5.3 z/VM security features z/VM is today's version of a hypervisor operating system. Virtual machine design began in the early 1960s, when IBM was exploring how to meet customer expectations using virtualization. The development of virtual machines was closely tied to the development of virtual storage, because they needed to operate together. The core of z/VM (that is, the hypervisor) is the control program . The control program creates and maintains virtual environments for virtual machines (guests). Figure 5-2 represents a z/VM system with multiple guests. z/VM CP z/VM guest IPL and resident z/OS Guest VM VM Guest VM Linux Guest VM Linux Guest VM Linux Guest VM Linux Guest VM z/OS CP virtual devices virtual devices Linux Linux Linux Linux z/VM guest IPL and resident virtual devices virtual devices virtual devices virtual devices Guest "minidisks" Guest OS operators Guest LAN IUCV VCTC VLAN HiperSockers z/VM guest IPL and resident PCI Crypto FICON Channel OSA Express IFL zSeries hardware