Re: [Qemu-devel] USB continuous reset / unplug cleanup not done properly

[Erik Rull]

Hi Gerd,

Gerd Hoffmann wrote:
>    Hi,
>
> > 1) Devices get resetted again and again on the host side and do not work
> > properly on the guest side - they work fine on the host side outside qemu.
>
> I see those too.  Not clear what is going on here.  usbfs requests seem
> to get stuck now and then for not-yet known reasons.  Sometimes they
> finish after a few seconds.  Sometimes they get stuck long enougth that
> some timeout within the guest fires and the guest resets the device.

Is it possible to increase either the timeout periods or "block" the USB 
device during it is in use by the guest, so that usbfs does not want to 
reset it?

> I see those with a F16 guest which polls the usb stick with
> test-unit-ready requests.  Letting it run idle produces a ...
>
>     usb 1-6: reset high speed USB device number 3 using ehci_hcd
>
> ... log line line in the guest now and then.  Tried to write a small
> reproducer (tool constantly sending test-unit-ready via usbfs), but that
> one works just fine without any hangs.

Is it possible to trace the USB requests at this level? Maybe there is a 
possibility to figure out why the reset happens.

> cheers,
>    Gerd

Any idea about the second point regarding the remaining devices in the info 
usb list?

Best regards,

Erik