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

[Jason Gunthorpe]

On Mon, Jan 24, 2022 at 09:46:26AM +0000, Tian, Kevin wrote:
> > 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

Yes, at least from an iommufd perspective I'd like to see one struct
for all of these types, mainly so we can have a uniform alloc, attach
and detatch flow for all io page table types. 

If we want to use the iommu_domain, or make iommu_domain a sub-class
of a new struct, can be determined as we go along.

Regardless, I think this cleanup stands on its own. Moving the ops and
purging the dead code is clearly the right thing to do.

Thanks,
Jason