David Miller wrote: [Wed Nov 13 2013, 02:18:49AM EST]
>
> To make the page tables compact, we were using 32-bit PGDs and PMDs.
> We only had to support <= 43 bits of physical addresses so this was
> quite feasible.
>
> In order to support larger physical addresses we have to move to
> 64-bit PGDs and PMDs.
>
> Most of the changes are straight-forward:
>
> 1) {pgd,pmd}_t --> unsigned long
>
> 2) Anything that tries to use plain "unsigned int" types with pgd/pmd
> values needs to be adjusted. In particular things like "0U" become
> "0UL".
>
> 3) {PGDIR,PMD}_BITS decrease by one.
>
> 4) In the assembler page table walkers, use "ldxa" instead of "lduwa"
> and adjust the low bit masks to clear out the low 3 bits instead of
> just the low 2 bits during pgd/pmd address formation.
>
> Also, use PTRS_PER_PGD and PTRS_PER_PMD in the sizing of the
> swapper_{pg_dir,low_pmd_dir} arrays.
>
> This patch does not try to take advantage of having 64-bits in the
> PMDs to simplify the hugepage code, that will come in a subsequent
> change.
>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> ---
Acked-by: Bob Picco <bob.picco@xxxxxxxxxx>
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