linux-kernel - Re: [PATCH v3 0/6] KVM: nVMX: Enlightened VMCS for Hyper-V on KVM

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Date:   Thu, 2 Aug 2018 14:45:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Cathy Avery <cavery@...hat.com>, linux-kernel@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH v3 0/6] KVM: nVMX: Enlightened VMCS for Hyper-V on KVM

On 25/07/2018 18:30, Vitaly Kuznetsov wrote:
> Changes since v2:
> - Rebase to the current kvm/queue.
> - Simplify clean fields check in prepare_vmcs02{,_full} and
>   copy_enlightened_to_vmcs12() by resetting the clean fields mask in
>   nested_vmx_handle_enlightened_vmptrld() when we switch from one L2 guest
>   to another [Paolo Bonzini]
> - Cope with the newly introduced vmx_get_nested_state() by returning
>   -ENOTSUPP when eVMCS is in use. We'll do proper nested state save/restore
>   later.

Looks good, but we have to do something about live migration.  Perhaps
you can write a testcase analogous to the new state_test, that tests
eVMCS in general before we have support in QEMU.

Thanks,

Paolo

> Description:
> 
> This is an initial implementation of Enlightened VMCS for nested Hyper-V on
> KVM. Using it helps to spare 1500 cpu cycles for nested vmexit (tight cpuid
> loop in WS2016 with Hyper-V role on KVM: 15200 cycles -> 13700 cycles).
> 
> Ladi Prosek (1):
>   KVM: hyperv: define VP assist page helpers
> 
> Vitaly Kuznetsov (5):
>   KVM: VMX: refactor evmcs_sanitize_exec_ctrls()
>   KVM: nVMX: add KVM_CAP_HYPERV_ENLIGHTENED_VMCS capability
>   KVM: nVMX: add enlightened VMCS state
>   KVM: nVMX: implement enlightened VMPTRLD and VMCLEAR
>   KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case
> 
>  arch/x86/include/asm/kvm_host.h |   3 +
>  arch/x86/kvm/hyperv.c           |  23 +-
>  arch/x86/kvm/hyperv.h           |   4 +
>  arch/x86/kvm/lapic.c            |   4 +-
>  arch/x86/kvm/lapic.h            |   2 +-
>  arch/x86/kvm/svm.c              |   9 +
>  arch/x86/kvm/vmx.c              | 824 +++++++++++++++++++++++++++++++++-------
>  arch/x86/kvm/x86.c              |  17 +-
>  include/uapi/linux/kvm.h        |   1 +
>  9 files changed, 737 insertions(+), 150 deletions(-)
>