x86/kvm/nVMX: don't skip emulated instruction twice when vmptr address is not backed

Since commit 09abb5e3 ("KVM: nVMX: call kvm_skip_emulated_instruction
in nested_vmx_{fail,succeed}") nested_vmx_failValid() results in
kvm_skip_emulated_instruction() so doing it again in handle_vmptrld() when
vmptr address is not backed is wrong, we end up advancing RIP twice.

Fixes: fca91f6d ("kvm: nVMX: Set VM instruction error for VMPTRLD of unbacked page")
Reported-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: NSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -4540,9 +4540,8 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 			 * given physical address won't match the required
 			 * VMCS12_REVISION identifier.
 			 */
-			nested_vmx_failValid(vcpu,
+			return nested_vmx_failValid(vcpu,
 				VMXERR_VMPTRLD_INCORRECT_VMCS_REVISION_ID);
-			return kvm_skip_emulated_instruction(vcpu);
 		}
 		new_vmcs12 = kmap(page);
 		if (new_vmcs12->hdr.revision_id != VMCS12_REVISION ||