diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 91abf5b2fb946c5df74d13249e1fd31cea9bc0bc..41c480ae47dfa881f97f5e3fe6afbf72670b5057 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -139,9 +139,64 @@ void __init e820_print_map(char *who)
  * Sanitize the BIOS e820 map.
  *
  * Some e820 responses include overlapping entries. The following
- * replaces the original e820 map with a new one, removing overlaps.
+ * replaces the original e820 map with a new one, removing overlaps,
+ * and resolving conflicting memory types in favor of highest
+ * numbered type.
  *
+ * The input parameter biosmap points to an array of 'struct
+ * e820entry' which on entry has elements in the range [0, *pnr_map)
+ * valid, and which has space for up to max_nr_map entries.
+ * On return, the resulting sanitized e820 map entries will be in
+ * overwritten in the same location, starting at biosmap.
+ *
+ * The integer pointed to by pnr_map must be valid on entry (the
+ * current number of valid entries located at biosmap) and will
+ * be updated on return, with the new number of valid entries
+ * (something no more than max_nr_map.)
+ *
+ * The return value from sanitize_e820_map() is zero if it
+ * successfully 'sanitized' the map entries passed in, and is -1
+ * if it did nothing, which can happen if either of (1) it was
+ * only passed one map entry, or (2) any of the input map entries
+ * were invalid (start + size < start, meaning that the size was
+ * so big the described memory range wrapped around through zero.)
+ *
+ *	Visually we're performing the following
+ *	(1,2,3,4 = memory types)...
+ *
+ *	Sample memory map (w/overlaps):
+ *	   ____22__________________
+ *	   ______________________4_
+ *	   ____1111________________
+ *	   _44_____________________
+ *	   11111111________________
+ *	   ____________________33__
+ *	   ___________44___________
+ *	   __________33333_________
+ *	   ______________22________
+ *	   ___________________2222_
+ *	   _________111111111______
+ *	   _____________________11_
+ *	   _________________4______
+ *
+ *	Sanitized equivalent (no overlap):
+ *	   1_______________________
+ *	   _44_____________________
+ *	   ___1____________________
+ *	   ____22__________________
+ *	   ______11________________
+ *	   _________1______________
+ *	   __________3_____________
+ *	   ___________44___________
+ *	   _____________33_________
+ *	   _______________2________
+ *	   ________________1_______
+ *	   _________________4______
+ *	   ___________________2____
+ *	   ____________________33__
+ *	   ______________________4_
  */
+
 int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
 				int *pnr_map)
 {
@@ -162,43 +217,6 @@ static struct e820entry new_bios[E820_X_MAX] __initdata;
 	int old_nr, new_nr, chg_nr;
 	int i;
 
-	/*
-		Visually we're performing the following
-		(1,2,3,4 = memory types)...
-
-		Sample memory map (w/overlaps):
-		   ____22__________________
-		   ______________________4_
-		   ____1111________________
-		   _44_____________________
-		   11111111________________
-		   ____________________33__
-		   ___________44___________
-		   __________33333_________
-		   ______________22________
-		   ___________________2222_
-		   _________111111111______
-		   _____________________11_
-		   _________________4______
-
-		Sanitized equivalent (no overlap):
-		   1_______________________
-		   _44_____________________
-		   ___1____________________
-		   ____22__________________
-		   ______11________________
-		   _________1______________
-		   __________3_____________
-		   ___________44___________
-		   _____________33_________
-		   _______________2________
-		   ________________1_______
-		   _________________4______
-		   ___________________2____
-		   ____________________33__
-		   ______________________4_
-	*/
-
 	/* if there's only one memory region, don't bother */
 	if (*pnr_map < 2)
 		return -1;