Re: [libvirt] [PATCH v1 0/4] libxl: channels support

On 09/20/2016 05:14 AM, Michal Privoznik wrote: > On 20.09.2016 00:04, Jim Fehlig wrote: >> On 09/16/2016 05:43 PM, Joao Martins wrote: >>> Hey, >>>

>>> Additionally what does "state" >>> signify for virtio case: is it that the guest agent is connected, or that the >>> virtio serial is connected? Looking at the qemu driver on >>> processSerialChangedEvent it sounds to me like it's about the serial state. >> >> AFAICT you are right, but perhaps Michal is kind enough to confirm. I think he >> is familiar with this code. > > That attribute is put by libvirt into live XML so that mgmt apps can > query for it. The attribute says whether the guest part of channel is > opened by a process running within guest. In case of the qemu-ga whether > we have the guest agent up & running. Whenever the guest end of a > channel is opened/closed, qemu sends us an event so we can update our > internal state and put the correct value when formatting live XML. > Therefore, it makes no sense to make this attribute RW (meaning users > could set it), obviously. Hmm if it refers to qemu agent actually (dis)connected from guest side it might be difficult to provide the same "state" semantics in libxl driver at least without changes on the toolstack. If it referring to virtio-serial state we could easily do that by periodically calling libxl_channel_getinfo until state is 4 (connected). But it's the actual agent process state as connected in which case to have "state" attribute we would need to add similar to libxl event DOMAIN_CREATE_CONSOLE_AVAILABLE but instead referring to the guest channel.