[Qemu-devel] USB pass through via usb-host

[Qemu-devel] USB pass through via usb-host

[Alexey Kardashevskiy]

Hi!

I am trying usb-host with the root hub like this:

-device nec-usb-xhci,id=id3 \
-device usb-host,id=id4,hostbus=1,hostaddr=1

In the guest I see emulated XHCI and 2 root hubs (and I see exactly the 
same picture if I do not pass anytning via usb-host):

[root@localhost ~]# lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
[root@localhost ~]# lspci
00:00.0 USB controller: NEC Corporation uPD720200 USB 3.0 Host Controller 
(rev 03)


The questions are:
1. can we really pass a root hub to a guest? What is expected to happen 
there? Should not I see 3 root hubs (2 from emulated XHCI and 3rd one from 
usb-host)?

2. can we tell if the root hubs in the guest are emulated or from usb-host?


The questions are to understand what is supported/expected and what is not 
rather than report a bug or something :)

Thanks!


This is my host:

aik@fstn1:~$ lspci -s 0003:09:00.0
0003:09:00.0 USB controller: Texas Instruments TUSB73x0 SuperSpeed USB 3.0 
xHCI Host Controller (rev 02)
aik@fstn1:~$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 007: ID 046b:ff10 American Megatrends, Inc. Virtual Keyboard 
and Mouse
Bus 001 Device 009: ID 046b:ff31 American Megatrends, Inc.
Bus 001 Device 003: ID 046b:ff01 American Megatrends, Inc.
Bus 001 Device 011: ID 0fe6:8101 Kontron (Industrial Computer Source / ICS 
Advent) DM9601 Fast Ethernet Adapter
Bus 001 Device 012: ID 136b:0001 STEC
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


-- 
Alexey

Re: [Qemu-devel] USB pass through via usb-host

[Gerd Hoffmann]

> The questions are:
> 1. can we really pass a root hub to a guest?

No.  You can't pass-through hubs (no matter whenever root or other).

> What is expected to happen 
> there?

Nothing.  Hubs are ignored by usb-host.

> 2. can we tell if the root hubs in the guest are emulated or from usb-host?

They are emulated.

cheers,
  Gerd