linux-kernel - Re: [PATCH 1/4] KVM: nVMX: support restore of VMX capability MSRs

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Message-ID: <CALzav=cHZJcasS+aSYmuXv-RhO4AAUFTNOYDyViaoay19=rOeQ@mail.gmail.com>
Date:   Mon, 28 Nov 2016 13:11:55 -0800
From:   David Matlack <dmatlack@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 1/4] KVM: nVMX: support restore of VMX capability MSRs

On Wed, Nov 23, 2016 at 3:44 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
> On 23/11/2016 02:14, David Matlack wrote:
>>       switch (msr_index) {
>>       case MSR_IA32_VMX_BASIC:
>> +             return vmx_restore_vmx_basic(vmx, data);
>> +     case MSR_IA32_VMX_TRUE_PINBASED_CTLS:
>> +     case MSR_IA32_VMX_PINBASED_CTLS:
>> +     case MSR_IA32_VMX_TRUE_PROCBASED_CTLS:
>> +     case MSR_IA32_VMX_PROCBASED_CTLS:
>> +     case MSR_IA32_VMX_TRUE_EXIT_CTLS:
>> +     case MSR_IA32_VMX_EXIT_CTLS:
>> +     case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
>> +     case MSR_IA32_VMX_ENTRY_CTLS:
>
> PINBASED_CTLS, PROCBASED_CTLS, EXIT_CTLS and ENTRY_CTLS can be derived
> from their "true" counterparts, so I think it's better to remove the
> "non-true" ones from struct nested_vmx (and/or add the "true" ones when
> missing) and make them entirely computed.  But it can be done on top.

Good point. And that would mean userspace does not need to restore the
non-true MSRs, right? KVM does not emulate MSR_IA32_VMX_BASIC[55]=0,
and will probably never want to.