The hypervisor is responsible for controlling and executing each of the domains and runs with full privileges. The control tools for managing the domains run under the specialized control domain domain 0 (dom0).
The hypervisor virtualizes the system's hardware. The hypervisor transparently shares and partitions the system's CPUs, memory, and NIC resources among the user domains. The hypervisor performs the low-level work required to provide a virtualized platform for operating systems.
The hypervisor relies primarily on the control domain for the following:
Which guest domains are created.
Which resources the guest domains can access.
How much memory a given guest domain can have.
Which devices a guest domain can access, because xVM does not include any device drivers. The hypervisor delegates control of the machine's physical devices to the control domain, domain 0.
Thus, by default, only the control domain has access to physical devices. The guest domains running on the host are presented with virtualized devices. The domain interacts with the virtualized devices in the same way that the domain would interact with the physical devices. Also see Resource Virtualization to Enable Interoperability.
The following figure shows the Sun xVM hypervisor configuration.