[libvirt] [PATCH v5] qemu: Connect to guest agent iff needed

[John Ferlan]

On 02/03/2016 08:38 AM, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1293351
> 
> Since we already have virtio channel events, we know when guest
> agent within guest has (dis-)connected. Instead of us blindly
> connecting to a socket that no one is listening to, we can just
> follow what qemu-ga does. This has a nice benefit that we don't
> need to 'guest-ping' the agent just to timeout and find out
> nobody is listening.
> 
> The way that this commit is implemented:
> - don't connect in qemuProcessLaunch directly, defer that to event
>   callback (which already follows the agent) -
>   processSerialChangedEvent
> - after migration is settled, before we resume vCPUs, ask qemu
>   whether somebody is listening on the socket and if so, connect
>   to it.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
> 
> diff to v4:
> - drop asking qemu in qemuConnectAgent; in most cases we were asking twice.
>   Rather put explicit virtio channel querying into places that were missing it
>   anyway.
> 
> - Move qemuConnectAgent in qemuProcessReconnect() *after* we have refreshed
>   channel states.
> 
>  src/qemu/qemu_migration.c | 15 +++++++++++++++
>  src/qemu/qemu_process.c   | 39 ++++++++++++++++++++++++---------------
>  src/qemu/qemu_process.h   |  2 ++
>  3 files changed, 41 insertions(+), 15 deletions(-)
> 

ACK - looks better I think now.

John