Re: [PATCH v2 05/16] KVM: VMX: Drop initialization of IA32_FEATURE_CONTROL MSR

[Paolo Bonzini]

On 22/10/19 02:08, Sean Christopherson wrote:
> Remove the code to initialize IA32_FEATURE_CONTROL MSR when KVM is
> loaded now that the MSR is initialized during boot on all CPUs that
> support VMX, i.e. can possibly load kvm_intel.
> 
> Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
>  arch/x86/kvm/vmx/vmx.c | 48 +++++++++++++++++-------------------------
>  1 file changed, 19 insertions(+), 29 deletions(-)

I am still not sure about this...  Enabling VMX is adding a possible
attack vector for the kernel, we should not do it unless we plan to do a
VMXON.  Why is it so important to operate with locked
IA32_FEATURE_CONTROL (so that KVM can enable VMX and the kernel can
still enable SGX if desired).

Paolo