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

[Tian, Kevin]

> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Tuesday, January 25, 2022 1:44 AM
> 
> 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.
> 

Indeed!