Difference between revisions of "Nova/USB device&USB controller"

Revision as of 03:50, 1 March 2014

USB device and USB controller Features

Background

Currently, nova has already supported function of pci-passthrough, but dosen't support usb-passthrough. I think usb-passthrough is also a important and necessary function especially in private cloud.

User scenarios

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

2. When a user run a ERP software, him may need a usb-key provided by software provider for authentication.

3. When a user want to copy data to a removable media for business trip him may want a usb data disk.

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 pass-through usb devices
   <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 disks
     <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 maxmum of 2 while ehci controller support maxmum of 6.
  (2)If create vm without usb controller, qemu will default create a uhci controller but not support creating other type of controllers.
  (3)If create vm with usb device but no usb controller, the usb device will default be attached to the default uhci controller, but speed may mismatch.
  (4)There are two ways for supporting more usb devices. 1. Add cascaded hubs and connect usb devices to hubs. 2.Create more controllers and connect usb devices to different controllers.
  (5)When create vm with a pair of usb hub and ehci controller, the vm crashed. Error was thrown by qemu(why?)

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. Things that should be considered:

   (1)Support creating usb controller
   There already have a bp for this in https://blueprints.launchpad.net/nova/+spec/add-usb-controller, the key processes are described below:
      <1>In extra_specs of flavor add a property for usb controller: eg {'controllers':[{'type':'piix3-uhci', 'quantity': 1},{'type':'ehci', 'quantity': 2}]}  
      <2>Add function of create usb controller in libvirt driver.
          Detailed things: How to generate index field which not duplicate from other controllers)?
     
   (2)Support attach usb device when create vm
   The basic processes can refer to pci-passthrough, are described below:
     <1>System automatically discover usb devices and save them to db.
         Detailed things:
         How to distinguish usb devices from other devices like usb controllers in a host?
         A datatable usb_devices may been needed for storing usb devices information like pci_devices.
         How to uniquely identify a usb device? One choose is node id + device id(address or label or dev_id) which stored in usb_devices.
     <2>In extra_specs of flavor add a property for usb devices: eg {'devices':[{'node_id':'1', 'dev_id':'pci_0000_00_03_0', 'usbcontroller_type':'piix3-uhci'},{{'node_id':'1', 'dev_id':'pci_0000_00_03_1', 'usbcontroller_type':'ehci'}]}  
     <3>Add UsbDeviceFilter for locating the correct node.
     <4>Add algorithm in libvirt driver for choosing usb controller.
     And so on.