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

[Hariprasad Nellitheertha]

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

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

Signed-off-by: Hariprasad Nellitheertha <hari@xxxxxxxxxx>
---

 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
_