Linux Virtualization with Lguest

 摘自Linux Virtualization with Lguest，Author：John Quigley

Lguest Launcher 

Launcher is an ELF userspace app that launches and monitors guests。

它執行以下任務： 

1. maps guest kernel imagine into host’s memory

2.opens /dev/lguest and writes config info about guest

3.hypervisor uses this to initialize and launch guest

4.open procfile used for ongoing control, console I/O,DMA-like I/O via shmem 

注意: Physical memory in the Guest is the Host’s virtual memory.  

Lguest Hypervisor  

The hypervisor is simply a loadablekernel module... cool! 

•     Being able to insert a module and start new guest
•     provides "low commitment" path to virtualization
•     Provides the /dev/lguest interface, whereby userspace
•      launcher controls and communicates with guest

First write tells us memory size, pagetable, entry point,kernel offset 

A read will run guest until pending signal (-EINTR), or guest does DMA out to launcher  

• The Lguest hypervisor is unique in several ways.
• Host domain is simply a normal kernel in ring-0
• Hypervisor is loaded into top of kernel memory  

Hypervisor contains only core facilities:  

1domain switching code