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

[Hans de Goede <hdegoede@redhat.com>]

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