From: Jian Zhou <jianjay.zhou@huawei.com>
To: Paolo Bonzini <pbonzini@redhat.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: Fri, 16 Oct 2015 08:54:40 +0800 [thread overview]
Message-ID: <56204AD0.7030509@huawei.com> (raw)
In-Reply-To: <561FC028.8000006@redhat.com>
>>> 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
>
>
>
prev parent reply other threads:[~2015-10-16 0:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1444471906-8496-1-git-send-email-jianjay.zhou@huawei.com>
2015-10-12 12:10 ` [PATCH] KVM: VMX: enable LBR virtualization Jian Zhou
2015-10-12 12:44 ` Paolo Bonzini
2015-10-14 11:26 ` Jian Zhou
2015-10-14 11:30 ` Paolo Bonzini
2015-10-15 13:51 ` Jian Zhou
2015-10-15 15:03 ` Paolo Bonzini
2015-10-16 0:54 ` Jian Zhou [this message]
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