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powerpc/40x: Limit allocable DRAM during early mapping

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If the size of DRAM is not an exact power of two, we may not have
covered DRAM in its entirety with large 16 and 4 MiB pages.  If that
is the case, we can get non-recoverable page faults when doing the
final PTE mappings for the non-large page PTEs.

Consequently, we restrict the top end of DRAM currently allocable
by updating '__initial_memory_limit_addr' so that calls to the LMB to
allocate PTEs for "tail" coverage with normal-sized pages (or other
reasons) do not attempt to allocate outside the allowed range.

Signed-off-by: Grant Erickson <gerickson@nuovations.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
This commit is contained in:
Grant Erickson 2008-10-29 11:41:14 +00:00 committed by Josh Boyer
parent cb8fdc69a2
commit 5907630ffc
1 changed files with 14 additions and 2 deletions
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16
arch/powerpc/mm/40x_mmu.c
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@ -93,7 +93,7 @@ void __init MMU_init_hw(void)
unsigned long __init mmu_mapin_ram(void)
{
unsigned long v, s;
unsigned long v, s, mapped;
phys_addr_t p;
v = KERNELBASE;
@ -130,5 +130,17 @@ unsigned long __init mmu_mapin_ram(void)
s -= LARGE_PAGE_SIZE_4M;
}
return total_lowmem - s;
mapped = total_lowmem - s;
/* If the size of RAM is not an exact power of two, we may not
* have covered RAM in its entirety with 16 and 4 MiB
* pages. Consequently, restrict the top end of RAM currently
* allocable so that calls to the LMB to allocate PTEs for "tail"
* coverage with normal-sized pages (or other reasons) do not
* attempt to allocate outside the allowed range.
*/
__initial_memory_limit_addr = memstart_addr + mapped;
return mapped;
}