[dpdk-dev] [PATCH] doc: Clarify IOMMU usage with "uio-pci" kernel module
Bruce Richardson
bruce.richardson at intel.com
Tue Sep 4 12:06:26 CEST 2018
On Tue, Sep 04, 2018 at 04:59:07PM +0800, tone.zhang wrote:
> When binding the devices used by DPDK to the "uio-pci" 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 configuration on both x86_64 and arm64
> systems.
>
> Signed-off-by: tone.zhang <tone.zhang at 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..8f9ec8f 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 for used DPDK bound to the ``uio-pci`` kernel module, please make
> + sure that the IOMMU is disabled. We can add ``intel_iommu=off`` or ``amd_iommu=off``
> + in ``GRUB_CMDLINE_LINUX`` in grub on x86_64 systems, or add ``iommu.passthrough=1``
> + on arm64 system.
> +
I think passthrough mode should work on x86 too. I remember running with
iommu=pt setting in the kernel in the past.
/Bruce
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