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Hardware virtualization is the virtualization of computers as complete hardware platforms, certain logical abstractions of their componentry, or only the functionality required to run various operating systems. Virtualization emulates the hardware environment of its host architecture, allowing multiple OSes to run unmodified and in isolation.
Instruction set extensions that have been added to the x86 instruction set in order to support hardware virtualization.These extensions provide instructions for entering and leaving a virtualized execution context and for loading virtual-machine control structures (VMCSs), which hold the state of the guest and host, along with fields which control processor behavior within the virtual machine.
x86 virtualization is the use of hardware-assisted virtualization capabilities on an x86/x86-64 CPU.. In the late 1990s x86 virtualization was achieved by complex software techniques, necessary to compensate for the processor's lack of hardware-assisted virtualization capabilities while attaining reasonable performance.
In hardware-assisted virtualization, the hardware provides architectural support that facilitates building a virtual machine monitor and allows guest OSes to be run in isolation. [19] Hardware-assisted virtualization was first introduced on the IBM System/370 in 1972, for use with VM/370 , the first virtual machine operating system offered by ...
To derive their virtualization theorems, which give sufficient (but not necessary) conditions for virtualization, Popek and Goldberg introduce a classification of some instructions of an ISA into 3 different groups: Privileged instructions Those that trap if the processor is in user mode and do not trap if it is in system mode (supervisor mode).
In mediated device pass-through or full GPU virtualization, the GPU hardware provides contexts with virtual memory ranges for each guest through IOMMU and the hypervisor sends graphical commands from guests directly to the GPU. This technique is a form of hardware-assisted virtualization and achieves near-native [b] performance and high ...
Full virtualization – Almost complete virtualization of the actual hardware to allow software environments, including a guest operating system and its apps, to run unmodified. Paravirtualization – The guest apps are executed in their own isolated domains, as if they are running on a separate system, but a hardware environment is not simulated.
To use virtual 8086 mode, an operating system sets up a virtual 8086 mode monitor, which is a program that manages the real-mode program and emulates or filters access to system hardware and software resources. The monitor must run at privilege level 0 and in protected mode. Only the 8086 program runs in VM86 mode and at privilege level 3.