---
 arch/x86/kernel/e820.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/kernel/e820.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/e820.c
+++ linux-2.6/arch/x86/kernel/e820.c
@@ -845,7 +845,7 @@ static int __init parse_memmap_one(char
 	if (!p)
 		return -EINVAL;
 
-	if (!strncmp(p, "exactmap", 8)) {
+	if (!strncmp(p, "exactmap", 8) || !strncmp(p, "resetusablemap", 14)) {
 		if (exactmap_parsed)
 			return 0;
 
@@ -858,7 +858,11 @@ static int __init parse_memmap_one(char
 		 */
 		saved_max_pfn = e820_end_of_ram_pfn();
 #endif
-		e820.nr_map = 0;
+		if (!strncmp(p, "resetusablemap", 14)) {
+			/* remove all old E820_RAM ranges */
+			e820_remove_range(0, ULLONG_MAX, E820_RAM, 1);
+		} else
+			e820.nr_map = 0;
 		userdef = 1;
 		return 0;
 	}
@@ -890,6 +894,11 @@ static int __init parse_memmap_opt(char
 	p = strstr(p, "exactmap");
 	if (p)
 		parse_memmap_one("exactmap");
+	else {
+		p = strstr(boot_command_line, "resetusablemap");
+		if (p)
+			parse_memmap_one("resetusablemap");
+	}
 
 	while (str) {
 		char *k = strchr(str, ',');