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To: Alejandro Lucero <alejandro.lucero@netronome.com>, dev@dpdk.org
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From: Ferruh Yigit <ferruh.yigit@intel.com>
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Date: Tue, 7 Feb 2017 15:59:20 +0000
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Subject: Re: [dpdk-dev] [PATCH] igb_uio: map dummy dma forcing iommu domain
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Hi Alejandro,

On 1/18/2017 12:27 PM, Alejandro Lucero wrote:
> For using a DPDK app when iommu is enabled, it requires to
> add iommu=pt to the kernel command line. But using igb_uio driver
> makes DMAR errors because the device has not an IOMMU domain.

Please help to understand the scope of the problem,

1- How can you re-produce the problem?

2- What happens get DMAR errors, is it prevents device work or some
annoying error messages?

3- Can you please share the error messages?


> 
> Since kernel 3.15, iommu=pt requires to use the internal kernel
> DMA API for attaching the device to the IOMMU 1:1 mapping, aka
> si_domain. Previous versions did attach the device to that
> domain when intel iommu notifier was called.

Again, what is not working since 3.15?

> 
> This is not a problem if the driver does later some call to the
> DMA API because the mapping can be done then. But DPDK apps do
> not use that DMA API at all.

Is this same/similar with: http://dpdk.org/dev/patchwork/patch/12654/

> 
> Doing this dma map and unmap is harmless even when iommu is not
> enabled at all.
> 
> Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
<...>

Thanks,
ferruh