How does XEN work without VHE on ARM?

XEN has support for ARM and it is also possible to run it on a cpu without VHE (virtual hardware extension) cap that was introduced with ARMV8.1-A extension. As I understand linux kernel of a guest vm communicates with xen hypervisor over HVC calls. HVC call is a hardware feature, as I think only available in VHE enabled system. But how does it work without VHE? Also with HVCs but as some kind of software call? Please correct me if I'm wrong in my understanding.