Re: [PATCH 2/4] KVM: nVMX: Make VMPTRST return eVMCS GPA when it is used

On Fri, Aug 14, 2026, [email protected] wrote:
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index c78c67525ac9b..d13a4d47bc68f 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> [ ... ]
> > @@ -5958,8 +5958,14 @@ static int handle_vmptrst(struct kvm_vcpu *vcpu)
> >  	if (!nested_vmx_check_permission(vcpu))
> >  		return 1;
> >  
> > -	if (unlikely(nested_vmx_is_evmptr12_valid(to_vmx(vcpu))))
> > -		return 1;
> > +	/*
> > +	 * Hyper-V TLFS does not specify the behavior of VMPTRST when eVMCS is used
> > +	 * but genuine Hyper-V seems to be returning eVMCS GPA.
> > +	 */
> > +	if (nested_vmx_is_evmptr12_valid(to_vmx(vcpu)))
> > +		current_vmptr = to_vmx(vcpu)->nested.hv_evmcs_vmptr;
> 
> [Severity: Low]
> Will this cause a build failure when CONFIG_KVM_HYPERV is disabled?
> 
> Because nested_vmx_is_evmptr12_valid() is a static inline function rather
> than a preprocessor macro, the compiler still evaluates and type-checks
> this branch even when the helper is hardcoded to return false. If the
> hv_evmcs_vmptr member in struct nested_vmx is conditionally compiled based
> on CONFIG_KVM_HYPERV, the compiler will fail to find it here.

Yep.

arch/x86/kvm/vmx/nested.c: In function ‘handle_vmptrst’:
arch/x86/kvm/vmx/nested.c:5971:53: error: ‘struct nested_vmx’ has no member named ‘hv_evmcs_vmptr’
 5971 |                 current_vmptr = to_vmx(vcpu)->nested.hv_evmcs_vmptr;
      |                                                     ^