EPT

最新推荐文章于 2022-02-21 16:54:30 发布

defeattroy

最新推荐文章于 2022-02-21 16:54:30 发布

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本文链接：https://blog.youkuaiyun.com/defeattroy/article/details/8778331

本文介绍了一种新的CPU机制——扩展页表(EPT)，该技术允许虚拟机保留对传统Intel 64位分页的控制权，并减少了从客户操作系统到VMM的虚拟机退出频率。EPT通过提供一种更高效的内存地址映射方式，从而降低了软件实现的页表虚拟化带来的开销。

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之前通过影子页表来处理虚拟机内存到物理内存的转换，现在用EPT

EPT: Extended Page Tables


VMM needs to retain control of physical-address space


page-table virtulization in software is a major source of overhead(namely soft MMU, or shaddow

page table ...)


EPT
 - new CPU mechanism for remapping guest-physical memory references
 - allow guest to retain control of legacy Intel 64 paging
 - Reduce fequency of VM exits to VMM




               CR3                                  EPT Base Pointer             
                |                                           |                         
                |     _______                               |                        
                `--> |Guest  |                           |---------|                   
                     |Intel64|    Guest Physical Addr    | Extended|     Host Physical Address
Guest Linear Addr -> |Page   | ------------------------> |   Page  |  ------------------------
                     |Tables |                           |  Tables |                      
                     |_______|                           |---------|                          
                          \                                  \                         
                           \                                  \                        
                            `controled by Guest                `controled by VMM           

EPT optionally activated on VM entry
 - when EPT active, EPT base pointer points to extended page tables
 - EPT deactivated on VM exit
 
Reference:
[1] Intel Virtualization Technology Processor Virtualization Extensions and Intel Trusted

execution Technology