[PVE-User] USB Devices hotplug

Dominik Csapak d.csapak at proxmox.com
Mon Aug 14 09:31:58 CEST 2017

On 08/11/2017 03:31 PM, Gilberto Nunes wrote:
> Ok!
> I performe a fresh installation and just realize that with Virtio SCSI
> Single, command qm set doesn't work.
> I change to Virtio SCSI and qm set works properly.
> But USB Device passthrough doesn't work, unless I turn off the VM. It's not
> suppose to work on line??? I meant hotplug???
> Thanks any way


i just want to chime in here, to clarify a few things:

the 'Usb hotplug' option in the gui is sadly a bit mislabled, as
currently it only controls the hotplug of the 'use tablet as pointer 
device' option, not usb in general

with usb hotplug we currently have a few problems namely:

when adding many usb devices, it can happen that qemu
adds a usb-hub without id, which we then can never remove (because it 
has no id) so no more live migration of this vm, even if you remove all 
usb devices again

when adding the first usb2 device, we hotplug an usb2 controller,
but last time i checked, this could not be hot-unplugged, so
we are again in a situation where we cannot live migrate,
even when removing all usb devices

there are some ideas how to work around those issues, but
we have to be careful to not break old->new live migration completetly

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