From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bruce Richardson <bruce.richardson@intel.com>
Subject: Re: [PATCH] doc: Clarify IOMMU usage with "uio-pci"
 kernel module
Date: Tue, 4 Sep 2018 11:06:26 +0100
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References: <1536051547-8797-1-git-send-email-tone.zhang@arm.com>
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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@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