[RFC][x86_64] Introducing the memmap= kernel command line option

[Hariprasad Nellitheertha <hari@in.ibm.com>]

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Hi Andi,

In order to port kdump to x86_64, we need to have the 
memmap= kernel command line option available. This is so 
that the dump-capture kernel can be booted with a custom 
memory map.

The attached patch adds the memmap= functionality to the 
x86_64 kernel. It is against 2.6.12-rc2-mm3. I have done 
some amount of testing and it is working fine.

Could you kindly review this patch and let me know your 
thoughts on it.

Thanks and Regards,
Hari

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This patch adds the 'memmap=' kernel command line option for the
x86_64 kernel.

Signed-off-by: Hariprasad Nellitheertha <hari@in.ibm.com>
---

 linux-2.6.12-rc2-hari/Documentation/kernel-parameters.txt |    2 -
 linux-2.6.12-rc2-hari/arch/x86_64/kernel/e820.c           |   25 ++++++++++++++
 linux-2.6.12-rc2-hari/arch/x86_64/kernel/setup.c          |    3 +
 linux-2.6.12-rc2-hari/include/asm-x86_64/e820.h           |    2 +
 4 files changed, 31 insertions(+), 1 deletion(-)

diff -puN arch/x86_64/kernel/e820.c~x8664-memmap-command-line-option arch/x86_64/kernel/e820.c
--- linux-2.6.12-rc2/arch/x86_64/kernel/e820.c~x8664-memmap-command-line-option	2005-04-15 10:15:04.000000000 +0530
+++ linux-2.6.12-rc2-hari/arch/x86_64/kernel/e820.c	2005-04-15 10:17:23.000000000 +0530
@@ -513,6 +513,31 @@ void __init parse_memopt(char *p, char *
 	end_user_pfn >>= PAGE_SHIFT;	
 } 
 
+void __init parse_memmapopt(char *p, char **from)
+{
+	if (!memcmp(p, "exactmap", 8)) {
+		p += 8;
+		e820.nr_map = 0;
+	} else {
+		unsigned long long start_at, mem_size;
+
+		mem_size = memparse(p, from);
+		p = *from;
+		if (*p == '@') {
+			start_at = memparse(p+1, from);
+			add_memory_region(start_at, mem_size, E820_RAM);
+		} else if (*p == '#') {
+			start_at = memparse(p+1, from);
+			add_memory_region(start_at, mem_size, E820_ACPI);
+		} else if (*p == '$') {
+			start_at = memparse(p+1, from);
+			add_memory_region(start_at, mem_size, E820_RESERVED);
+		} else {
+			end_user_pfn = (mem_size >> PAGE_SHIFT);
+		}
+	}
+}
+
 unsigned long pci_mem_start = 0xaeedbabe;
 
 /*
diff -puN arch/x86_64/kernel/setup.c~x8664-memmap-command-line-option arch/x86_64/kernel/setup.c
--- linux-2.6.12-rc2/arch/x86_64/kernel/setup.c~x8664-memmap-command-line-option	2005-04-15 10:15:04.000000000 +0530
+++ linux-2.6.12-rc2-hari/arch/x86_64/kernel/setup.c	2005-04-15 10:15:04.000000000 +0530
@@ -349,6 +349,9 @@ static __init void parse_cmdline_early (
 		if (!memcmp(from, "mem=", 4))
 			parse_memopt(from+4, &from); 
 
+		if (!memcmp(from, "memmap=", 7))
+			parse_memmapopt(from+7, &from);
+
 #ifdef CONFIG_DISCONTIGMEM
 		if (!memcmp(from, "numa=", 5))
 			numa_setup(from+5); 
diff -puN include/asm-x86_64/e820.h~x8664-memmap-command-line-option include/asm-x86_64/e820.h
--- linux-2.6.12-rc2/include/asm-x86_64/e820.h~x8664-memmap-command-line-option	2005-04-15 10:15:04.000000000 +0530
+++ linux-2.6.12-rc2-hari/include/asm-x86_64/e820.h	2005-04-15 10:15:04.000000000 +0530
@@ -54,6 +54,8 @@ extern void e820_setup_gap(void);
 
 extern void __init parse_memopt(char *p, char **end);
 
+extern void __init parse_memmapopt(char *p, char **end);
+
 extern struct e820map e820;
 #endif/*!__ASSEMBLY__*/
 
diff -puN Documentation/kernel-parameters.txt~x8664-memmap-command-line-option Documentation/kernel-parameters.txt
--- linux-2.6.12-rc2/Documentation/kernel-parameters.txt~x8664-memmap-command-line-option	2005-04-15 10:19:37.000000000 +0530
+++ linux-2.6.12-rc2-hari/Documentation/kernel-parameters.txt	2005-04-15 10:19:56.000000000 +0530
@@ -794,7 +794,7 @@ running once the system is up.
 	mem=nopentium	[BUGS=IA-32] Disable usage of 4MB pages for kernel
 			memory.
 
-	memmap=exactmap	[KNL,IA-32] Enable setting of an exact
+	memmap=exactmap	[KNL,IA-32,X86-64] Enable setting of an exact
 			E820 memory map, as specified by the user.
 			Such memmap=exactmap lines can be constructed based on
 			BIOS output or other requirements. See the memmap=nn@ss
_