Hypervisor Architectures

Definition

A hypervisor architecture describes where the virtualization layer sits relative to hardware and a general-purpose host OS. It is separate from the CPU or device virtualization technique.

The professor’s taxonomy

Architecture	Placement	Lecture examples	Design emphasis
Type 1	Directly on physical hardware	ESXi, Xen, Hyper-V	Server performance; hardware support and installation effort
Type 2	Application on a host OS	VirtualBox, VMware Workstation	Ease of installation/use; host-OS dependency
Hybrid	Virtualization integrated into host kernel	Linux KVM	Reuse OS services and drivers with kernel-level virtualization

Study diagrams

Type 1: guest -> hypervisor -> hardware
Type 2: guest -> hosted virtualization software -> host OS -> hardware
Hybrid: guest -> virtualization-enabled host kernel -> hardware
        userspace helpers provide additional services

These summarize placement, not every execution or I/O path.

KVM and taxonomy

The lecture explicitly calls KVM a hybrid approach, because Linux becomes the hypervisor through a kernel component and reuses existing drivers, scheduling, and memory management. Preserve this label when answering the professor’s taxonomy questions rather than silently substituting a different classification convention.

Hyper-V example in the deck

The professor explains that enabling Hyper-V places the Windows environment above its virtualization layer rather than leaving it as the bare-metal OS. Additional Hyper-V guests run alongside that environment in the illustrated model.

The associated Windows 10 and hypervisor-coexistence advice is slide-era context. Current compatibility or installation decisions would need a separate check.

Common mistakes

• Equating Type 1 with one particular CPU virtualization technique.
• Equating an architecture’s “hybrid” label with Lecture 02’s CPU-technique label.
• Treating all performance comparisons as absolute regardless of workload.
• Assuming a Type 1 design needs no OS-like services or hardware drivers.

Related: Virtual Machines and Hypervisors, QEMU and KVM, Hardware-Assisted Virtualization and VMCS, Nested Virtualization.

Source

Lecture 03 PDF pages 65-69 (printed slides 68-72). Context: Lecture 03 - Computing Virtualization Technologies and Tools. Diagrams and taxonomy cautions are study explanations.