lguest: documentation I: Preparation

The netfilter code had very good documentation: the Netfilter Hacking HOWTO.
Noone ever read it.

So this time I'm trying something different, using a bit of Knuthiness.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 62a8133..fc1bf70 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -1,5 +1,10 @@
-/* Simple program to layout "physical" memory for new lguest guest.
- * Linked high to avoid likely physical memory.  */
+/*P:100 This is the Launcher code, a simple program which lays out the
+ * "physical" memory for the new Guest by mapping the kernel image and the
+ * virtual devices, then reads repeatedly from /dev/lguest to run the Guest.
+ *
+ * The only trick: the Makefile links it at a high address so it will be clear
+ * of the guest memory region.  It means that each Guest cannot have more than
+ * about 2.5G of memory on a normally configured Host. :*/
 #define _LARGEFILE64_SOURCE
 #define _GNU_SOURCE
 #include <stdio.h>