Re: [PATCH RFC v2 02/13] iommufd: Overview documentation

David Gibson
2022-09-12T10:55:00Z

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On Fri, Sep 09, 2022 at 03:52:27PM -0300, Jason Gunthorpe wrote:
> On Wed, Sep 07, 2022 at 11:39:51AM +1000, David Gibson wrote:
>
> > > +expected to deprecate any proprietary IOMMU logic, if existing (e.g.
> >
> > I don't thing "propietary" is an accurate description. Maybe
> > "existing" or "bespoke?
>
> How about "internal"

> These drivers are eventually expected to deprecate any internal IOMMU
> logic, if existing (e.g. vfio_iommu_type1.c).

That works.

> > > +All user-visible objects are destroyed via the IOMMU_DESTROY uAPI.
> > > +
> > > +Linkage between user-visible objects and external kernel datastructures are
> > > +reflected by dotted line arrows below, with numbers referring to certain
> >
> > I'm a little bit confused by the reference to "dotted line arrows": I
> > only see one arrow style in the diagram.
>
> I think this means all the "dashed lines with arrows"
>
> How about "by the directed lines below"

Or simply "reflected by arrows below".

> > > +The iopt_pages is the center of the storage and motion of PFNs. Each iopt_pages
> > > +represents a logical linear array of full PFNs. PFNs are stored in a tiered
> > > +scheme:
> > > +
> > > + 1) iopt_pages::pinned_pfns xarray
> > > + 2) An iommu_domain
> > > + 3) The origin of the PFNs, i.e. the userspace pointer
> >
> > I can't follow what this "tiered scheme" is describing.
>
> Hum, I'm not sure how to address this.
>
> Is this better?
>
> 1) PFNs that have been "software accessed" stored in theiopt_pages::pinned_pfns
> xarray
> 2) PFNs stored inside the IOPTEs accessed through an iommu_domain
> 3) The origin of the PFNs, i.e. the userspace VA in a mm_struct

Hmm.. only slightly. What about:

Each opt_pages represents a logical linear array of full PFNs. The
PFNs are ultimately derived from userspave VAs via an mm_struct.
They are cached in .. <describe the pined_pfns and iommu_domain
data structures>

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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