smmu-related clarification

smmu-related clarification

[Jorge Pereira]

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Hi All,

I'm having some smmu-related issues, I need help.

So, in my use-case scenario I have two linux guests running in parallel - dom0 and domU-. I have to enable the smmu because I want to passthough devices to domU.

Would be great if you help me to clarify the following questions:

  *   if I enable SMMU, it will applies not only to domU but also to dma-capable devices assigned to dom0?
  *   Do I have to add all smmu-masters  of dom0 in device tree as well? Or since dom0 has 1:1 mapping I don't have to do anything?

Thanks,
Jorge



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Re: smmu-related clarification

[Bertrand Marquis]

Hi Jorge,

> On 19 Nov 2020, at 13:16, Jorge Pereira <jorge.pereira@nxp.com> wrote:
> 
> Hi All,
>  
> I’m having some smmu-related issues, I need help. 
>  
> So, in my use-case scenario I have two linux guests running in parallel – dom0 and domU-. I have to enable the smmu because I want to passthough devices to domU.
>  
> Would be great if you help me to clarify the following questions:  
> 	• if I enable SMMU, it will applies not only to domU but also to dma-capable devices assigned to dom0?

yes it will apply to all your domains.

> 	• Do I have to add all smmu-masters  of dom0 in device tree as well? Or since dom0 has 1:1 mapping I don’t have to do anything?

smmu is not only used for remapping but also to protect DMA accesses which means for dom0 it will use 1:1 mapping but will limit DMA to the memory accessible to dom0.
So you will need to add all required smmu information to all devices you need otherwise devices will be denied any DMA access.

Regards
Bertrand

>  
> Thanks,
> Jorge