------------------------------
 
 See the Primary and Secondary examples in the :ref:`multi-process sample application <multi_process_app>`.
+
+
+Why can't my application receive packets on my system with UEFI Secure Boot enabled?
+------------------------------------------------------------------------------------
+
+If UEFI secure boot is enabled, the Linux kernel may disallow the use of UIO on the system.
+Therefore, devices for use by DPDK should be bound to the ``vfio-pci`` kernel module rather than ``igb_uio`` or ``uio_pci_generic``.

doc/guides/linux_gsg/linux_drivers.rst

@@ -67,6 +67,13 @@ be loaded as shown below:
     For some devices which lack support for legacy interrupts, e.g. virtual function
     (VF) devices, the ``igb_uio`` module may be needed in place of ``uio_pci_generic``.
 
+.. note::
+
+   If UEFI secure boot is enabled, the Linux kernel may disallow the use of
+   UIO on the system. Therefore, devices for use by DPDK should be bound to the
+   ``vfio-pci`` kernel module rather than ``igb_uio`` or ``uio_pci_generic``.
+   For more details see :ref:`linux_gsg_binding_kernel` below.
+
 Since DPDK release 1.7 onward provides VFIO support, use of UIO is optional
 for platforms that support using VFIO.
 

doc/guides/linux_gsg/sys_reqs.rst

@@ -47,6 +47,13 @@ and high performance of small packets, BIOS setting changes may be needed.
 Consult the section on :ref:`Enabling Additional Functionality <Enabling_Additional_Functionality>`
 for more information on the required changes.
 
+.. note::
+
+   If UEFI secure boot is enabled, the Linux kernel may disallow the use of
+   UIO on the system. Therefore, devices for use by DPDK should be bound to the
+   ``vfio-pci`` kernel module rather than ``igb_uio`` or ``uio_pci_generic``.
+   For more details see :ref:`linux_gsg_binding_kernel`.
+
 Compilation of the DPDK
 -----------------------