Re: [Xen-devel] [PATCH 2/4] iommu: generalize iommu_inclusive_mapping

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.07.18 at 10:37, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Roger Pau Monne
>> Sent: 31 July 2018 09:34
>> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Kevin Tian <kevin.tian@xxxxxxxxx>;
>> Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>;
>> George Dunlap <George.Dunlap@xxxxxxxxxx>; Andrew Cooper
>> <Andrew.Cooper3@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; Tim
>> (Xen.org) <tim@xxxxxxx>; Julien Grall <julien.grall@xxxxxxx>; Jan Beulich
>> <jbeulich@xxxxxxxx>
>> Subject: Re: [Xen-devel] [PATCH 2/4] iommu: generalize
>> iommu_inclusive_mapping
>> 
>> On Tue, Jul 31, 2018 at 09:27:03AM +0100, Paul Durrant wrote:
>> > > -----Original Message-----
>> > > From: Roger Pau Monne
>> > > Sent: 31 July 2018 09:16
>> > > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
>> > > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Kevin Tian <kevin.tian@xxxxxxxxx>;
>> > > Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu
>> <wei.liu2@xxxxxxxxxx>;
>> > > George Dunlap <George.Dunlap@xxxxxxxxxx>; Andrew Cooper
>> > > <Andrew.Cooper3@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>;
>> Tim
>> > > (Xen.org) <tim@xxxxxxx>; Julien Grall <julien.grall@xxxxxxx>; Jan
>> Beulich
>> > > <jbeulich@xxxxxxxx>
>> > > Subject: Re: [Xen-devel] [PATCH 2/4] iommu: generalize
>> > > iommu_inclusive_mapping
>> > >
>> > > On Tue, Jul 31, 2018 at 08:18:36AM +0100, Paul Durrant wrote:
>> > > > > -----Original Message-----
>> > > > > From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx]
>> On
>> > > Behalf
>> > > > > Of Roger Pau Monne
>> > > > > Sent: 27 July 2018 16:32
>> > > > > To: xen-devel@xxxxxxxxxxxxxxxxxxxx 
>> > > > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>; Stefano Stabellini
>> > > > > <sstabellini@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; George
>> Dunlap
>> > > > > <George.Dunlap@xxxxxxxxxx>; Andrew Cooper
>> > > > > <Andrew.Cooper3@xxxxxxxxxx>; Ian Jackson
>> <Ian.Jackson@xxxxxxxxxx>;
>> > > Tim
>> > > > > (Xen.org) <tim@xxxxxxx>; Julien Grall <julien.grall@xxxxxxx>; Jan
>> > > Beulich
>> > > > > <jbeulich@xxxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>
>> > > > > Subject: [Xen-devel] [PATCH 2/4] iommu: generalize
>> > > > > iommu_inclusive_mapping
>> > > > >
>> > > > > Introduce a new iommu=inclusive generic option that supersedes
>> > > > > iommu_inclusive_mapping. This should be a non-functional change
>> on
>> > > > > Intel hardware, while AMD hardware will gain the same functionality
>> of
>> > > > > mapping almost everything below the 4GB boundary.
>> > > > >
>> > > > > Note that is a noop for ARM hardware.
>> > > > >
>> > > > > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> > > > > ---
>> > > > > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> > > > > Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
>> > > > > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>> > > > > Cc: Jan Beulich <jbeulich@xxxxxxxx>
>> > > > > Cc: Julien Grall <julien.grall@xxxxxxx>
>> > > > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> > > > > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>> > > > > Cc: Tim Deegan <tim@xxxxxxx>
>> > > > > Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
>> > > > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
>> > > > > ---
>> > > > >  docs/misc/xen-command-line.markdown   | 14 ++++++
>> > > > >  xen/drivers/passthrough/arm/iommu.c   |  4 ++
>> > > > >  xen/drivers/passthrough/iommu.c       |  6 +++
>> > > > >  xen/drivers/passthrough/vtd/extern.h  |  2 -
>> > > > >  xen/drivers/passthrough/vtd/iommu.c   |  6 ---
>> > > > >  xen/drivers/passthrough/vtd/x86/vtd.c | 66 +------------------------
>> > > > >  xen/drivers/passthrough/x86/iommu.c   | 70
>> > > > > +++++++++++++++++++++++++++
>> > > > >  xen/include/xen/iommu.h               |  2 +
>> > > > >  8 files changed, 97 insertions(+), 73 deletions(-)
>> > > > >
>> > > > > diff --git a/docs/misc/xen-command-line.markdown
>> b/docs/misc/xen-
>> > > > > command-line.markdown
>> > > > > index 65b4754418..91a8bfc9a6 100644
>> > > > > --- a/docs/misc/xen-command-line.markdown
>> > > > > +++ b/docs/misc/xen-command-line.markdown
>> > > > > @@ -1198,6 +1198,17 @@ detection of systems known to misbehave
>> > > upon
>> > > > > accesses to that port.
>> > > > >
>> > > > >  >> Enable IOMMU debugging code (implies `verbose`).
>> > > > >
>> > > > > +> `inclusive`
>> > > >
>> > > > This is a dom0 (or hwdom) specific setting so perhaps dom0-inclusive?
>> > > >
>> > > > Actually the dom0 iommu options are starting to get unwieldy as they
>> are
>> > > conflated with the general host iommu options so I think it may be
>> > > worthwhile splitting things out into a separate 'dom0-iommu=' top level
>> > > parameter at this stage. (My reasons are slightly selfish as I intend to 
> add
>> > > another dom0 iommu option to give it just reserved regions, to avoid
>> > > unnecessary set-up if we know it will be using PV-IOMMU).
>> > >
>> > > Mapping just the reserved regions is what I actually do for PVH with
>> > > iommu=inclusive (patch 4/4), so maybe it would make sense to speak
>> about
>> > > the
>> > > naming here in order to use the same naming for PV and PVH.
>> > >
>> > > TBH I don't really like the dom0- prefix, the command line iommu
>> > > options either apply to all domains or Dom0 only, having
>> > > domu-inclusive for example makes no sense IMO.
>> >
>> > No, I think there are some options that you may want to apply to dom0
>> only, but these are more like the dom0_mem or dom0_max_vpus options.
>> Particularly, the inclusive option is probably something that is only 
>> desirable
>> for dom0. Clearly dom0-passthrough and dom0-strict are already defined to
>> relate to dom0 only, and options such as 'reserved' should only be specific 
>> on
>> the command line in relation to dom0 IMO. For other domains such an option
>> should be specified via xl.cfg.
>> 
>> Yes, we already have a bunch of those, so then I think dom0-inclusive
>> and dom0-reserved would be appropriate?
>> 
>> dom0-inclusive-mapping or dom0-reserved-mapping seems too long.
> 
> Yes, those names are ok, but I still think it better in the long run if we 
> have something like:
> 
> dom0_iommu=[inclusive,][reserved,][strict,][none,][relaxed]
> 
> where relaxed is the default and 'none' (I think) is equivalent to the 
> current iommu=dom0-passthrough.

Or, along the lines of the other reply just sent, e.g.

dom0=pvh,iommu:inclusive;reserved,shadow

But perhaps the difference between , and ; gets too confusing then.

Jan


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