Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs()

[Sean Christopherson]

On Mon, Jan 27, 2020 at 04:38:27PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@xxxxxxxxx> writes:
> > One last idea, can we keep the MSR filtering as is and add the hack in
> > vmx_restore_control_msr()?  That way the (userspace) host and guest see
> > the same values when reading the affected MSRs, and eVMCS wouldn't need
> > it's own hook to do consistency checks.
> 
> Yes but (if I'm not mistaken) we'll have then to keep the filtering we
> currently do in nested_enable_evmcs(): if userspace doesn't do
> KVM_SET_MSR for VMX MSRs (QEMU<4.2) then the filtering in
> vmx_restore_control_msr() won't happen and the guest will see the
> unfiltered set of controls...

Ya, my thought was to add this on top of the nested_enable_evmcs() code.