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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: kvm <kvm@vger.kernel.org>,
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Subject: Re: [RFC 0/6] Enlightened VMCS support for KVM on Hyper-V
References: <20180115173105.31845-1-vkuznets@redhat.com>
        <CANRm+Cza82KuvEQQi=2Zio2u0EHm1kfPfr=aOhoLdra+fpB2Wg@mail.gmail.com>
Date: Tue, 16 Jan 2018 13:05:26 +0100
In-Reply-To: <CANRm+Cza82KuvEQQi=2Zio2u0EHm1kfPfr=aOhoLdra+fpB2Wg@mail.gmail.com>
        (Wanpeng Li's message of "Tue, 16 Jan 2018 09:21:04 +0800")
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Wanpeng Li <kernellwp@gmail.com> writes:

> 2018-01-16 1:30 GMT+08:00 Vitaly Kuznetsov <vkuznets@redhat.com>:
>> Early RFC. I'll refer to this patchset in my DevConf/FOSDEM
>> presentations.
>>
>> When running nested KVM on Hyper-V it's possible to use so called
>> 'Enlightened VMCS' and do normal memory reads/writes instead of
>> doing VMWRITE/VMREAD instructions. Tests show that this speeds up
>> tight CPUID loop almost 3 times:
>>
>> Before:
>> ./cpuid_tight
>> 20459
>>
>> After:
>> ./cpuid_tight
>> 7698
>
> Maybe you can apply a similar idea to kvm nested on kvm.
>

Yes we can. Basically, that would mean directly accessing 'struct
vmcs12' from L1 hypervisor.

-- 
  Vitaly