On Fri, 6 Oct 2006, Vivek Goyal wrote:
On Fri, Oct 06, 2006 at 01:03:50PM -0500, Steve Fox wrote:
On Fri, 2006-10-06 at 18:11 +0100, Mel Gorman wrote:
On (06/10/06 11:36), Vivek Goyal didst pronounce:
Where is bss placed in physical memory? I guess bss_start and bss_stop
from System.map will tell us. That will confirm that above memset step is
stomping over bss. Then we have to just find that somewhere probably
we allocated wrong physical memory area for bootmem allocator map.
BSS is at 0x643000 -> 0x777BC4
init_bootmem wipes from 0x777000 -> 0x8F7000
So the BSS bytes from 0x777000 ->0x777BC4 (which looks very suspiciously
pile a page alignment of addr & PAGE_MASK) gets set to 0xFF. One possible
fix is below. It adds a check in bad_addr() to see if the BSS section is
about to be used for bootmap. It Seems To Work For Me (tm) and illustrates
the source of the problem even if it's not the 100% correct fix.
I was able to boot the machine with Mel's patch applied on top of
-git22.
Please have a look at the attached patch. Does it make some sense.
It makes some sense. As you state, it wastes memory but that is better
than breaking.
Steve, can you please give this patch a try if it fixes the problem?
I boottested the patch on the same machine as Steve was using and it
completed successfully.
Thanks
Vivek
o Currently some code pieces assume that address returned by find_e820_area()
are page aligned. But looks like find_e820_area() had no such intention
and hence one might end up stomping over some of the data. One such
case is bootmem allocator initialization code stomped over bss.
o This patch modified find_e820_area() to return page aligned address. This
might be little wasteful of memory but at the same time probably it is
easier to handle page aligned memory.
Signed-off-by: Vivek Goyal <[email protected]>
---
arch/x86_64/kernel/e820.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff -puN arch/x86_64/kernel/e820.c~x86_64-return-page-aligned-phy-addr-from-find-e820-area arch/x86_64/kernel/e820.c
--- linux-2.6.19-rc1-1M/arch/x86_64/kernel/e820.c~x86_64-return-page-aligned-phy-addr-from-find-e820-area 2006-10-06 15:28:13.000000000 -0400
+++ linux-2.6.19-rc1-1M-root/arch/x86_64/kernel/e820.c 2006-10-06 15:44:45.000000000 -0400
@@ -54,13 +54,13 @@ static inline int bad_addr(unsigned long
/* various gunk below that needed for SMP startup */
if (addr < 0x8000) {
- *addrp = 0x8000;
+ *addrp = PAGE_ALIGN(0x8000);
return 1;
}
/* direct mapping tables of the kernel */
if (last >= table_start<<PAGE_SHIFT && addr < table_end<<PAGE_SHIFT) {
- *addrp = table_end << PAGE_SHIFT;
+ *addrp = PAGE_ALIGN(table_end << PAGE_SHIFT);
return 1;
}
@@ -68,18 +68,18 @@ static inline int bad_addr(unsigned long
#ifdef CONFIG_BLK_DEV_INITRD
if (LOADER_TYPE && INITRD_START && last >= INITRD_START &&
addr < INITRD_START+INITRD_SIZE) {
- *addrp = INITRD_START + INITRD_SIZE;
+ *addrp = PAGE_ALIGN(INITRD_START + INITRD_SIZE);
return 1;
}
#endif
/* kernel code */
- if (last >= __pa_symbol(&_text) && last < __pa_symbol(&_end)) {
- *addrp = __pa_symbol(&_end);
+ if (last >= __pa_symbol(&_text) && addr < __pa_symbol(&_end)) {
+ *addrp = PAGE_ALIGN(__pa_symbol(&_end));
return 1;
}
if (last >= ebda_addr && addr < ebda_addr + ebda_size) {
- *addrp = ebda_addr + ebda_size;
+ *addrp = PAGE_ALIGN(ebda_addr + ebda_size);
return 1;
}
@@ -152,7 +152,7 @@ unsigned long __init find_e820_area(unsi
continue;
while (bad_addr(&addr, size) && addr+size <= ei->addr+ei->size)
;
- last = addr + size;
+ last = PAGE_ALIGN(addr) + size;
if (last > ei->addr + ei->size)
continue;
if (last > end)
_
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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