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SubjectRe: [patch] mm: sparsemem memory_present() memory corruption fix
On Tue, Apr 15, 2008 at 6:02 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * 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.

also 64 bit
early_node_map[10] active PFN ranges
0: 0 -> 149
0: 256 -> 917408
0: 1048576 -> 8519680
1: 8519680 -> 16908288
2: 16908288 -> 25296896
3: 25296896 -> 33685504
4: 33685504 -> 42074112
5: 42074112 -> 50462720
6: 50462720 -> 58851328
7: 58851328 -> 67239936

and 32 bit only has one entry
[ 0.000000] early_node_map[1] active PFN ranges
[ 0.000000] 0: 0 -> 1048576

YH


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