Re: [Xen-devel] [PATCH v7 01/12] x86/mm: allow a privileged PV domain to map guest mfns

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 25 September 2017 16:31
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] [PATCH v7 01/12] x86/mm: allow a privileged PV
> domain to map guest mfns
> 
> >>> On 25.09.17 at 16:56, <Paul.Durrant@xxxxxxxxxx> wrote:
> >>  -----Original Message-----
> >> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of
> Jan
> >> Beulich
> >> Sent: 25 September 2017 15:50
> >> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> >> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; xen-
> >> devel@xxxxxxxxxxxxxxxxxxxx
> >> Subject: Re: [Xen-devel] [PATCH v7 01/12] x86/mm: allow a privileged PV
> >> domain to map guest mfns
> >>
> >> >>> On 25.09.17 at 16:42, <Paul.Durrant@xxxxxxxxxx> wrote:
> >> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> >> Sent: 25 September 2017 14:03
> >> >> >>> On 18.09.17 at 17:31, <paul.durrant@xxxxxxxxxx> wrote:
> >> >> The other aspect I don't understand is why this is needed for PV
> >> >> Dom0, but not for PVH. The answer here can't be "because PVH
> >> >> Dom0 isn't supported yet", because it eventually will be, and then
> >> >> there will still be the problem of PVH supposedly having no notion
> >> >> of MFNs (be their own or foreign guest ones). The answer also
> >> >> can't be "since it would use XENMAPSPACE_gmfn_foreign", as
> >> >> that's acting in terms of GFN too.
> >> >
> >> > The hypercall is PV-only. For a PVH/HVM tools domain things are
> handled
> >> by
> >> > doing an add-to-physmap to gfns specified by the tools domain. I have
> >> tested
> >> > both PV and HVM clients of my new memory op.
> >>
> >> And how is this add-to-physmap any better superpage shattering
> >> wise than the old mechansim?
> >
> > Because the calling domain can make an intelligent choice about what gfns
> to
> > use?
> 
> And why was an intelligent choice not possible with the old
> mechanism? The calling domain is the tool stack one in both
> cases, isn't it?

True, I suppose.

  Paul

> 
> Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel