[Qemu-devel] [Bug 1426092] Re: virtio-balloon-device locks up Guest

[Thomas Huth]

Looking through old bug tickets... can you still reproduce this issue
with the latest version of QEMU? ... anyway, this rather sounds like a
bug with the guest kernel to me, so in case this problem persists, you
likely should report this in the kernel bug tracker instead.

** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1426092

Title:
  virtio-balloon-device locks up Guest

Status in QEMU:
  Incomplete

Bug description:
  Setting arbitrary balloon target values locks up the guest in some cases 
crashes it, if the target memory is < used +~5% free.  
  Found while testing aggressive memory over-commit, scenarios.
  You get messages like:

  [  155.827448] [<c002060c>] (show_stack) from [<c041c518>] 
(dump_stack+0x6c/0x88)
  [  155.837076] [<c041c518>] (dump_stack) from [<c0091994>] 
(warn_alloc_failed+0xe0/0x120)
  [  155.847075] [<c0091994>] (warn_alloc_failed) from [<c0094480>] 
(__alloc_pages_nodemask+0x600/0x91c)
  [  155.859039] [<c0094480>] (__alloc_pages_nodemask) from [<c00da414>] 
(balloon_page_enqueue+0x20/0xbc)
  [  155.870556] [<c00da414>] (balloon_page_enqueue) from [<c025d794>] 
(balloon+0x140/0x2cc)
  [  155.881377] [<c025d794>] (balloon) from [<c0043b38>] (kthread+0xd8/0xf4)

  page dumped bacause: nonzero _count
  BUG: BAad page state in process Xorg pfn:396e5

  Test Environment:
  x86_64
  Ubuntu 13.10, Guest Linux Kernel 3.19, qemu 2.2.0 with following patches 
applied - balloon OOM enhancement
  commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5
  Author: Raushaniya Maksudova <address@hidden>

  Boot guest with '-balloon virtio', -qmp .... -hmp access
  1. sudo info balloon | socat - tcp4-connect:127.0.0.1:4444
     - or over qmp interface
  {"execute":"qom-get", "arguments": { "path": 
"/machine/peripheral-anon/device[1]","property": "guest-stats" }}
  {"return": {"stats": {"stat-swap-out": 0, "stat-free-memory": 513454080, 
"stat-minor-faults": 1261, "stat-major-faults": 0, "stat-total-memory": 
526073856, "stat-swap-in": 0}, "last-update": 11109}}

  2. Take memory down check free memory using (1)
  3. Issue "sudo echo balloon XXX | socat - tcp4-connect:127.0.0.1:4444" - XXX 
is value in threshold mentioned above
     and you get Guest lockup

  ARM - samething except '-device virtio-balloon-device' used

  Libvirt - virsh setmem causes same issue.

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