Re: [Xen-devel] Xen ARM smmu questions

[Jinch <jinchen1227@xxxxxx>]

Thank you for your reply,
I’m just researching the implementation of the SMMU driver in Xen and dom0 
kernel.
If my board has SMMU of arm,mmu-500, do you mean that the Xen use the stage 2 
of it and the dom0 kernel use stage1?
And if I want to passthrough some device that use SMMU to domu, how the SMMU 
working in Xen and the domu kernel?

> 在 2019年3月12日，下午7:42，Julien Grall <julien.grall@xxxxxxx> 写道：
> 
> 
> On 3/12/19 8:58 AM, jinchen wrote:
>> Hello xen-devel,
> 
> Hello,
> 
>> I'm reading the code of xen arm smmu in drivers/passthrough/arm, and I have 
>> some questions that confused me.
>> I think if the board use SMMU, xen will take charge of it before dom0 boot, 
>> and will not pass the node of SMMU to dom0 in device tree,
>> so my question is how dom0 use SMMU? or can dom0 use SMMU? What dom0 use if 
>> it wants to use IOMMU?
>> What about domU? The SMMU could be passed to domU?
> 
> Some SMMU are able to provide Stage 1 (Guest VA to Guest PA) and Stage 2 
> (Guest PA to Host PA) support. In the current configuration, Xen will use the 
> Stage 2 part to isolate device passthrough. Stage 1 is not supported.
> 
> If you wanted a guest to use the SMMU, you would either need to provide Stage 
> 1 support (requires HW support) or a PV IOMMU.
> 
> Alternatively, you might be able to give the SMMU to Dom0. I haven't explored 
> it so far. Do you have a use case for using the IOMMU in guest?
> 
> Cheers,
> 
> -- 
> Julien Grall
> 




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