Re: [libvirt] Auto-assignment of USB devices and auto-creation of USB hubs
On Mi, 2013-09-18 at 07:33 -0400, Jamie Bainbridge wrote:
Hello,
I've been helping a customer out this week with assigning specific devices to
specific USB controllers inside his KVM VMs. He's got USB1 devices which need a UHCI
controller (because of rubbishy Windows device drivers) and USB2 devices which need a EHCI
controller ("speed mismatch" on a UHCI hub).
I've suggested config similar to this:
<controller type='usb' index='0' model='ehci'>
</controller>
<controller type='usb' index='1' model='piix3-uhci'>
</controller>
You can also do this:
<controller type='usb' index='0' model='ich9-ehci1'>
<address type='pci' domain='0x0000' bus='0x00'
slot='0x1d'
function='0x7' multifunction='on'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci1'>
<master startport='0'/>
<address type='pci' domain='0x0000' bus='0x00'
slot='0x1d'
function='0x0' multifunction='on'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci2'>
<master startport='2'/>
<address type='pci' domain='0x0000' bus='0x00'
slot='0x1d'
function='0x1' multifunction='on'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci3'>
<master startport='4'/>
<address type='pci' domain='0x0000' bus='0x00'
slot='0x1d'
function='0x2' multifunction='on'/>
</controller>
Gives you a ehci controller with uhci companions. It's a single usb
bus, with 6 ports, supporting both usb1 and usb2. Makes device
attachment a bit easier as you don't have to worry about the device
speed then.
<input type='tablet' bus='usb'/>
You can also do this here:
<input type='tablet' bus='usb'>
<address type='usb' bus='0' port='2.8'/>
</input>
<hub type='usb'>
<address type='usb' bus='1' port='2'/>
</hub>
The qemu hub supports usb1.1 only, so any usb 2.0 devices must be
plugged into a ehci root port. The hub has 8 downstream ports btw.
My observation is that you can either:
a) let libvirt plug everything into the UHCI controller, regardless of what other
controllers are there and what order they appear in
or
b) find out how many ports a controller/hub has through trial and error, manually create
USB hubs, and map every single device and port out manually
with no middle ground in between.
Correct. And if you hotplug usb devices you have to do (b) to make sure
live migration works.
<address type='usb' bus='1'/>
then save the XML, and "virsh edit" again, and all the
port/hub stuff would already be there pre-made as required.
Any thoughts? Is this worth logging an RFE for?
Sure. It's done for PCI, for good reasons.
IMO libvirt should likewise create usb addresses.
cheers,
Gerd