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Table Of Contents
Modern Computer Architecture and Organization - Third Edition
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The hardware architectures of most general-purpose processor families have matured to the point where they fully support the execution of virtualized guest operating systems, at least in higher-end variants. The following sections introduce the virtualization capabilities provided by modern general-purpose processor families.
The x86 architecture was not initially designed to host virtualized operating systems. As a result, x86 processors, from the earliest days through the Pentium series, implemented instruction sets that contained several unsafe, non-trapping instructions. These instructions caused virtualization problems by, for example, allowing the guest operating system to access privileged registers that did not contain data corresponding to the virtual machine's state.
x86 current privilege level and unsafe instructions
In the x86 architecture, the lower two bits of the code segment (CS) register contain the current...