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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----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?

  Paul

  

> Jan
> 


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