Questions on device-added and device-removed events

[Han Han <hhan@xxxxxxxxxx>]

Hi developers,

When the guest OS is booting, the event for live attachment could be caught by libvirt, while the event for live detachment could not.

Version:

libvirt-7.9

qemu-kvm-6.1

Steps:

Terminal 1:
➜  ~ virsh event --loop --all

Terminal 2:

➜  ~ virsh start avocado-vt-vm1; qemu-img create /tmp/vdb 10M; virsh attach-disk avocado-vt-vm1 /tmp/vdb vdb; virsh detach-disk avocado-vt-vm1 vdb

The outputs from terminal 1:

event 'agent-lifecycle' for domain 'avocado-vt-vm1': state: 'disconnected' reason: 'domain started'      
event 'lifecycle' for domain 'avocado-vt-vm1': Resumed Unpaused
event 'lifecycle' for domain 'avocado-vt-vm1': Started Booted
event 'device-added' for domain 'avocado-vt-vm1': virtio-disk1
event 'agent-lifecycle' for domain 'avocado-vt-vm1': state: 'connected' reason: 'channel event'

As you can see, the device live attachment and the device detachment are both executed when the guest OS is booting, but there is only the event 'device-added' is recorded.

So my questions are:

1. Is it the expected results for the results above?

2. If so, what is the internal difference between 'device-added' and 'device-removed'?

3. I notice there is the DEVICE_DELETED event in qmp? Any relation between the 'device-removed' of libvirt and the DEVICE_DELETED of qmp?