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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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?

Jan



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