lkml.org 
[lkml]   [2008]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch] mm: sparsemem memory_present() memory corruption fix

    * Yinghai Lu <yhlu.kernel@gmail.com> wrote:

    > On Tue, Apr 15, 2008 at 5:44 PM, Ingo Molnar <mingo@elte.hu> wrote:
    > >
    > > * Yinghai Lu <yhlu.kernel@gmail.com> wrote:
    > >
    > > > > + unsigned long max_arch_pfn = 1ULL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);
    > > > >
    > > > > and also check my analysis whether it is correct and whether it
    > > > > matches the reported bug patterns. But otherwise the fix looks like
    > > > > a safe fix for v2.6.25-final to me - it only filters out values
    > > > > from sparsemem input that are nonsensical in the sparsemem
    > > > > framework anyway.
    > > >
    > >
    > > > can you check why find_max_pfn() e820_32.c need to call
    > > > memory_present? wonder if it can be removed.
    > >
    > > this is the only call to memory_present() we do in 32-bit arch setup, so
    > > it's required.
    > >
    > > (the function find_max_pfn() is woefully misnamed, but that's a cleanup
    > > - i just fixed this in x86.git.)
    >
    > 64 bit is calling that via paging_init
    > ==>sparse_memory_present_with_active_regions(MAX_NUMNODES).
    >
    > and
    > void __init sparse_memory_present_with_active_regions(int nid)

    yeah - 64-bit is different here and it's not affected by the problem
    because there SECTION_SIZE_BITS is 27 (==128 MB chunks),
    MAX_PHYSADDR_BITS is 40 (== 1 TB) - giving 8192 section map entries.
    Once larger than 1 TB 64-bit x86 systems are created MAX_PHYSADDR_BITS
    needs to be increased.

    The only downside of the current setup on 64-bit is that it wastes 128K
    of RAM on the majority of systems. We could perhaps try a shift of 28,
    which halves the footprint to 64K of RAM, and which still is good enough
    to allow the PCI aperture to remain a hole on most systems. It would
    also compress the data-cache footprint of the sparse memory maps.
    (without having to use sparsemem-extreme indirection)

    Ingo


    \
     
     \ /
      Last update: 2008-04-16 03:05    [W:0.031 / U:3.352 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site