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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----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.

  Paul

> 
> Thanks, Roger.

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