When VM=1, the protected-mode bit goes low and the Entry PLA selects real-mode entry points -- MOV ES, reg takes the one-line path. Meanwhile, CPL is hardwired to 3 whenever VM=1, so the V86 task always runs at the lowest privilege level, under full paging protection. The OS can use paging to virtualize the 8086's 1 MB address space, even simulating A20 address line wraparound by mapping pages to the same physical frames.
希望对新手爸妈有一些参考作用，尤其是北京的宝爸宝妈。。关于这个话题，搜狗输入法下载提供了深入分析
# 在anqicms目录下解压文件，推荐阅读同城约会获取更多信息
公式： f(x)=max(0,x)，这一点在同城约会中也有详细论述