linux-kernel - Re: [PATCH 2/5] KVM: nVMX: Verify the VMX controls MSRs with the global capability when setting VMX MSRs

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Message-ID: <d80093d9-3368-adc7-050c-75686cd261ec@intel.com>
Date:   Mon, 31 Aug 2020 11:15:50 +0800
From:   Chenyi Qiang <chenyi.qiang@...el.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] KVM: nVMX: Verify the VMX controls MSRs with the
 global capability when setting VMX MSRs



On 8/29/2020 2:23 AM, Jim Mattson wrote:
> On Fri, Aug 28, 2020 at 1:54 AM Chenyi Qiang <chenyi.qiang@...el.com> wrote:
>>
>> When setting the nested VMX MSRs, verify it with the values in
>> vmcs_config.nested_vmx_msrs, which reflects the global capability of
>> VMX controls MSRs.
>>
>> Signed-off-by: Chenyi Qiang <chenyi.qiang@...el.com>
> 
> You seem to have entirely missed the point of this code, which is to
> prevent userspace from adding features that have previously been
> removed for this vCPU (e.g as a side-effect of KVM_SET_CPUID).
> 

We only have the case that the scope of features set by userspace is 
always reduced, right? If so, we don't need the change here.