i386 : vmalloc size fix

PATCH New Dave Young 1 participant 1 message Jul 29, 2008

Subsystems (3)

Memory management x86 x86 MM

lore

Share & tools

lore

Dave Young

author

2008-07-29 07:53 UTC #0 lore raw

PATCH v2 1/1 i386 : vmalloc size fix

v2 based on the ported version of ingo, changes:
remove unused VMALLOC_RESERVE macro in page_32.h

--
Booting kernel with vmalloc=[any size<=16m] will oops on my pc (i386/1G memory).

BUG_ON in arch/x86/mm/init_32.c triggered:
BUG_ON((unsigned long)high_memory > VMALLOC_START);

It's due to the vm area hole.

In include/asm-x86/pgtable_32.h:
#define VMALLOC_OFFSET (8 * 1024 * 1024)

#define VMALLOC_START	(((unsigned long)high_memory + 2 * VMALLOC_OFFSET - 1) \
			 & ~(VMALLOC_OFFSET - 1))

There's several related point:
1. MAXMEM :
(-__PAGE_OFFSET - __VMALLOC_RESERVE).
The space after VMALLOC_END is included as well, I set it to (VMALLOC_END - PAGE_OFFSET - __VMALLOC_RESERVE)

2. VMALLOC_OFFSET is not considered in __VMALLOC_RESERVE fixed by adding VMALLOC_OFFSET to it.

3. VMALLOC_START :
(((unsigned long)high_memory + 2 * VMALLOC_OFFSET - 1) & ~(VMALLOC_OFFSET - 1))
So it's not always 8M, bigger than 8M possible.
I set it to ((unsigned long)high_memory + VMALLOC_OFFSET)

4. the VMALLOC_RESERVE is an unused macro, so remove it here.

Signed-off-by Dave Young <[email protected]>

arch/x86/mm/pgtable_32.c     |    3 ++-
include/asm-x86/page_32.h    |    3 ---
include/asm-x86/pgtable_32.h |    5 +++--
3 files changed, 5 insertions(+), 6 deletions(-)

arch/x86/mm/pgtable_32.c +2 -1

Index: linux-2.6/arch/x86/mm/pgtable_32.c
===================================================================
@@ -123,7 +123,8 @@
 	if (!arg)
 		return -EINVAL;
 
-	__VMALLOC_RESERVE = memparse(arg, &arg);
+	/* Add VMALLOC_OFFSET to the parsed value due to vm area guard hole*/
+	__VMALLOC_RESERVE = memparse(arg, &arg) + VMALLOC_OFFSET;
 	return 0;
 }
 early_param("vmalloc", parse_vmalloc);

include/asm-x86/page_32.h +0 -3

Index: linux-2.6/include/asm-x86/page_32.h
===================================================================
@@ -89,9 +89,6 @@
 extern unsigned int __VMALLOC_RESERVE;
 extern int sysctl_legacy_va_layout;
 
-#define VMALLOC_RESERVE		((unsigned long)__VMALLOC_RESERVE)
-#define MAXMEM			(-__PAGE_OFFSET - __VMALLOC_RESERVE)
-
 extern void find_low_pfn_range(void);
 extern unsigned long init_memory_mapping(unsigned long start,
 					 unsigned long end);

include/asm-x86/pgtable_32.h +3 -2

Index: linux-2.6/include/asm-x86/pgtable_32.h
===================================================================
@@ -56,8 +56,7 @@
  * area for the same reason. ;)
  */
 #define VMALLOC_OFFSET	(8 * 1024 * 1024)
-#define VMALLOC_START	(((unsigned long)high_memory + 2 * VMALLOC_OFFSET - 1) \
-			 & ~(VMALLOC_OFFSET - 1))
+#define VMALLOC_START	((unsigned long)high_memory + VMALLOC_OFFSET)
 #ifdef CONFIG_X86_PAE
 #define LAST_PKMAP 512
 #else

@@ -73,6 +72,8 @@
 # define VMALLOC_END	(FIXADDR_START - 2 * PAGE_SIZE)
 #endif
 
+#define MAXMEM	(VMALLOC_END - PAGE_OFFSET - __VMALLOC_RESERVE)
+
 /*
  * Define this if things work differently on an i386 and an i486:
  * it will (on an i486) warn about kernel memory accesses that are

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"[email protected]"> [email protected] </a>