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

  • To: Ian Campbell <ian.campbell@xxxxxxxxxx>, "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>
  • From: Tom Ting[äéå] <tom_ting@xxxxxxxxxxx>
  • Date: Tue, 20 Oct 2015 12:16:08 +0000
  • Accept-language: zh-TW, en-US
  • Authenticated-by:
  • Delivery-date: Tue, 20 Oct 2015 12:17:39 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>
  • Thread-index: AdEKYTFjq6HR93rOQJa6ojdoFUO9ogAf2J0AABQNLlA=
  • Thread-topic: [Xen-users] Does XEN on ARM support allocation for physical continuous memory on DOM0/U?

>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.
>> I've 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.

Hi Ian

Thanks for your information.
The thing we are actually doing is that we are planing to do is constructing 
three domains :
Dom0 : As small as possible
DomU_Android : Android System.
DomU_Function : handles some hardware specific function.

We want two DomU have no interference with each other and handle their own 
For Android system, memory such as ION / Framebuffer will need to be 
As you mentioned, if we want to solve the memory-contiguous problem on DomU, we 
have to hack through the domain-memory-allocation path right?
Could you tell us where is the location of DomU memory construction flow that 
we could do some modification?
Really thanks for your help.

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