Re: [libvirt] qemu: domain notification for serial channel changes

On Mon, Nov 07, 2016 at 13:31:30 +0000, Daniel Berrange wrote: > On Mon, Nov 07, 2016 at 08:22:59AM -0500, Matt Broadstone wrote: > > Hi, > > > > I was in the process of implementing a custom qemu agent which > > communicates over virtio-serial channels, when I noticed that the only > > way to receive channel state change notifications was to poll the > > domstatus XML file. There does seem to be code in libvirt to monitor > > for serial change events > > (https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_driver.c;h=...), > > however it's hardcoded/specific to the qemu-ga (explicitly checking > > for ports named "org.qemu.guest_agent.0"). > > > > It occurs to me that while there was a class of events added for guest > > lifecycle changes, it might be a more generic solution to provide > > events for character device changes. Am I missing some existing > > functionality here? I'm a first-time poster here so I was hoping to > > both signal my intent to implement something more generic, as well as > > ping the community to see if there would be interest in this work or > > reasons why I shouldn't be doing this. > > Yes, having that previous event tied to just the QEMU guest agent looks > like a mistake to me. We should have a general lifecycle evnt for > channel devices. It would basically be the same as the guest agent > lifecycle event, but would include the port name, so you can distinguish > events from different channels. That choice was deliberate. I planned to add a separate event for channels but never got around to do it actually. The guest agent event is separate since libvirt can have different handling regarding the guest agent state and I did not want to mix them. Peter