Public bug reported:

When installing qemu-kvm on a VM, KSM is enabled.

I have encountered this problem in trusty:$ lsb_release -a
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.1 LTS
Release:        14.04
Codename:       trusty
$ uname -a
Linux juju-gema-machine-2 3.13.0-40-generic #69-Ubuntu SMP Thu Nov 13 17:53:56 
UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

The way to see the behaviour:
1) $ more /sys/kernel/mm/ksm/run
0
2) $ sudo apt-get install qemu-kvm
3) $ more /sys/kernel/mm/ksm/run
1

To see the soft lockups, deploy a cloud on a virtualised env like ctsstack, run 
tempest on it, the compute nodes of the virtualised deployment will eventually 
stop responding with (run tempest 2 times at least):
 24096.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
[24124.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
[24152.072002] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24180.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24208.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24236.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24264.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]

I am not sure whether the problem is that we are enabling KSM on a VM or
the problem is that nested KSM is not behaving properly. Either way I
can easily reproduce, please contact me if you need further details.

** Affects: qemu-kvm (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: cts

** Tags added: cts

** Description changed:

  When installing qemu-kvm on a VM, KSM is enabled.
  
  I have encountered this problem in trusty:$ lsb_release -a
  Distributor ID: Ubuntu
  Description:    Ubuntu 14.04.1 LTS
  Release:        14.04
  Codename:       trusty
  $ uname -a
  Linux juju-gema-machine-2 3.13.0-40-generic #69-Ubuntu SMP Thu Nov 13 
17:53:56 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
  
  The way to see the behaviour:
  1) $ more /sys/kernel/mm/ksm/run
  0
  2) $ sudo apt-get install qemu-kvm
  3) $ more /sys/kernel/mm/ksm/run
  1
  
- To see the soft lockups, deploy a cloud on a virtualised env like ctsstack, 
run tempest on it, the compute nodes of the virtualised deployment will 
eventually crash with (run tempest 2 times at least):
-  24096.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
+ To see the soft lockups, deploy a cloud on a virtualised env like ctsstack, 
run tempest on it, the compute nodes of the virtualised deployment will 
eventually stop responding with (run tempest 2 times at least):
+  24096.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
  [24124.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
  [24152.072002] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
  [24180.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
  [24208.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
  [24236.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
  [24264.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
  
  I am not sure whether the problem is that we are enabling KSM on a VM or
  the problem is that nested KSM is not behaving properly. Either way I
  can easily reproduce, please contact me if you need further details.

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https://bugs.launchpad.net/bugs/1413540

Title:
  qemu-kvm package enables KSM on VMs

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