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[Xen-devel] boot_cpu_data differs between Xen hypervisor boot and normal

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] boot_cpu_data differs between Xen hypervisor boot and normal pv_ops kernel boot
From: Naresh Rapolu <nrapolu@xxxxxxxxxx>
Date: Wed, 31 Mar 2010 11:29:04 -0400
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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.

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