Thanks Thomas for Your suggestion. Unfortunately I cannot achieve the reconnection:
KVM runs with following parameters: -usb -device usb-host,vendorid=0x04e8,productid=0x3242,id=drucker -monitor unix:qemu-monitor-socket,server,nowait With the Unix socket, I can now pipe commands to the qemu monitor. This info command works: echo 'info status' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) info status VM status: running What I have is this: - disconnect USB printer (Product Samsung ML-1510_700) - stop KVM - connect USB printer - start KVM echo 'info usb' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) info usb Device 0.1, Port 1, Speed 12 Mb/s, Product QEMU USB Tablet Device 0.2, Port 2, Speed 12 Mb/s, Product QEMU USB Hub Device 0.3, Port 2.1, Speed 12 Mb/s, Product Samsung ML-1510_700, ID: drucker Printer works. - disconnect printer echo 'info usb' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) info usb Device 0.2, Port 1, Speed 12 Mb/s, Product QEMU USB Tablet Device 0.3, Port 2, Speed 12 Mb/s, Product QEMU USB Hub Device 0.4, Port 2.1, Speed 12 Mb/s, Product Samsung ML-1510_700, ID: drucker USB Info still shows the printer, allthough it is disconnected. Remove device from KVM: echo 'device_del drucker' | socat - unix-connect:/qemu-monitor-socket Printer is removed from the device list: info usbdrucker' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) info usb Device 0.2, Port 1, Speed 12 Mb/s, Product QEMU USB Tablet Device 0.3, Port 2, Speed 12 Mb/s, Product QEMU USB Hub -connect printer printer is not shown: echo 'info usb' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) info usb Device 0.2, Port 1, Speed 12 Mb/s, Product QEMU USB Tablet Device 0.3, Port 2, Speed 12 Mb/s, Product QEMU USB Hub Add printer device: echo 'device_add usb-host,vendorid=0x04e8,productid=0x3242,id=drucker ' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) device_add usb-host,vendorid=0x04e8,productid=0x3242,id=drucker echo 'info usb' | socat - unix-connect:/qemu-monitor-socket QEMU 4.2.0 monitor - type 'help' for more information (qemu) info usb Device 0.2, Port 1, Speed 12 Mb/s, Product QEMU USB Tablet Device 0.3, Port 2, Speed 12 Mb/s, Product QEMU USB Hub Device 0.0, Port 2.2, Speed 1.5 Mb/s, Product USB Host Device, ID: drucker Device is shown, but not like when KVM is started with connected printer: Speed only 1.5 Mb/s, no vendor and product info. Printer does _not_ work. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1377095 Title: KVM guest VM does not reattach a throughpassed USB printer from Host after switching printer off and on Status in QEMU: New Bug description: Host OS: Gentoo, all packages built 2014-10-01 qemu version 2.1.0-r1 Linux kernel 3.14.14 x86_64 Intel(R) Core(TM) i3-3220T CPU @ 2.80GHz GenuineIntel GNU/Linux Guest VM: Debian 7 (Wheezy) Linux 3.2.0 686 Start command: /usr/bin/qemu-system-i386 -enable-kvm -name wheezy -k de -serial null -parallel null -hda /var/kvm/wheezy.kvm-img -daemonize -net nic,macaddr=02:00:00:00:01:31 -net tap,ifname=tap3,script=no,downscript=no -m 512 -pidfile /var/run/kvm/wheezy.pid -usb -usbdevice tablet -runas myuser -vnc 127.0.0.1:3 -usbdevice host:04e8:3242 Problem: USB printer pass-through from KVM host to guest vm only works if I start the qemu kvm when the USB printer (vendor/product ID 04e8:3242) is switched on and therefore shown in lsusb on the host. Then it is available in the started VM. But when I switch the usb printer attached to the host off, it disappears in lsusb both on the host and the VM (as expected) but when I switch the USB printer on again, it is shown on the host and also on the QEMU Monitor (Crtl Alt Shift 2 -> info usbhost), but in the VM lsusb does not show it again- so USB pass-through / hot plugging does not work. It worked with a previous Version of qemu (1.0 or something). That is very annoying, because every time I want to print something, I need to shutdown the VM, start the printer, and then start the VM (which runs cups as printer server). But after printing, I do not want the printer to keep running, so I switch it off. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1377095/+subscriptions
