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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