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From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jason Gunthorpe <jgg@nvidia.com>,
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        "Raj, Ashok" <ashok.raj@intel.com>,
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CC:     Alex Williamson <alex.williamson@redhat.com>,
        Eric Auger <eric.auger@redhat.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
        "Pan, Jacob jun" <jacob.jun.pan@intel.com>,
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        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 0/7] iommu cleanup and refactoring
Thread-Topic: [PATCH 0/7] iommu cleanup and refactoring
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Date:   Mon, 24 Jan 2022 09:46:26 +0000
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> From: Lu Baolu <baolu.lu@linux.intel.com>
> Sent: Monday, January 24, 2022 3:11 PM
>=20
> Hi,
>=20
> 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.
>=20
> 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 nes=
ting)
4) The one managed by KVM (e.g. EPT) and shared to iommu via a TBD interfac=
e

Currently only 1) and 2) are supported. 2) is supported via sva specific=20
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=20
general object for all IOPT types. And it is one important design direction
to be aligned in the iommu community.

Thanks
Kevin