[Qemu-devel] [Bug 1626596] [NEW] Lockup with vhost network

[rm]

Public bug reported:

After using Qemu in this configuration successfully for quite a while, I 
changed two things:
- moved the VM from a 8-core 4GHz host to a slower 2-core 1.6 Ghz machine
- upgraded qemu from 2.1 to 2.5

and almost immediately (in a couple hours) got hit with a vhost-related
lockup.

QEMU command line is:

qemu-system-x86_64 -enable-kvm -daemonize -monitor
unix:./monitor,server,nowait -cpu host -M q35 -balloon virtio -device
virtio-scsi-pci,id=scsi -device scsi-hd,drive=hd -drive
if=none,id=hd,cache=writeback,aio=native,format=raw,file=xxxx.img,discard=unmap
,detect-zeroes=unmap -device virtio-net-pci,netdev=net0,mac=xxxx -netdev
tap,vhost=on,id=net0,script=xxxx.sh -usbdevice tablet -smp 2 -m 512 -vnc
xxxx:yz

VM was running fine, except no network traffic was passed from/to it.
Shutting down the VM, it hung at "Will now halt." The QEMU process was
unkillable, so the only choice was to sysrq-b the entire box.

dmesg with sysrq-w attached.

** Affects: qemu
     Importance: Undecided
         Status: New

** Attachment added: "dmesg with sysrq-w"
   https://bugs.launchpad.net/bugs/1626596/+attachment/4746283/+files/vhost.txt

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https://bugs.launchpad.net/bugs/1626596

Title:
  Lockup with vhost network

Status in QEMU:
  New

Bug description:
  After using Qemu in this configuration successfully for quite a while, I 
changed two things:
  - moved the VM from a 8-core 4GHz host to a slower 2-core 1.6 Ghz machine
  - upgraded qemu from 2.1 to 2.5

  and almost immediately (in a couple hours) got hit with a vhost-
  related lockup.

  QEMU command line is:

  qemu-system-x86_64 -enable-kvm -daemonize -monitor
  unix:./monitor,server,nowait -cpu host -M q35 -balloon virtio -device
  virtio-scsi-pci,id=scsi -device scsi-hd,drive=hd -drive
  
if=none,id=hd,cache=writeback,aio=native,format=raw,file=xxxx.img,discard=unmap
  ,detect-zeroes=unmap -device virtio-net-pci,netdev=net0,mac=xxxx
  -netdev tap,vhost=on,id=net0,script=xxxx.sh -usbdevice tablet -smp 2
  -m 512 -vnc xxxx:yz

  VM was running fine, except no network traffic was passed from/to it.
  Shutting down the VM, it hung at "Will now halt." The QEMU process was
  unkillable, so the only choice was to sysrq-b the entire box.

  dmesg with sysrq-w attached.

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