linux-kernel - Hardware performance events are not counted by "perf" in a 2.6.31.12 KVM guest

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Date:	Fri, 26 Mar 2010 22:03:10 -0400
From:	Naresh Rapolu <nrapolu@...due.edu>
To:	linux-kernel@...r.kernel.org
Subject: Hardware performance events are not counted by  "perf"   in a 2.6.31.12
  KVM guest

Hello,

"perf"  tool does not count  hardware performance events ( cache misses 
etc) in a  KVM guest ( Ubuntu 9.10 karmic,  2.6.31-14-generic  kernel) 
on  Xeon 5530 quad-core.  The host  is  2.6.28  kernel , Ubuntu 8.04 
LTS, Hardy.

readfile.sh  reads in a  large file (1430 lines),  which should cause  
cache-misses.
root@...ticore4-vm3:/usr/src/linux-2.6.31.12/tools/perf# ./perf stat -r 
5 -- bash readfile.sh

Performance counter stats for 'bash readfile.sh' (5 runs):

  11002.207467  task-clock-msecs         #      1.042 CPUs    ( +-  
10.834% )
          3480  context-switches                 #      0.000 M/sec   ( 
+-  19.017% )
          2238  CPU-migrations                 #      0.000 M/sec   ( 
+-  29.488% )
        482299  page-faults                      #      0.044 M/sec   ( 
+-   0.141% )
             0  cycles                                  #      0.000 
M/sec   ( +-     nan% )
             0  instructions                          #        nan 
IPC     ( +-     nan% )
             0  cache-references                 #      0.000 M/sec   ( 
+-     nan% )
             0  cache-misses                      #      0.000 M/sec   ( 
+-     nan% )

  10.560510393  seconds time elapsed   ( +-  11.401% )

Do I need to make some configuration changes to enable hardware events 
?  A similar question was posted recently here : 
http://lkml.org/lkml/2010/3/18/342   but no response !
Any help would be greatly appreciated.

Thanks,
Naresh Rapolu.
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