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[S390] dynamic page tables.

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Add support for different number of page table levels dependent
on the highest address used for a process. This will cause a 31 bit
process to use a two level page table instead of the four level page
table that is the default after the pud has been introduced. Likewise
a normal 64 bit process will use three levels instead of four. Only
if a process runs out of the 4 tera bytes which can be addressed with
a three level page table the fourth level is dynamically added. Then
the process can use up to 8 peta byte.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2008-02-09 18:24:37 +01:00
parent 5a216a2083
commit 6252d702c5
13 changed files with 258 additions and 48 deletions
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5
arch/s390/mm/init.c
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@@ -112,8 +112,9 @@ void __init paging_init(void)
init_mm.pgd = swapper_pg_dir;
S390_lowcore.kernel_asce = __pa(init_mm.pgd) & PAGE_MASK;
#ifdef CONFIG_64BIT
S390_lowcore.kernel_asce |= _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
pgd_type = _REGION2_ENTRY_EMPTY;
/* A three level page table (4TB) is enough for the kernel space. */
S390_lowcore.kernel_asce |= _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
pgd_type = _REGION3_ENTRY_EMPTY;
#else
S390_lowcore.kernel_asce |= _ASCE_TABLE_LENGTH;
pgd_type = _SEGMENT_ENTRY_EMPTY;