Re: [Xen-devel] [PATCH v6 01/14] iommu: introduce the concept of BFN...

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx]
> Sent: 07 September 2018 09:17
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; 'Jan Beulich'
> <JBeulich@xxxxxxxx>
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Julien Grall
> <julien.grall@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>; xen-
> devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Subject: RE: [Xen-devel] [PATCH v6 01/14] iommu: introduce the concept of
> BFN...
> 
> > From: Paul Durrant [mailto:Paul.Durrant@xxxxxxxxxx]
> > Sent: Friday, September 7, 2018 4:13 PM
> >
> > > -----Original Message-----
> > > From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> > > Sent: 07 September 2018 07:24
> > > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Kevin Tian
> > > <kevin.tian@xxxxxxxxx>
> > > Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Julien Grall
> > > <julien.grall@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>;
> xen-
> > > devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> > > Subject: RE: [Xen-devel] [PATCH v6 01/14] iommu: introduce the concept
> > of
> > > BFN...
> > >
> > > >>> On 07.09.18 at 03:47, <kevin.tian@xxxxxxxxx> wrote:
> > > >>  From: Paul Durrant [mailto:Paul.Durrant@xxxxxxxxxx]
> > > >> Sent: Thursday, September 6, 2018 10:54 PM
> > > >>
> > > >> > -----Original Message-----
> > > >> > From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> > > >> > Sent: 06 September 2018 14:13
> > > >> > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> > > >> > Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Julien
> > > Grall
> > > >> > <julien.grall@xxxxxxx>; Kevin Tian <kevin.tian@xxxxxxxxx>;
> Stefano
> > > >> > Stabellini <sstabellini@xxxxxxxxxx>; xen-devel <xen-
> > > >> > devel@xxxxxxxxxxxxxxxxxxxx>
> > > >> > Subject: RE: [Xen-devel] [PATCH v6 01/14] iommu: introduce the
> > > concept
> > > >> of
> > > >> > BFN...
> > > >> >
> > > >> > >>> On 06.09.18 at 12:36, <Paul.Durrant@xxxxxxxxxx> wrote:
> > > >> > >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> > > >> > >> Sent: 05 September 2018 10:39
> > > >> > >>
> > > >> > >> >>> On 05.09.18 at 11:13, <Paul.Durrant@xxxxxxxxxx> wrote:
> > > >> > >> > Personally I think 'bus address' is commonly enough used term
> > for
> > > >> > >> addresses
> > > >> > >> > used by devices for DMA. Indeed we have already
> > 'dev_bus_addr'
> > > in
> > > >> > the
> > > >> > >> grant
> > > >> > >> > map and unmap hypercalls. So baddr and bfn seem like ok
> > terms to
> > > >> me.
> > > >> > It's
> > > >> > >> > also not impossible to rename these later if they prove
> > > problematic.
> > > >> > >>
> > > >> > >> But that's the point - the names are problematic (to me): I
> > > >> permanently
> > > >> > >> have to remind myself that they do _not_ refer to the addresses
> > as
> > > >> > >> seen when accessing memory, but the ones going _into_ the
> > > IOMMU.
> > > >> > >
> > > >> > > Ok. Could we agree on 'IOFN' then? I think 'iova' and 'io address'
> > are
> > > >> also
> > > >> > > reasonably widely used terms to refer to address from a device's
> > PoV.
> > > >> I'd
> > > >> > > really like to unblock these early patches.
> > > >> >
> > > >> > Hmm, earlier I had indicated I'd prefer DFN (as this make clear
> > whose
> > > >> > view we are talking about). Kevin seemed to prefer DFN too, just
> with
> > > >> > a different association for D (which, as said, I consider 
> > > >> > unhelpful). So
> > > >> > is there a particular reason you're now suggesting IOFN
> nevertheless?
> > > >>
> > > >> It was the ambiguity and lack of agreement over the 'D' that made me
> > > think
> > > >> that the other alternative would be better.
> > > >> Kevin, would you be ok with 'IOFN'?
> > > >>
> > > >
> > > > My problem with DFN is when combining D with address then "device
> > > > address" is not very clear to me while interpreting D as DMA is also
> > > > not that clear from Jan's point.
> > >
> > > What about making its description mention both possible
> interpretations?
> > >
> >
> > I'm ok with DFN plus supporting text. Kevin, are you ok with that?
> >
> 
> sure

Ok. Decision made. I will re-work the patches.

  Paul

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