Hypervisorlevel

Hypervisor level refers to the privilege layer at which virtualization software called a hypervisor operates within a computer system. It is the layer that sits between the hardware and the virtual machines, and it is typically more trusted and more privileged than the guest operating systems running inside the VMs. In modern architectures with hardware-assisted virtualization, the hypervisor controls access to hardware resources and mediates all interactions between guests and the physical device.

On x86 and similar architectures, this privilege distinction is implemented through distinct processor modes. The hypervisor runs in a root or privileged mode (for example VMX root mode or ring -1), while each guest runs in a non-root mode. The hypervisor intercepts privileged instructions and handles VM exits to provide virtualization with minimal guest involvement.

Hypervisor deployment models are typically categorized as Type 1 and Type 2. Type 1 hypervisors operate directly on the hardware and manage guests without a host operating system, giving the hypervisor the highest level of control. Type 2 hypervisors run as software on a host operating system; the host OS owns the hardware and provides resources to the hypervisor and its guests.

Responsibilities at the hypervisor level include scheduling of virtual machines, memory management and isolation (often via nested paging or extended page tables), I/O virtualization, and device emulation. The hypervisor also implements the VM lifecycle, manages checkpoints or migrations, and enforces isolation between guests.

Because the hypervisor sits at a privileged level, its security and reliability are critical. A compromised hypervisor undermines all hosted VMs. Modern designs aim for a minimal trusted computing base, strong isolation, and auditable management interfaces.