Updated image property did not synced to instance

[bryan]

We created an instance and then rebooted it, but the instance xml is changed after we reboot it, the following lines were added to the xml:

    <input type='keyboard' bus='usb'>
      <alias name='input1'/>
      <address type='usb' bus='0' port='2'/>
    </input>

We read the nova code, find that the input device info was refreshed into nova db using the following line: nova.virt.libvirt.driver.LibvirtDriver.spawn#self._register_undefined_instance_details(context, instance),

but when the instance is booting, nova.virt.libvirt.driver.LibvirtDriver.spawn#xml = self._get_guest_xml(context, instance, network_info, disk_info, image_meta, block_device_info=block_device_info, mdevs=mdevs, accel_info=accel_info). This line records the xml without the usb keyboard setting. When the instance is hard rebooted, nova will use the setting set by the previous line and regenerate the xml, this may be the trick.

Thank you for looking into it.