From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jian Zhou Subject: Re: [PATCH] KVM: VMX: enable LBR virtualization Date: Fri, 16 Oct 2015 08:54:40 +0800 Message-ID: <56204AD0.7030509@huawei.com> References: <1444471906-8496-1-git-send-email-jianjay.zhou@huawei.com> <561BA323.7090002@huawei.com> <561BAB15.8090700@redhat.com> <561E3BDB.4080904@huawei.com> <561E3CC8.7080309@redhat.com> <561FAF51.4090101@huawei.com> <561FC028.8000006@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 7bit Cc: , To: Paolo Bonzini , , , , , , , , , Return-path: In-Reply-To: <561FC028.8000006@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org >>> 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. >> >> I think only for Linux guests. >> >> I googled how to enable LBR on other guests(except Linux guests), >> e.g. Windows, and got no developer manuals about it. >> >> Here is an article about it: >> http://www.codeproject.com/Articles/517466/Last-branch-records- >> and-branch-tracing >> it says: >> "bit 8 of DR7 represents bit 0 of DebugCtl. This is the LBR bit." > > Don't worry about the operating system in the guest: you are just > emulating a processor feature, you do not care about anything except > what is written in the Intel SDM. > > You can use kvm-unit-tests > (https://git.kernel.org/cgit/virt/kvm/kvm-unit-tests.git/) to write a > test for your feature. There are existing tests for debugging features. ok. Regards, Jian > > >