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    SubjectRe: 2.6.16-rc5 huge memory detection regression
    Martin MOKREJ__ <mmokrejs@ribosome.natur.cuni.cz> wrote:
    >
    > ...
    > >
    > >> --- tmp/boot-2.6.15.txt 2006-03-07 11:45:48.015509048 +0100
    > >> +++ tmp/boot-2.6.16-rc5.txt 2006-03-07 11:45:48.029506920 +0100
    > >> @@ -1,4 +1,4 @@
    > >> -Linux version 2.6.15 (root@phylo) (gcc version 3.4.5 (Gentoo 3.4.5-r1, ssp-3.4.5-1.0, pie-8.7.9)) #1 SMP Mon Mar 6 20:20:06 MET 2006
    > >> +Linux version 2.6.16-rc5 (root@phylo) (gcc version 3.4.5 (Gentoo 3.4.5-r1, ssp-3.4.5-1.0, pie-8.7.9)) #1 SMP Mon Mar 6 19:58:24 MET 2006
    > >> BIOS-provided physical RAM map:
    > >> BIOS-e820: 0000000000000000 - 000000000009a800 (usable)
    > >> BIOS-e820: 000000000009a800 - 00000000000a0000 (reserved)
    > >> @@ -12,16 +12,16 @@
    > >> BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
    > >> BIOS-e820: 00000000ff800000 - 00000000ffc00000 (reserved)
    > >> BIOS-e820: 00000000fffffc00 - 0000000100000000 (reserved)
    > >> - BIOS-e820: 0000000100000000 - 0000000430000000 (usable)
    > >> -16256MB HIGHMEM available.
    > >> + BIOS-e820: 0000000100000000 - 0000000230000000 (usable)
    > >> +8064MB HIGHMEM available.
    > >
    > >
    > > These numbers are what the BIOS is telling the kernel about your machine.
    > > Was the BIOS changed?
    >
    > No, it hasn't since we got the motherboard. Yes, it is 1.20 instead
    > of 1.50. The MSI web is such a crap I couldn't first of all get the
    > file at all and once found on a local reseller's page the zip file
    > contains no Changelog, so I have no clue what happened between 1.20
    > and 1.50 BIOS revision.
    >
    > >
    > > If not, you might need to wiggle those DIMMs or something.
    >
    > It is really something else, 16GB can be seen under 2.6.15,
    > 2.6.15-rc1 (if I remember right my previous kernel version).
    > I can reproduce just by booting with "wrong" kernel version.
    > Any other recommendation? Except flashing and praying?
    > I haven't touched the BIOS setting either, I worked completely remotely.
    >

    Are you sure that it was 2.6.15 which found the full 16G?

    Because there was a change which could have affected this. But it was
    merged in late October and was present in 2.6.15.


    You could try a `patch -p1 -R < this:'

    diff-tree f014a556e714dfb02502e3be6146a39ca625f33c (from 750deaa4021da1cf9fdb1e20861a10c76fd7f2bc)
    Author: Dave Hansen <haveblue@us.ibm.com>
    Date: Sun Oct 30 14:59:37 2005 -0800

    [PATCH] fixup bogus e820 entry with mem=

    This was reported because someone was getting oopses reading /proc/iomem.
    It was tracked down to a zero-sized 'struct resource' entry which was
    located right at 4GB.

    You need two conditions to hit this bug: a BIOS E820_RAM area starting at
    exactly the boundary where you specify mem= (to get a zero-sized entry),
    and for the legacy_init_iomem_resources() loop to skip that resource (which
    only happens at exactly 4G).

    I think the killing zero-sized e820 entry is the easiest way to fix this.

    Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

    diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
    index 9b8c8a1..b48ac63 100644
    --- a/arch/i386/kernel/setup.c
    +++ b/arch/i386/kernel/setup.c
    @@ -389,14 +389,24 @@ static void __init limit_regions(unsigne
    }
    }
    for (i = 0; i < e820.nr_map; i++) {
    - if (e820.map[i].type == E820_RAM) {
    - current_addr = e820.map[i].addr + e820.map[i].size;
    - if (current_addr >= size) {
    - e820.map[i].size -= current_addr-size;
    - e820.nr_map = i + 1;
    - return;
    - }
    + current_addr = e820.map[i].addr + e820.map[i].size;
    + if (current_addr < size)
    + continue;
    +
    + if (e820.map[i].type != E820_RAM)
    + continue;
    +
    + if (e820.map[i].addr >= size) {
    + /*
    + * This region starts past the end of the
    + * requested size, skip it completely.
    + */
    + e820.nr_map = i;
    + } else {
    + e820.nr_map = i + 1;
    + e820.map[i].size -= current_addr - size;
    }
    + return;
    }
    }

    -
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