Re: [Xen-users] Does XEN on ARM support allocation for physical continuous memory on DOM0/U?

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-10-19 at 11:39 +0000, Tom Ting[äéå] wrote:
> Hi All
>  
> I am currently working on our platform using Kernel 4.1 / XEN 4.6 RC.
> We have question about how to allocate physical continuous memory.
> Iâve checked some documents and most of them claims IOMMU is a better
> solution, which is not support on our platform.
> Is there document or where should I check for these information??

For dom0 this is known as the "1:1 mapping".

This is the default for all platforms right now, not using a 1:1 mapping
for dom0 requires an IOMMU. This corresponds to
 xen/arch/arm/domain_build.c:dom0_11_mapping being set, which is always the
case today.

To do passthrough of devices which can do DMA to a domU an IOMMU is
required. I know that some people have hacked in a 1:1 mapping even for
domU, but this is not something we support. An alternative is to run the
drivers in dom0 and expose them to guests via a PV interface.

You've not said what your actual goal is so I don't know which of the above
is relevant to you.

Ian.

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