虚拟化不等于虚拟机不等于Hypervisor，定义如下
The primary way the OS does this is through a general technique that we call virtualization. That is, the OS takes a physical resource (such as the processor, or memory, or a disk) and transforms it into a more general, powerful, and easy-to-use virtual form of itself. Thus, we sometimes refer to the operating system as a virtual machine.
2.1. 虚拟化CPU
简要地说，就是让一个CPU可以"同时执行"多个程序，看起来好像有多个CPU似的。听起来很像并发？是的！跟并发有很大的交集。
2.2. 虚拟化内存
可以看到两个程序在对同一个指针 0x200000 操作。这是正确的，因为它们有各自的地址空间，并不共享同一块物理内存。
让一个内存可以看起来像有多个内存似的。
2.3. 并发 (Concurrency)
标签：二章,虚拟化,virtual,笔记,并发,内存,OSTEP,CPU From： https://www.cnblogs.com/yinhuachen/p/16926832.html