Attaching a USB device to KVM that reconnects frequently

August 21, 2017 - Reading time: 4 minutes

I was trying to flash a new firmware to my BT headset (Sena SMH5-FM) and found out that the device reconnects several times during the flash process. Since KVM forces the use of BUS and ID rather than VendorID:DeviceID and the ID increments by one every reconnect this never works more than one time. To work around this I made a solution using UDEV to force a connect/reconnect of the device in KVM everytime it is being connected/disconnected to/from the host.

First find out the name of your KVM machine, you can try this command to get only the name portion

ps -ef | grep kvm |sed -n -e 's/^.*\(-name \)/\1/p'| cut -f2 -d" "

Mine is called win2k12r2, albeit a Win10

Stop the VM and create the following file (if you already tried to flash and you have a device like mine that also changes the DeviceID a couple of times make more entries) -> replace Sena with a portion of the name or brand of your device (see output lsusb)

grep -B3 Sena /var/log/syslog | sed -n -e 's/^.*\(idProduct\)/\1/p' | sort | uniq

I got this as a result (I suppose they just change it twice and that the logic is xxxx becomes yxxx and one time they use a generic ffff)

idProduct=4d65
idProduct=cd65
idProduct=ffff

The VendorID is always the same and for Sena it is 092b

Next I created a USB device xml for everyone of them under

/etc/libvirt/qemu/hostdev-092b:ffff.xml

<hostdev mode='subsystem' type='usb'>
  <source>
    <vendor id='0x092b'/>
    <product id='0xffff'/>
  </source>
</hostdev>

and a UDEV rule to connect and disconnect them

/etc/udev/rules.d/10-local.rules

ACTION=="add", ATTRS{idVendor}=="092b", ATTRS{idProduct}=="ffff", RUN+="/usr/bin/virsh attach-device win2k12r2 /etc/libvirt/qemu/hostdev-092b:ffff.xml"
ACTION=="remove", ATTRS{idVendor}=="092b", ATTRS{idProduct}=="ffff", RUN+="/usr/bin/virsh detach-device win2k12r2 /etc/libvirt/qemu/hostdev-092b:ffff.xml"
ACTION=="add", ATTRS{idVendor}=="092b", ATTRS{idProduct}=="cd65", RUN+="/usr/bin/virsh attach-device win2k12r2 /etc/libvirt/qemu/hostdev-092b:cd65.xml"
ACTION=="remove", ATTRS{idVendor}=="092b", ATTRS{idProduct}=="cd65", RUN+="/usr/bin/virsh detach-device win2k12r2 /etc/libvirt/qemu/hostdev-092b:cd65.xml"
ACTION=="add", ATTRS{idVendor}=="092b", ATTRS{idProduct}=="4d65", RUN+="/usr/bin/virsh attach-device win2k12r2 /etc/libvirt/qemu/hostdev-092b:4d65.xml"
ACTION=="remove", ATTRS{idVendor}=="092b", ATTRS{idProduct}=="4d65", RUN+="/usr/bin/virsh detach-device win2k12r2 /etc/libvirt/qemu/hostdev-092b:4d65.xml"

After this you can start your VM and try to flash your device, if it still fails check again to see if there are no extra DeviceID's in the syslog