linux-kernel - Re: [PATCH 0/5] KVM: SVM: nSVM: Implement Enlightened MSR-Bitmap for Hyper-V-on-KVM and fix it for KVM-on-Hyper-V

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Date:   Wed, 02 Feb 2022 10:52:55 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] KVM: SVM: nSVM: Implement Enlightened MSR-Bitmap
 for Hyper-V-on-KVM and fix it for KVM-on-Hyper-V

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 2/1/22 19:58, Vitaly Kuznetsov wrote:
>>> Hmm, it fails to compile with CONFIG_HYPERV disabled, and a trivial
>>> #if also fails due to an unused goto label.  Does this look good to you?
>>>
>> Hm, it does but honestly I did not anticipate this dependency --
>> CONFIG_HYPERV is needed for KVM-on-Hyper-V but this feature is for
>> Hyper-V-on-KVM. Let me take a look tomorrow.
>> 
>
> It's because, without it, the relevant structs are not defined by 
> svm_onhyperv.h.  Go ahead and send a new version if you prefer

Should be fixed in v2. I still think it makes sense to keep this
KVM-on-Hyper-V and Hyper-V-on-KVM separation as it's really confusing to
an unprepared reader. There's still room for improvement in nVMX I
believe but it's orthogonal to this nSVM feature.

-- 
Vitaly