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