lguest源码系列之boot.c
[ arch/x86/lguest/boot.c ]
A hypervisor allows multiple Operating Systems to run on a single machine.
* To quote David Wheeler: "Any problem in computer science can be solved with
* another layer of indirection."
*
* We keep things simple in two ways. First, we start with a normal Linux
* kernel and insert a module (lg.ko) which allows us to run other Linux
* kernels the same way we'd run processes. We call the first kernel the Host,
* and the others the Guests. The program which sets up and configures Guests
* (such as the example in Documentation/virtual/lguest/lguest.c) is called the
* Launcher.
*
* Secondly, we only run specially modified Guests, not normal kernels: setting
* CONFIG_LGUEST_GUEST to "y" compiles this file into the kernel so it knows
* how to be a Guest at boot time. This means that you can use the same kernel
* you boot normally (ie. as a Host) as a Guest.
*
* These Guests know that they cannot do privileged operations, such as disable
* interrupts, and that they have to ask the Host to do such things explicitly.
* This file consists of all the replacements for such low-level native
* hardware operations: these special Guest versions call the Host.
*
* So how does the kernel know it's a Guest? We'll see that later, but let's
* just say that we end up here where we replace the native functions various
* "paravirt" structures with our Guest versions, then boot like normal.