Physical memory layout when less than 1 GB is installed
I'm learning linux kernel internals and while reading "Understanding Linux Kernel" there was a couple of questions I can't answer myself. One of them is what is a physical memory layout when I've less than 1 GB memory installed into my system. As I read, kernel maps 0(or 16) MB-896MB phy. RAM into 0xC0000000 linear address and can directly address it. But, does it maps all of the 1 GB phys. memory into kernel space? What about user mode processes in this situation? Where are user mode processes in phys RAM? Or kernel maps only the necessary amount of RAM from 896 MB?
Every article explain only the situation when you've installed 4 GB of memory when kernem maps the 1 GB into kernel space and user processes uses the remaining amount of RAM.
Myabe I misunderstand everything?