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Re: [Xen-devel] Virtualization of the CPU Performance Monitoring Unit

On Sat, Apr 7, 2012 at 12:43 AM, Wei Huang <wei.huang2@xxxxxxx> wrote:
> On 04/06/2012 10:41 AM, Lin Ming wrote:
>> Hi list,
>> Is anybody working on virtualization of the CPU Performance Monitoring
>> Unit?
>> There are 2 PMU related projects listed on GSoC 2012 page.
>> http://wiki.xen.org/wiki/Archived/GSoC_2012_Ideas
>> - Virtualization of the CPU Performance Monitoring Unit
>> - Perf support for Xen
>> I'm interested on these 2 projects.
> Hi Lin,
> 1. I don't think Xen was accepted as an organization for 2012 GSOC. See
> http://lists.xen.org/archives/html/xen-devel/2012-03/msg02080.html.

It doesn't matter.
I just want to find something valuable to do.

> 2. The PMU project description in the wiki is vague. I know HVM guests
> support virtualized PMU. Please check vpmu.c files in /hvm, /svm, and /vmx
> directories. You better ask mentors for details (maybe this is XCP
> specific?).

(CC mentors)

I tested PMU/Perf support with xen-unstable, dom0 3.3 kernel, domU
3.4-rc1 kernel.
Here is the result on an Intel SandyBrige machine.

- In dom0

# dmesg |grep -i "Performance Event"
Performance Events: unsupported p6 CPU model 42 no PMU driver,
software events only.

Hardware events are not supported yet in dom0.

- In domU
# dmesg |grep -i "Performance Events"
Performance Events: 16-deep LBR, SandyBridge events, Intel PMU driver.

Seems domU has support for hardware events.
But "perf" does not work on domU.
Run "perf top", but no data was collected.

# cat /proc/interrupts |grep "PMI"
 PMI:          0          0   Performance monitoring interrupts

No PMU interrupts.

BTW, I also tested KVM-Qemu.
"perf" works well on KVM-Qemu.

Lin Ming

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