Re: [dpdk-dev] [PATCH v3] doc: Clarify IOMMU usage with "uio_pci_generic" kernel module

["Tone Zhang (Arm Technology China)" <Tone.Zhang@arm.com>]

Hello Bruce, Luca, Rami and Stephen,

Could you please help to review the change? 

Any comments are welcome.

Thanks a lot!

Br,
Tone

-----Original Message-----
From: dev <dev-bounces@dpdk.org> On Behalf Of tone.zhang
Sent: Wednesday, September 5, 2018 1:18 PM
To: dev@dpdk.org
Cc: Gavin Hu (Arm Technology China) <Gavin.Hu@arm.com>; bruce.richardson@intel.com; bluca@debian.org; roszenrami@gmail.com; nd <nd@arm.com>
Subject: [dpdk-dev] [PATCH v3] doc: Clarify IOMMU usage with "uio_pci_generic" kernel module

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>
---
 doc/guides/linux_gsg/linux_drivers.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/doc/guides/linux_gsg/linux_drivers.rst b/doc/guides/linux_gsg/linux_drivers.rst
index 371a817..b46fc6a 100644
--- 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. One can add ``intel_iommu=off`` or
+   ``intel_iommu=pt`` or ``amd_iommu=off`` 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.
 
--
2.7.4