Re: [Xen-devel] [PATCH v17 06/11] x86/hvm/ioreq: add a new mappable resource type...

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 03 January 2018 17:05
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: JulienGrall <julien.grall@xxxxxxx>; Andrew Cooper
> <Andrew.Cooper3@xxxxxxxxxx>; George Dunlap
> <George.Dunlap@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; Wei Liu
> <wei.liu2@xxxxxxxxxx>; StefanoStabellini <sstabellini@xxxxxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; Tim (Xen.org) <tim@xxxxxxx>
> Subject: RE: [Xen-devel] [PATCH v17 06/11] x86/hvm/ioreq: add a new
> mappable resource type...
> 
> >>> On 03.01.18 at 17:48, <Paul.Durrant@xxxxxxxxxx> wrote:
> >>  -----Original Message-----
> >> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On
> Behalf
> >> Of Jan Beulich
> >> >>> On 03.01.18 at 17:06, <Paul.Durrant@xxxxxxxxxx> wrote:
> >> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> >> Sent: 03 January 2018 15:48
> >> >> >>> On 03.01.18 at 13:19, <paul.durrant@xxxxxxxxxx> wrote:
> >> >> What is additionally confusing me is the page ownership: Wasn't
> >> >> the (original) intention to make the pages owned by the emulator
> >> >> domain rather than the guest? I seem to recall you referring to
> >> >> restrictions in do_mmu_update(), but a domain should always be
> >> >> able to map pages it owns, shouldn't it?
> >> >
> >> > I'm sure we had this discussion before. I am trying to make resource
> >> mapping
> >> > as uniform as possible so, like the grant table pages, the ioreq server
> pages
> >> > are assigned to the target domain. Otherwise the domain trying to map
> >> > resources has know which actual domain they are assigned to, rather
> than
> >> the
> >> > domain they relate to... which is pretty ugly.
> >>
> >> Didn't I suggest a slight change to the interface to actually make
> >> this not as ugly?
> >
> > Yes, you did but I didn't really want to go that way unless I absolutely had
> > to. If you'd really prefer things that way then I'll re-work the hypercall 
> > to
> > allow the domain owning the resource pages to be passed back. Maybe it
> will
> > ultimately end up neater.
> 
> A 3rd opinion wouldn't hurt before you invest much time.
> 

Andrew,

  Do you have any particular preferences on whether ioreq server pages are 
assigned to the tools domain or the target domain (the former requiring a tweak 
to the hypercall to pass back the owner of the resource pages)?

  Paul

> Jan


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