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From: Paolo Bonzini <pbonzini@redhat.com>
To: Jian Zhou <jianjay.zhou@huawei.com>,
	herongguang.he@huawei.com, zhang.zhanghailiang@huawei.com,
	gleb@kernel.org, tglx@linutronix.de, mingo@redhat.com,
	hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: weidong.huang@huawei.com, peter.huangpeng@huawei.com
Subject: Re: [PATCH] KVM: VMX: enable LBR virtualization
Date: Wed, 14 Oct 2015 13:30:16 +0200	[thread overview]
Message-ID: <561E3CC8.7080309@redhat.com> (raw)
In-Reply-To: <561E3BDB.4080904@huawei.com>



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

  reply	other threads:[~2015-10-14 11:30 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-10 10:11 [PATCH] KVM: VMX: enable LBR virtualization Jian Zhou
2015-10-12 12:10 ` Jian Zhou
2015-10-12 12:44   ` Paolo Bonzini
2015-10-14 11:26     ` Jian Zhou
2015-10-14 11:30       ` Paolo Bonzini [this message]
2015-10-15 13:51         ` Jian Zhou
2015-10-15 15:03           ` Paolo Bonzini
2015-10-16  0:54             ` Jian Zhou

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