Arch Linux

Description:
Using latest version of qemu 2.9.0 & libusb 1.0.21-2
I'm hitting a very old bug of libusb, which is descibed here:

http://www.libusb.org/ticket/70


Additional info:
qemu-system-x86_64: libusb_release_interface: -4 [NO_DEVICE]
libusb: error [_open_sysfs_attr] open /sys/bus/usb/devices/2-1/bConfigurationValue failed ret=-1 errno=2


Steps to reproduce:

* Set-up a qemu emulation with option to passthrough USB-to-Serial converter (didn't try with other hardware).
* Start your emulated system with OS
* Your passed-through device will be available in guest OS -> okay
* you may even "device_add" and "device_del" from monitor -> you device will be added or removed from guest OS

* Physically disconnect device from HOST when device is removed with "device_del" BEFOREHAND -> all is OK, you can re-add it later on.

* Physically disconnect USB device from HOST while device is still shared in guest.
* in qemu monitor -> you will get errors that i mentioned in "additional info"
* reconnection of device is not possible any more -> you will have to restart whole emulated environment.