Re: [Xen-devel] IOREQ server on Arm

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 26 September 2018 12:57
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>; Andrew Cooper
> <Andrew.Cooper3@xxxxxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>;
> Stefano Stabellini <sstabellini@xxxxxxxxxx>; xen-devel <xen-
> devel@xxxxxxxxxxxxxxxxxxxx>
> Subject: RE: IOREQ server on Arm
> 
> >>> On 26.09.18 at 13:02, <Paul.Durrant@xxxxxxxxxx> wrote:
> > --- a/xen/common/memory.c
> > +++ b/xen/common/memory.c
> > @@ -1105,8 +1105,11 @@ static int acquire_resource(
> >
> >          for ( i = 0; !rc && i < xmar.nr_frames; i++ )
> >          {
> > -            rc = set_foreign_p2m_entry(currd, gfn_list[i],
> > -                                       _mfn(mfn_list[i]));
> > +            rc = (xmar.flags & XENMEM_rsrc_acq_caller_owned) ?
> > +                guest_physmap_add_entry(currd, gfn_list[i],
> > +                                        _mfn(mfn_list[i]), 0,
> p2m_ram_rw) :
> > +                set_foreign_p2m_entry(currd, gfn_list[i],
> > +                                      _mfn(mfn_list[i]));
> >              /* rc should be -EIO for any iteration other than the first
> */
> >              if ( rc && i )
> >                  rc = -EIO;
> >
> > But the guest_physmap_add_entry() is problematic as it will IOMMU map
> pages
> > as well, which is probably not wanted.
> 
> Yeah, I'd prefer if we avoided establishing IOMMU mappings here.
> How about transforming set_foreign_p2m_entry() into
> set_special_p2m_entry(), with a type passed in?
> 

That sounds like it might work.

Julien, do you want page types to distinguish caller-owned resources from 
normal RAM are you ok with p2m_ram_rw even though it could be subject of 
another domain's foreign map?

  Paul

> Jan
> 


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