I have a Windows 8.1 VM that I am passing a USB mouse, keyboard, and printer through to the VM. I am seeing udev hot-plug events in the VM log. I am wondering if these hot-plug events aren't coming from unassigned devices. If they are, maybe they should be filtered out and not "hot-plugged" if they are being passed to a VM.
2015-06-13 20:29:15.483+0000: starting up libvirt version: 1.2.15, qemu version: 2.3.0
Domain id=2 is tainted: high-privileges
Domain id=2 is tainted: host-cpu
char device redirected to /dev/pts/0 (label charserial0)
qemu: terminating on signal 15 from pid 5991
2015-06-13 20:30:01.977+0000: shutting down
2015-06-13 20:30:35.537+0000: starting up libvirt version: 1.2.15, qemu version: 2.3.0
Domain id=4 is tainted: high-privileges
Domain id=4 is tainted: host-cpu
char device redirected to /dev/pts/0 (label charserial0)
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change
libusb: error [udev_hotplug_event] ignoring udev action change