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Subject: Re: [PATCH 1/5] KVM: nVMX: Fix VMX controls MSRs setup when nested
 VMX enabled
To:     Chenyi Qiang <chenyi.qiang@intel.com>,
        Jim Mattson <jmattson@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>, kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20200828085622.8365-1-chenyi.qiang@intel.com>
 <20200828085622.8365-2-chenyi.qiang@intel.com>
 <CALMp9eThyqWuduU=JN+w3M3ANeCYN+7=s-gippzyu_GmvgtVGA@mail.gmail.com>
 <534a4ad5-b083-1278-a6ac-4a7e2b6b1600@intel.com>
From:   Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <1fbfb77d-4f28-bcb6-a95c-f4ac7a313d2d@intel.com>
Date:   Sat, 29 Aug 2020 10:51:47 +0800
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On 8/29/2020 9:49 AM, Chenyi Qiang wrote:
> 
> 
> On 8/29/2020 1:43 AM, Jim Mattson wrote:
>> On Fri, Aug 28, 2020 at 1:54 AM Chenyi Qiang <chenyi.qiang@intel.com> 
>> wrote:
>>>
>>> KVM supports the nested VM_{EXIT, ENTRY}_LOAD_IA32_PERF_GLOBAL_CTRL and
>>> VM_{ENTRY_LOAD, EXIT_CLEAR}_BNDCFGS, but they doesn't expose during
>>> the setup of nested VMX controls MSR.
>>>
>>
>> Aren't these features added conditionally in
>> nested_vmx_entry_exit_ctls_update() and
>> nested_vmx_pmu_entry_exit_ctls_update()?
>>
> 
> Yes, but I assume vmcs_config.nested should reflect the global 
> capability of VMX MSR. KVM supports these two controls, so should be 
> exposed here.

No. I prefer to say they are removed conditionally in 
nested_vmx_entry_exit_ctls_update() and 
nested_vmx_pmu_entry_exit_ctls_update().

Userspace calls vmx_get_msr_feature() to query what KVM supports for 
these VMX MSR. In vmx_get_msr_feature(), it returns the value of 
vmcs_config.nested. As KVM supports these two bits, we should advertise 
them in vmcs_config.nested and report to userspace.