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>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index bee029bb2c7b..b2647974e1a7 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -1,3 +1,16 @@
+/*P:800 Interrupts (traps) are complicated enough to earn their own file.
+ * There are three classes of interrupts:
+ *
+ * 1) Real hardware interrupts which occur while we're running the Guest,
+ * 2) Interrupts for virtual devices attached to the Guest, and
+ * 3) Traps and faults from the Guest.
+ *
+ * Real hardware interrupts must be delivered to the Host, not the Guest.
+ * Virtual interrupts must be delivered to the Guest, but we make them look
+ * just like real hardware would deliver them.  Traps from the Guest can be set
+ * up to go directly back into the Guest, but sometimes the Host wants to see
+ * them first, so we also have a way of "reflecting" them into the Guest as if
+ * they had been delivered to it directly. :*/
 #include <linux/uaccess.h>
 #include "lg.h"