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    SubjectRe: 2.6.18-mm2 boot failure on x86-64
    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.

    Steve, can you please give this patch a try if it fixes the problem?

    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 <vgoyal@in.ibm.com>
    ---

    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)
    _
    -
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