The vhba module proxies SCSI commands to the physical SCSI HBA driver that is associated with the virtual SAN's SCSI initiator port.
The scsi_vhci driver, which implements Oracle Solaris I/O multipathing, handles reservation persistency during path failover for both SCSI-2 reservations and SCSI-3 reservations. The vhba module plugs in to the Oracle Solaris I/O framework and thus supports SCSI reservations by leveraging the scsi_vhci support.