[Bug 1884684] Re: QEMU 5.0: Guest VM hangs/freeze when unplugging USB device

[TheCatFelix]

Link to bug on the proxmox side:

https://bugzilla.proxmox.com/show_bug.cgi?id=2781

** Bug watch added: bugzilla.proxmox.com/ #2781
   https://bugzilla.proxmox.com/show_bug.cgi?id=2781

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https://bugs.launchpad.net/bugs/1884684

Title:
  QEMU 5.0: Guest VM hangs/freeze when unplugging USB device

Status in QEMU:
  New

Bug description:
  Setup:

  Host: Debian/SID, Kernel 5.6, QEMU 5.0
  Guest: Windows 10 VM with PCI and USB device passthrough.

  Problem: Guest VM suddenly hangs when pulling USB device out from the
  Host.

  Observations:
   - Issue appears to be related to QEMU 5.0
     - It started after an upgrade to QEMU 5.0.
     - Downgrading only QEMU on multiple systems fixes the issue.

   - Issue is very reproducible.
     - Most of the time within a few attempts of pulling/reconnecting the 
device.
     - Issue happens with multiple devices (I did try standard HID devices, a 
webcam and an x-ray sensor).

   - Guest just hangs.
     - Display output remains on last frame shown.
     - Ping to Guest immediately stops working.
     - Logs in the Guest stop logging immediately.

   - Host is fine and thinks the Guest is fine. 
     - Guest continues to show as running in "virsh list".
     - No suspicious entries in the QEMU logs.
     - No suspicious entries in Host syslogs/messages.
     - Host can can kill guest "virsh destroy" and respawn fine.

   - Issue seems widespread.
     - Multiple similar reports from ProxMox users after upgrade to ProxMox 6.2 
for both Windows and Linux guests (First version that uses QEMU 5.0)

  
https://forum.proxmox.com/threads/vm-freezes-when-disconnecting-usb-keyboard-and-mouse.70287/
  https://forum.proxmox.com/threads/usb-drive-crashes-vm.70214/
  
https://forum.proxmox.com/threads/latest-proxmox-usb-disconnects-freeze-kvm.70398/
  
https://forum.proxmox.com/threads/vm-with-gpu-passthrough-freezes-when-turning-off-monitor-after-proxmox-6-2-upgrade.69821/
  
https://forum.proxmox.com/threads/vm-with-gpu-passthrough-freezes-when-turning-off-monitor-after-proxmox-6-2-upgrade.69824/

  I'd be more than happy any debugs that might be helpful.

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