Re: [Qemu-devel] [PATCH 2/2] spice-qemu-char: register interface on post load

[Hans de Goede]

Hi,

On 03/22/2013 09:16 AM, Alon Levy wrote:
> > Ji,
>
> Ji,
>
> > On 03/21/2013 05:35 PM, Alon Levy wrote:
> > > The target has not seen the guest_connected event via
> > > spice_chr_guest_open or spice_chr_write, and so spice server
> > > wrongly
> > > assumes there is no agent active, while the client continues to
> > > send
> > > motion events only by the agent channel, which the server ignores.
> > > The
> > > net effect is that the mouse is static in the guest.
> > >
> > > By registering the interface on post load spice server will pass on
> > > the
> > > agent messages fixing the mouse behavior after migration.
> > >
> > > Note that qemu_be_is_fe_connected is called when the vm is already
> > > running, to avoid any possible order of vmstate loading issue, i.e.
> > > device loading after chardev post_load being called back.
> >
> > This seems needlessly complicated, I agree you should wait with
> > calling qemu_be_is_fe_connected till the vm is running, but why not
> > simply use qemu_add_vm_change_state_handler for that, and in the
> > handler check for state == RUN_STATE_RUNNING ?
>
> If I do that I should register it on post load and unregister it after it's done

Why, you can simply always have it there:

1) All it will do is, if transitioning to running and qemu_be_is_fe_connected 
returns
true, call vmc_register_interface, which is protected against being called 
multiple
times and if qemu_be_is_fe_connected returns true the vmc should always be 
registered.

2) The code will call qemu_be_is_fe_connected whenever the state changes to 
RUNNING,
this happens on vm-start and post-migrate, on vm-start qemu_be_is_fe_connected 
will
always return 0, so the whole thing is a nop.

Regards,

Hans