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Re: [Xen-devel] [PATCH] xen/arm: Let the IOMMU be accessible by Dom0 if forcibly disabled in Xen

On Thu, Aug 08, 2019 at 01:53:23PM +0300, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> Don't skip IOMMU nodes when creating DT for Dom0 if IOMMU has been
> forcibly disabled in bootargs (e.g. "iommu=0") in order to let
> the IOMMU be accessible by DOM0.
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> ---
> I have heard there is a "possible" case when the IOMMU could be accessible by 
> DOM0.
> So, I think, for this to work we need to create corresponding DT nodes in the 
> DT
> at least.

dom0 on ARM being an autotranslated guest I'm not sure how it's going
to program the DMA remapping in the iommu, since it doesn't know the
mfns of the memory it uses at all, hence I don't see the point in
exposing the hardware iommu to dom0 unless there's some emulation done
to make dom0 able to access it.

Thanks, Roger.

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