* PMU in KVM
@ 2013-11-26 8:02 Arthur Chunqi Li
2013-11-26 9:08 ` Gleb Natapov
0 siblings, 1 reply; 2+ messages in thread
From: Arthur Chunqi Li @ 2013-11-26 8:02 UTC (permalink / raw
To: kvm, Gleb Natapov
Hi Gleb,
I noticed that arch/x86/kvm/pmu.c is on your management and I have
some questions about PMU in KVM. Thanks ahead if you can spare time
answering these questions.
1. How could PMU cooperate with Intel VT? For example, I only find
flags in IA32_PERFEVTSELx MSRs to count in OS and USER mode (Ring 0
and other rings). What is the consequence when I open VMXON with PMU
enabled? Can I distinguish the counts in root and non-root mode? I
cannot find the related descriptions in Intel manual.
2. What is the current status of vPMU in KVM? Is it auto-enabled? And
how can I use (or enable/disable) it?
Thanks,
Arthur
--
Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: PMU in KVM
2013-11-26 8:02 PMU in KVM Arthur Chunqi Li
@ 2013-11-26 9:08 ` Gleb Natapov
0 siblings, 0 replies; 2+ messages in thread
From: Gleb Natapov @ 2013-11-26 9:08 UTC (permalink / raw
To: Arthur Chunqi Li; +Cc: kvm
On Tue, Nov 26, 2013 at 04:02:36PM +0800, Arthur Chunqi Li wrote:
> Hi Gleb,
>
> I noticed that arch/x86/kvm/pmu.c is on your management and I have
> some questions about PMU in KVM. Thanks ahead if you can spare time
> answering these questions.
>
> 1. How could PMU cooperate with Intel VT? For example, I only find
> flags in IA32_PERFEVTSELx MSRs to count in OS and USER mode (Ring 0
> and other rings). What is the consequence when I open VMXON with PMU
> enabled? Can I distinguish the counts in root and non-root mode? I
> cannot find the related descriptions in Intel manual.
>
No you cannot. You can disable/enable PMU counters before/after
vmexit/vmentry and in this way know in what sate event was counted. That
what MPU emulation does.
> 2. What is the current status of vPMU in KVM? Is it auto-enabled? And
> how can I use (or enable/disable) it?
>
If you run with -cpu host on Intel machine it will be enabled.
--
Gleb.
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