RE: [Qemu-devel] USB storage cannot be recognized on guest Linux domain?

[Yu, Xiaoyang]

Hi Lonnie,

Thanks a lot for the information.

In our use case, we do not know the USB disk information before it is plugged 
by customer, so we cannot start qemu with -usbdevice.

For Linux, reload the uhci_hcd driver works. If we use this solution in our use 
case, then we need to issue an interrupt (maybe by pic_set_irq_new?) to the 
guest OS when QEMU detect a USB device is attached, and then the guest OS will 
reload the uhci_hcd driver. Is that right? Currently there is something wrong 
with the list archive server, so I haven't search out any example code from it 
:-(

I found that there is a patch to add the UHCI suspend/resume support in the 
archive posted by you, but it cannot be applied to QEMU-DM 0.8.2 directly:
http://lists.gnu.org/archive/html/qemu-devel/2006-04/msg00576.html

I wonder why there is no official UHCI suspend/resume support in QEMU. To 
reload the uhci_hcd driver seems to be only a work around. Sometimes it even 
cause kernel oops. 

I also wonder why the kernel 2.6.11-1.1369_FC4 can recognize USB storage 
without UHCI suspend/resume support.

Thanks
Xiaoyang
 
-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Lonnie Mendez
Sent: 2007年2月15日 10:44
To: address@hidden
Subject: RE: [Qemu-devel] USB storage cannot be recognized onguest Linuxdomain?

On Thu, 2007-02-15 at 10:36 +0800, Yu, Xiaoyang wrote:
> Thanks a lot for the instruction. Will the suspend/resume support be added in 
> the future release? 
> 
> Without the suspend/resume support, is there anything can be done in the 
> guest domain to help detect a USB device? Maybe patch the kernel?

For windows you can disable the power management for the controller.
That will cause windows to constantly poll hub status.

For linux you have to reload the uhci hcd driver.  Notice that starting
qemu with -usbdevice works.  The code to implement this is very easy.
You basically set/clear some bits and trigger an interrupt.  See list
archives for example code.