[PATCH 02/35] x86: Handle multiple exactmaps and out of order exactmap

[Yinghai Lu <yinghai@kernel.org>]

Current code expect that we only have one exactmap and exactmap need to
first one in memmap=.

memmap=exactmap will throw away all original entries, but also until
then user defined (through other provided memmap= parameters) areas.
That means all memmap= boot parameters passed before a memmap=exactmap
parameter are not recognized.

Without this fix:
	memmap=x@y memmap=exactmap memmap=i#k
only i#k would get recognized.  This is wrong.

This fix will scan the boot_command_line to find if there is exactmap at
first and only throw away all original e820 entries once, and then parse
other memmap= option.

-v2: incorporate change log from Thomas Renninger.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Reviewed-by: Thomas Renninger <trenn@suse.de>
---
 arch/x86/kernel/e820.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index d32abea..dc0b9f0 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -835,6 +835,8 @@ static int __init parse_memopt(char *p)
 }
 early_param("mem", parse_memopt);
 
+static bool __initdata exactmap_parsed;
+
 static int __init parse_memmap_one(char *p)
 {
 	char *oldp;
@@ -844,6 +846,10 @@ static int __init parse_memmap_one(char *p)
 		return -EINVAL;
 
 	if (!strncmp(p, "exactmap", 8)) {
+		if (exactmap_parsed)
+			return 0;
+
+		exactmap_parsed = true;
 #ifdef CONFIG_CRASH_DUMP
 		/*
 		 * If we are doing a crash dump, we still need to know
@@ -879,6 +885,12 @@ static int __init parse_memmap_one(char *p)
 }
 static int __init parse_memmap_opt(char *str)
 {
+	char *p = boot_command_line;
+
+	p = strstr(p, "exactmap");
+	if (p)
+		parse_memmap_one("exactmap");
+
 	while (str) {
 		char *k = strchr(str, ',');
 
-- 
1.7.10.4