From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: VMX: enable LBR virtualization Date: Wed, 14 Oct 2015 13:30:16 +0200 Message-ID: <561E3CC8.7080309@redhat.com> References: <1444471906-8496-1-git-send-email-jianjay.zhou@huawei.com> <561BA323.7090002@huawei.com> <561BAB15.8090700@redhat.com> <561E3BDB.4080904@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 7bit Cc: weidong.huang@huawei.com, peter.huangpeng@huawei.com To: Jian Zhou , 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 Return-path: In-Reply-To: <561E3BDB.4080904@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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