Re: [Qemu-devel] RFC adding ioctl's to virtserial/virtconsole

[Gerd Hoffmann]

On 08/03/10 19:53, Anthony Liguori wrote:
> On 08/03/2010 12:02 PM, Gerd Hoffmann wrote:
> > On 08/03/10 18:45, Anthony Liguori wrote:
> > > On 08/03/2010 11:42 AM, Gerd Hoffmann wrote:
> > > > spice-vmc code registers/unregisters the interface within the spice
> > > > server. So the interface is only activated in case the guest uses it.
> > > > Spice client sees the interface being active or not and can act
> > > > accordingly.
> > >
> > > So we have to migrate connected state?
> >
> > virtio-serial handles that already.
>
> And we have to propagate this upon load to the char device backend.

Happens too, by calling port->guest_open() if needed in loadvm_post().

> Do we assume that the chardev is in the CONNECTED state initially? If we
> do a loadvm at run time while we're in the CONNECTED state, do we
> generate a DISCONNECTED followed by CONNECTED state transition? If we
> loadvm to a state where we were in the DISCONNECTED state, does that
> generate DISCONNECTED followed by CONNECTED followed by DISCONNECTED or
> just DISCONNECTED?
>
> This is exactly the type of problem that we've had in the past by not
> having an API that clearly forces management of life cycle.

That indeed must be cleanly defined and for best results also enforced 
in some way, say using asserts().  That needs some bigger planning and 
not some ad-hoc "Oh lets us quickly add this" patching though.  When 
re-designing chardevs I wanna do it once and wanna do it right.

Are there BoF slots @ kvm forum?  I can try to put together something 
(current pain points + feature wishlist + better chardev data structures 
+ better chardev api) to kick a discussion either in Boston or at 
qemu-devel.  Will take some time though.

cheers,
  Gerd