[Qemu-discuss] State of USB Pass-Through with isochronous transfers

[Bockholdt Arne]

Hi all,

I try to get an DVB-USB adapter working in a KVM-based virtual machine.
The adapter works well when connected to the host but mapped to a guest
via USB Pass Through it seems to miss frames (and interrupts ?). The
MPEG2 gets corrupted and the adapter is unusable. 

I've tested other USB devices (mass storage...) mapped to the guest and
they seem to work as expected.

The only obvious difference to the other devices is, that the DVB
adapter uses isochronous transfers for the data. 

I've tried all combinations of USB2/USB3 controller settings. 

Question: Are isochronous USB transfers supported from QEMU or are there
any (known) limitations ? 

Thank you in advance !

QEMU: 2.2
Host + Guest Kernel: 4.1.2
Arch: x86_64

USB related guest qemu config :

<controller type='usb' index='0' model='nec-xhci'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09'
function='0x0'/>
    </controller>
    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <vendor id='0x0572'/>
        <product id='0x0320'/>
      </source>
    </hostdev>


Output of lsusb -vv  in guest: 

Bus 001 Device 002: ID 0572:0320 Conexant Systems (Rockwell), Inc. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x0572 Conexant Systems (Rockwell), Inc.
  idProduct          0x0320 
  bcdDevice            0.00
  iManufacturer           1 Bestunar Inc
  iProduct                2 DVB-T2/C USB-Stick
  iSerial                 3 20140126
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           69
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          4 Default
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              500mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x01  EP 1 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       1
      bNumEndpoints           3
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x01  EP 1 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0bac  2x 940 bytes
        bInterval               1
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  bNumConfigurations      1
Device Status:     0x0000
  (Bus Powered)