Re: [Xen-devel] [RFC PATCH 4/6] vm_event: Use slotted channels for sync requests.

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Petre Ovidiu PIRCALABU [mailto:ppircalabu@xxxxxxxxxxxxxxx]
> Sent: 08 January 2019 16:14
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu
> <wei.liu2@xxxxxxxxxx>; Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>; Konrad
> Rzeszutek Wilk <konrad.wilk@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>; Tamas K Lengyel <tamas@xxxxxxxxxxxxx>; Jan
> Beulich <jbeulich@xxxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>
> Subject: Re: [Xen-devel] [RFC PATCH 4/6] vm_event: Use slotted channels
> for sync requests.
> 
> On Tue, 2019-01-08 at 15:08 +0000, Paul Durrant wrote:
> > >
> > >
> > > Also, for the current vm_event implementation, other than using the
> > > hvm_params to specify the ring page gfn, I couldn't see any reason
> > > why
> > > it should be limited to HVM guests only. Is it feasible to assume
> > > the
> > > vm_event mechanism will not ever be extended to PV guests?
> > >
> >
> > Unless you limit things to HVM (and PVH) guests then I guess you'll
> > run into the same page ownership problems that ioreq server ran into
> > (due to a PV guest being allowed to map any page assigned to it...
> > including those that may be 'resources' it should not be able to see
> > directly). Any particular reason why you'd definitely want to support
> > pure PV guests?
> >
> >   Paul
> 
> No, but at this point I just want to make sure I'm not limiting the
> vm_events usage.

Ok, but given that a framework (i.e. ioreq) exists for HVM/PVH guests then IMO 
it makes sense to target those guests first and then figure out how to make 
things work for PV later if need be.

  Paul

> 
> Many thanks,
> Petre

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