doc: clarify IOMMU disabling for uio_pci_generic

If the devices used for DPDK are bound to the "uio_pci_generic" kernel
module, the IOMMU should be disabled in order not to break the IO
transmission because of the virtual / physical address mapping.

The patch clarifies the IOMMU configurations on both x86_64 and arm64
systems.

Signed-off-by: Tone Zhang <tone.zhang@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Rami Rosen <roszenrami@gmail.com>
Acked-by: Gavin Hu <gavin.hu@arm.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Luca Boccassi <bluca@debian.org>

diff --git a/doc/guides/linux_gsg/linux_drivers.rst b/doc/guides/linux_gsg/linux_drivers.rst
index 371a817..8da6a31 100644 (file)
--- a/doc/guides/linux_gsg/linux_drivers.rst
+++ b/doc/guides/linux_gsg/linux_drivers.rst
@@ -48,6 +48,13 @@ be loaded as shown below:
    ``vfio-pci`` kernel module rather than ``igb_uio`` or ``uio_pci_generic``.
    For more details see :ref:`linux_gsg_binding_kernel` below.
 
+.. note::
+
+   If the devices used for DPDK are bound to the ``uio_pci_generic`` kernel module,
+   please make sure that the IOMMU is disabled or passthrough. One can add
+   ``intel_iommu=off`` or ``amd_iommu=off`` or ``intel_iommu=on iommu=pt``in GRUB
+   command line on x86_64 systems, or add ``iommu.passthrough=1`` on arm64 system.
+
 Since DPDK release 1.7 onward provides VFIO support, use of UIO is optional
 for platforms that support using VFIO.