RE: [PATCH 0/7] iommu cleanup and refactoring

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Monday, January 24, 2022 3:11 PM
> 
> Hi,
> 
> The guest pasid and aux-domain related code are dead code in current
> iommu subtree. As we have reached a consensus that all these features
> should be based on the new iommufd framework (which is under active
> development), the first part of this series removes and cleanups all
> the dead code.
> 
> The second part of this series refactors the iommu_domain by moving all
> domain-specific ops from iommu_ops to a new domain_ops. This makes an
> iommu_domain self-contained and represent the abstraction of an I/O
> translation table in the IOMMU subsystem. With different type of
> iommu_domain providing different set of ops, it's easier to support more
> types of I/O translation tables.

You may want to give more background on this end goal. In general there
are four IOPT types in iommufd discussions:

1) The one currently tracked by iommu_domain, with a map/unmap semantics
2) The one managed by mm and shared to iommu via sva_bind/unbind ops
3) The one managed by userspace and bound to iommu via iommufd (require nesting)
4) The one managed by KVM (e.g. EPT) and shared to iommu via a TBD interface

Currently only 1) and 2) are supported. 2) is supported via sva specific 
structures, tracked outside of iommu_domain.

Following current direction 3) and 4) will end up to have separate tracking
structures too (some existing bits for 3 are removed by this series).

And this series is preparatory for extending the domain concept to be a 
general object for all IOPT types. And it is one important design direction
to be aligned in the iommu community.

Thanks
Kevin