From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: How to know that vPMU is enabled or disabled?
Date: Tue, 24 Jun 2014 22:38:11 +0200
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To: Jidong Xiao <jidong.xiao@gmail.com>, KVM <kvm@vger.kernel.org>
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Il 24/06/2014 10:33, Jidong Xiao ha scritto:
> I think I have figured out this. According to this patch (as well as
> the Intel SDM manual), it looks like pmu is exposed via the cpuid leaf
> 0xah.
>
> https://github.com/torvalds/linux/commit/a6c06ed1a60aff77b27ba558c315c3fed4e35565
>
> Therefore, in the guest os, one can run the cpuid instruction with
> leaf 0xa, and if vpmu is supported/enabled, the return value in
> eax/ebx/ecx/edx should be something non-zero, and in the cloud machine
> which I am using I see these registers are all zero, therefore I think
> vpmu is not supported in my virtual machine. Probably it is masked by
> Qemu.

This is correct.  QEMU only enables vPMU if you use "-cpu host".

Paolo