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
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