Nova/USB device&USB controller

USB device and USB controller Features

Background

Currently, nova has already supported pci-passthrough, but still dosen't support usb-passthrough. In fact usb device is a kind of necessary device in some user scenarios in private cloud.

User scenarios

1. When i transfer money online, i need a usb-key provided by bank for authentication.

2. When i start a erp software, i need a usb-key provided by software provider for authentication.

3. I need a usb data disk for transferring business data.

Technical verification

1. Test case

   Attach different number of usb devices to different type of usb controllers.

2. Xml definition

  (1)Sample of usb controller:
   <controller type='usb' index='2' model='piix3-uhci'/>
   <controller type='usb' index='1' model='ehci'/>

  (2)Sample of host usb device pass-through
   <hostdev mode='subsystem' type='usb'>
    < source>
     <vendor id='0x136b'/>
     <product id='0x0003'/>
     <address bus='2' device='2'/>
    </source>
    <address type='usb' bus='1' port='1'/>
   </hostdev>

  (3)Sample of emulated usb disk
     <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      < source file='/home/vms/usb/sdb.qcow2'/>
      <target dev='sdb' bus='usb'/>
      <address type='usb' bus='1' port='1'/>
    </disk>

3. The test results

  (1)Usb controllers have a maximum port restriction. Uhci controller support 2 port while ehci controller support  6 port.
  (2)If create vm without usb controller, the qemu will default create a usb 1.1 controller but not other type's controllers.
  (3)If create vm with usb device but not usb controller, the usb device will default attach to uhci controller, but the speed may mismatch.
  (4)There are two ways to support for more usb devices. 1. Add cascaded hubs. 2.Create more controllers.
  (5)When create vm with a pair of usb hub and ehci controller, the vm crashed.

Proposed solution

1. use cases

   Case 1:
   (1)Admin/User create a flavor with usb controllers(key parameters: type, quantity). 
   (2)Admin/User create a vm with flavor above, the system create controllers with specified type and quantiy.
   
   Case 2:
   (1)Admin/User create a flavor with usb devices(key parameters: identifiers that can find the device, like in which host, bus number and device number and so on).
   (2)Admin/User create a vm with flavor above, the system check if usb devices are in the same host and available, then create vm in the host with usb devices attached to default uhci controller. 

   Case 3:    
   (1)Admin/User create a flavor with usb controllers(key parameters: type, quantity) and usb devices(key parameters: identifiers and usb controller type).
   (2)Admin/User create a vm with flavor above, the system check if usb devices are in the same host, available and matching usb controllers,  then create controllers and attach usb devices to matched controllers.  

2. Key processes