[Spice-devel] [PATCH] migration: Don't assert() if MIGRATE_DATA comes before attaching the agent

[Uri Lublin]

On 05/15/2014 05:14 PM, Christophe Fergeau wrote:
> Hi,
>
> On Wed, Apr 30, 2014 at 08:11:38PM +0300, Uri Lublin wrote:
>
> On 04/01/2014 04:58 PM, Christophe Fergeau wrote:
>>> During seamless migration, after switching host, if a client was connected
>>> during the migration, it will have data to send back to the new
>>> qemu/spice-server instance. This is handled through MIGRATE_DATA messages.
>>> SPICE char devices use such MIGRATE_DATA messages to restore their state.
>>>
>>> However, the MIGRATE_DATA message can arrive any time after the new qemu
>>> instance has started, this can happen before or after the SPICE char
>>> devices have been created. In order to handle this, if the migrate data
>>> arrives early, it's stored in reds->agent_state.mig_data, and
>>> attach_to_red_agent() will restore the agent state as appropriate.
>> Adding more information -- I think the race here is between qemu-kvm
>> migrating the virtio-device state (with main/migration thread) vs spice
>> migrating
>> "agent" channel state.
> What do you call 'spice migrating "agent"" channel state" ? Is it the
> "MIGRATE DATA" spice message I I mention or something else?

Yes, it is the spice channel state being transferred with the 
MIGRATE_DATA message.