From: Gleb Natapov <gleb@redhat.com>
To: Arthur Chunqi Li <yzt356@gmail.com>
Cc: kvm <kvm@vger.kernel.org>
Subject: Re: PMU in KVM
Date: Tue, 26 Nov 2013 11:08:23 +0200 [thread overview]
Message-ID: <20131126090823.GG959@redhat.com> (raw)
In-Reply-To: <CABpY8MKWsw+7TxpQ+c9YSra56q0KM8kKD2VUKuMJBJYoU5sk8w@mail.gmail.com>
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.
prev parent reply other threads:[~2013-11-26 9:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-26 8:02 PMU in KVM Arthur Chunqi Li
2013-11-26 9:08 ` Gleb Natapov [this message]
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