Re: [Xen-devel] [PATCH v4] libxl: add basic spice support for pv domUs

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-05-09 at 15:48 +0200, Fabio Fantoni wrote:

> >
> >> +    libxl_defbool_setdefault(&b_info->u.hvm.spice.enable, false);
> >> +    if (libxl_defbool_val(b_info->u.hvm.spice.enable)) {
> > I think this will cause hvm.spice to take precedence over the top-level
> > spice field, which I don't think is what you wanted, was it?
> >
> > I think you need:
> >      libxl_defbool_setdefault(&b_info->u.hvm.spice.enable, false);
> >      libxl_defbool_setdefault(&b_info->spice.enable, false);
> >      if (!libxl_defbool_val(&b_info->spice.enable) &&
> >          libxl_defbool_setdefault(&b_info->u.hvm.spice.enable))
> >              b_info->spice = b_info->u.hvm.spice;
> >
> > Then this bit:
> >
> >> +    if (libxl_defbool_val(b_info->spice.enable)) {
> >> +        libxl_defbool_setdefault(&b_info->spice.disable_ticketing, false);
> >> +        libxl_defbool_setdefault(&b_info->spice.agent_mouse, true);
> > Does this work for PV guests? Having the default vary with b_info->type
> > would be fine IMHO.
> >
> > I don't see you changing the result of calling libxl__need_xenpv_qemu
> > anywhere to be true if spice is enabled. I think this means qemu won't
> > be launched unless there happens to also be a qdisk or some other qemu
> > backend.
> 
> Spice requires qemu.

Understood.

> What would I do to always start qemu with spice enabled? (even if unused 
> qdisk and vnc and/or using api instead of xl)

You need to update libxl__need_xenpv_qemu to return true if spice is
enabled, along with all the other conditions.

But: Does spice already require a VFB? In which case the existing
handing of that will suffice.

I think I'm probably confused about something: Does this patch
enable/expose SPICE to the guest? Or does it simply enable the existing
PVFB's output to be exposed from the qemu process to a spice client? I
had been thinking this was a parallel feature to PVFB, but I'm starting
to suspect this might actually be an additional feature *of* PVFB, which
is correct? (I'm afraid that depending on which it is I might have to
check back over my review to make sure I haven't suggested anything
stupid)

Does QXL change that answer?

> > Does spice not support multiple interfaces like the vfb option does? If
> > so we should plan for that in the interface I think.
> 
> I not know for sure what spice multiple interfaces support is.

I think the importance of this depends on my question about VFB.

Ian.


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