[PATCH 1/2 v2] x86: add max_addr boot option

Wen Congyang
2012-06-11T08:40:35Z

Currently, the boot option max_addr is only supported on ia64 platform.
We also need it on x86 platform.
For example:
There are two nodes:
NODE#0 address range 0x00000000 00000000 - 0x00010000 00000000
NODE#1 address range 0x00010000 00000000 - 0x00020000 00000000
If we only want to use node0, we can specify the max_addr. The boot
option "mem=" can do the same thing now. But the boot option "mem="
means the total memory used by the system. If we tell the user
that the boot option "mem=" can do this, it will confuse the user.
So we need an new boot option "max_addr" on x86 platform.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
Documentation/kernel-parameters.txt | 2 +-
arch/x86/kernel/e820.c | 36 +++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+), 1 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a92c5eb..034609d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1441,7 +1441,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
yeeloong laptop.
Example: machtype=lemote-yeeloong-2f-7inch

- max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
+ max_addr=nn[KMG] [KNL,BOOT,ia64,X86] All physical memory greater
than or equal to this physical address is ignored.

maxcpus= [SMP] Maximum number of processors that an SMP kernel
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 4185797..cd07226 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -47,6 +47,7 @@ unsigned long pci_mem_start = 0xaeedbabe;
#ifdef CONFIG_PCI
EXPORT_SYMBOL(pci_mem_start);
#endif
+static u64 max_addr = ~0ULL;

/*
* This function checks if any part of the range <start,end> is mapped
@@ -119,6 +120,20 @@ static void __init __e820_add_region(struct e820map *e820x, u64 start, u64 size,
return;
}

+ if (start >= max_addr) {
+ printk(KERN_ERR "e820: ignoring [mem %#010llx-%#010llx]\n",
+ (unsigned long long)start,
+ (unsigned long long)(start + size - 1));
+ return;
+ }
+
+ if (max_addr - start < size) {
+ printk(KERN_ERR "e820: ignoring [mem %#010llx-%#010llx]\n",
+ (unsigned long long)max_addr,
+ (unsigned long long)(start + size - 1));
+ size = max_addr - start;
+ }
+
e820x->map[x].addr = start;
e820x->map[x].size = size;
e820x->map[x].type = type;
@@ -835,6 +850,22 @@ static int __init parse_memopt(char *p)
}
early_param("mem", parse_memopt);

+static int __init parse_memmax_opt(char *p)
+{
+ char *oldp;
+
+ if (!p)
+ return -EINVAL;
+
+ oldp = p;
+ max_addr = memparse(p, &p);
+ if (p == oldp)
+ return -EINVAL;
+
+ return 0;
+}
+early_param("max_addr", parse_memmax_opt);
+
static int __init parse_memmap_opt(char *p)
{
char *oldp;
@@ -881,6 +912,11 @@ early_param("memmap", parse_memmap_opt);

void __init finish_e820_parsing(void)
{
+ if (max_addr != ~0ULL) {
+ userdef = 1;
+ e820_remove_range(max_addr, ULLONG_MAX - max_addr, E820_RAM, 1);
+ }
+
if (userdef) {
u32 nr = e820.nr_map;

--
1.7.1