On 11/18/21 07:37, Han Han wrote:

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?

Detaching a device requires the guest cooperation, while in contrast the device attach does not. So I'm guessing that your guest isn't in a state where it can satisfy the detach request. The DEVICE_REMOVED event is emitted whenever DEVICE_DELETED event appears on the monitor (may be delayed for a couple of microseconds, because libvirt needs to update its internal state first). Hope this helps. Michal