Server virtualization technologies for x86-based HP BladeSystem and HP ProLiant servers, 3rd edition

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Figure A2. In a virtual machine environment such as VMware ESX Server that uses binary translation, the guest
OS operates in ring 1 or ring 3.
Virtualization layer
Multitasking OS in a
virtual machine environment
Guest OS kernel
Guest application Guest application
Application
OS kernel/
device drivers
Ring 0
Ring 3
Typical multitasking
operating system
Processor
Ring 2
Ring 1
Processor
Guest OS kernel
With processor-assisted virtualization, hypervisor software will be able to run in a more privileged
ring layer. This will allow guest operating systems to run in their normal ring 0 layer. In addition,
AMD-V and Intel VT-x include new instructions that are specific to hypervisors. The combination of
these two factors (higher-privilege ring level and new hardware instructions) may provide a more
efficient way for hypervisors to virtualize server hardware.