Re: Strange qemu6 regression cauing disabled usb controller.

[Daniel P . Berrangé]

On Thu, Sep 30, 2021 at 03:48:44PM +0200, Remy Noel wrote:
> Hello,
> 
> I'm encountering a nagging issue with usbredir and a windows guest, but 
> although I did pinpoint the commit that caused the issue, I have a hard time 
> understanding it.
> 
> The issue occurs when a two usbredir devices are added to a guest windows vm. 
> When the second device is added, the UHCI usb controller is disabled by 
> windows with an error code 43 (can be seen with in the usb adapters section 
> of the device manager).
> 
> The commit causing the issue (everything works well when reverting it) is 
> 7bed89958bfbf40df9ca681cefbdca63abdde39d : device_core: use drain_call_rcu in 
> in qmp_device_add.

Co-incidentally we've just had another bug report filed today that
suggests 7bed89958bfbf40df9ca681cefbdca63abdde39d as a buggy commit
causing deadlock in QEMU

  https://gitlab.com/qemu-project/qemu/-/issues/650

Regards,
Daniel
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