Re: [Xen-devel] Driver domain on ARM questions

[Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>]

Hi Stefano,

Thanks a lot for your answers.

Regards,
Andrii

On Wed, Oct 15, 2014 at 4:48 PM, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Wed, 15 Oct 2014, Andrii Tseglytskyi wrote:
>> Hi,
>>
>> Can someone clarify the following questions:
>>
>> - is any special support required in Xen code to implement driver
>> domain on ARM ?
>
> Not particularly, but you need to be able to assign the device to the
> driver domain so the device needs to be behind an SMMU.
>
>
>> - is it possible to have one to one memory mapping in dom0 and driver
>> domain simultaneously ?
>
> We would want to avoid the 1:1 mapping in driver domains, so this is why
> we need the device to be behind an SMMU.
>
>
>> - if answer to previous one is NO, how can I make DMA working in driver 
>> domain ?
>
> The best and more performant option is to use an SMMU.
> Otherwise you can:
>
> - use XENMEM_exchange to make a guest buffer contiguous in machine
> memory space and bounce all the dma requests on the buffer using
> swiotlb-xen. It is not going to have great performances but it should
> work well.
>
> - use the 1:1 hack in the driver domain
>
>
>> I found only high level concepts:
>>
>> http://events.linuxfoundation.org/sites/events/files/slides/alsf13_stabellini.pdf
>> http://pdub.net/proj/usenix08boston/xen_drive/resources/xensummit/slides/14_SangBumSuh.pdf
>>
>> Thank you for any info, useful links or so.
>>
>> Regards,
>> Andrii
>>
>> --
>>
>> Andrii Tseglytskyi | Embedded Dev
>> GlobalLogic
>> www.globallogic.com
>>



-- 

Andrii Tseglytskyi | Embedded Dev
GlobalLogic
www.globallogic.com

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