From mboxrd@z Thu Jan  1 00:00:00 1970
From: Naresh Rapolu <nrapolu@purdue.edu>
Subject: boot_cpu_data differs between Xen hypervisor boot and
 normal pv_ops kernel boot
Date: Wed, 31 Mar 2010 11:29:04 -0400
Message-ID: <4BB36A40.1080903@purdue.edu>
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Hello,

After booting  the  xen-stable 2.6.32.10 pv_ops kernel from jeremy git 
tree  with Xen-4.0.0-rc8 installed,
dmesg | grep PMU  shows :

Performance Events : unsupported p6 CPU model 26 no PMU driver, software 
events only.
PMU:oprofile: found i386/core_i7.

If I boot the same compiled kernel, without Xen installed, dmesg | grep 
PMU shows :
Performance Events : Nehalem/Corei7 events, Intel PMU driver.
PMU:oprofile: found i386/core_i7.


When I looked into the source code,  arch/x86/kernel/cpu/perf_event.c,   
at run-time boot_cpu_data  structure seems to differ  in these two forms 
of booting.
Due to this, Iam not able to use the hardware performance counters in  
my Xeon 5530 processor  as  hardware events(cache-misses etc) are being 
disabled.

Is there any reason for this ?

Any help is appreciated.
Thanks,
Naresh Rapolu.