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

Il 13/05/2014 11:50, Ian Campbell ha scritto:
On Tue, 2014-05-13 at 10:00 +0200, Fabio Fantoni wrote:
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

Does QXL change that answer?
QXL and other emulated vga is now not supported on pv domUs because
require an emulated pci bus and MMIO not supported on pv domUs FWIK.
Right, but what about the previous paragraph? That was the important bit
for me to understand, since it impacts the entire configuration model
and libxl API.

During my first test, I was enabled spice in pv domus but the guest wont
show nothing while connecting to it.
On my second shot, I've added -vga xenfb but it is deprecated. This way
I've got at least video out but no mouse nor keyboard.
Following the suggestions from Stefano Stabellini I've then activated
vfb the same way as for vnc and i got it all working but mouse, which is
only visible in some circumstances (such grafical debian installer) but
always working (even if not visible).
The last one is the actual patch.
Probably the vfb part is not complete or at least improvable.
Perhaps it is even not necessary if pvfb will became modified to works
with spice, so domUs use this through its modules.
Is SPICE a mechanism for exposing the PVFB or is it something entirely
separate? That is the crux of my question above.

I added also qemu-devel and spice-devel on cc:
Any one on this please?

I feel I'm not perfectly undrestanding pvfb. Please would you like
better describe me this component?
I need to understand what it is this patch is actually doing. I'm
starting to worry that perhaps you don't understand either.

Make possible using spice with basic features also on pv domUs.
Since emulated vgas is not supported on pv I use vfb instead, even if this part is incomplete and rudimental. I'm waiting from some aswers from spice and qemu teams to share some light on the question above.

Thanks for any reply and sorry for my bad english.

Another thing: i noticed that vnc has all its parameters duplicated in
vfb too. For the moment I omissed them since i feel they are not
necessary - aren't they
It really depends on the answer to my questions above.

If SPICE is nothing to do with PVFB then it obviously makes no sense for
it to be separate.

If SPICE is just a backend for PVFB then it actually makes *more* sense
to expose spice as a PVFB configuration parameter than as a set of top
level options. The fact that VNC is exposed as a top level thing too is
somewhat anomalous but was done for xend compatibility (nb: it is the
top level duplicating the vfb VNC settings, not vice versa IMHO).


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