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Re: [Xen-devel] [PATCH for 4.6 13/13] xen/iommu: smmu: Add Xen specific code to be able to use the driver

On 18/02/15 11:52 pm, Julien Grall wrote:

On 18/02/2015 17:30, Jaggi, Manish wrote:
[manish] There are general comments on the data structures
(a) I don't see a use case where for same domain (VM) there would be different context banks , so linked list may not be required.

I guess you mean the list in arm_smmu_xen_domain? All the devices pass-through to a domain may not be protected by the same SMMU. Therefore the context banks are different.
you are right. For each smmu the context bank instance for a xen domain is duplicated with just a change in context bank id. I was thinking can it be minimized.

Also, for now a context is allocated per-device. It should be rework to share the context between multiple device protected by the same SMMU and pass-through to the same domain.
Yes, this is exactly I an doing at my end.

(b) Also iommu group may not be relevant for the same reason.
I am curious to find the use cases.

The iommu_group is used to store the configuration of the device protected by an SMMU (i.e the stream ids associated to this domain).

I'm a bit surprised that you think they are not useful...
How do we create an iommu_group in xen ? AFAIK an iommu group is a vfio group in linux which is assigned to a a VM.
lkvm run -m 512 -k home/Image ...  --vfio-groups=48, 51

For Xen There are 2 ways of attaching devices using xl pci-attach or in domU cfg file. Should they create different iommu_groups ?


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