Re: [PATCH] KVM: VMX: enable LBR virtualization

From	Paolo Bonzini <pbonzini@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] KVM: VMX: enable LBR virtualization
Date	2015-10-14 13:40 +0200
Message-ID	<qjszv-5BO-5@gated-at.bofh.it> (permalink)
References	<qiKf8-74w-15@gated-at.bofh.it> <qiKf8-74w-13@gated-at.bofh.it> <qiKIa-7EQ-23@gated-at.bofh.it> <qjspS-5qz-49@gated-at.bofh.it>
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On 14/10/2015 13:26, Jian Zhou wrote:
> On 12/10/2015 20:44, Paolo Bonzini wrote:
>> In addition, the MSR numbers may differ between the guest and the host,
>> because it is possible to emulate e.g. a Core CPU on a Core 2 CPU.  So I
>> recommend against using the atomic switch mechanism for the from/to MSRs.
> 
>   The vLBR feature depends on vPMU, and to enable vPMU, it needs to
>   specify the "cpu mode" in the guest XML as host-passthrough. I think
>   the MSR numbers between the guest and the host are the same in this
>   senario.

Does it depend on vPMU _for Linux guests_ or in general?  My impression
is that LBR can be used by the guest independent of the PMU.  You should
also write a unit test for kvm-unit-tests to test the behavior of your
implementation.

Thanks,

Paolo
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Thread

Re: [PATCH] KVM: VMX: enable LBR virtualization Jian Zhou <jianjay.zhou@huawei.com> - 2015-10-12 14:20 +0200
  Re: [PATCH] KVM: VMX: enable LBR virtualization Paolo Bonzini <pbonzini@redhat.com> - 2015-10-12 14:50 +0200
    Re: [PATCH] KVM: VMX: enable LBR virtualization Jian Zhou <jianjay.zhou@huawei.com> - 2015-10-14 13:30 +0200
      Re: [PATCH] KVM: VMX: enable LBR virtualization Paolo Bonzini <pbonzini@redhat.com> - 2015-10-14 13:40 +0200
        Re: [PATCH] KVM: VMX: enable LBR virtualization Jian Zhou <jianjay.zhou@huawei.com> - 2015-10-15 16:00 +0200
          Re: [PATCH] KVM: VMX: enable LBR virtualization Paolo Bonzini <pbonzini@redhat.com> - 2015-10-15 17:10 +0200
            Re: [PATCH] KVM: VMX: enable LBR virtualization Jian Zhou <jianjay.zhou@huawei.com> - 2015-10-16 03:00 +0200

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