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powerpc/8xx: Implement pXX_leaf_size() support 

Christophe Leroy wrote:

> I can help with powerpc 8xx. It is a 32 bits powerpc. The PGD has 1024
> entries, that means each entry maps 4M.
>
> Page sizes are 4k, 16k, 512k and 8M.
>
> For the 8M pages we use hugepd with a single entry. The two related PGD
> entries point to the same hugepd.
>
> For the other sizes, they are in standard page tables. 16k pages appear
> 4 times in the page table. 512k entries appear 128 times in the page
> table.
>
> When the PGD entry has _PMD_PAGE_8M bits, the PMD entry points to a
> hugepd with holds the single 8M entry.
>
> In the PTE, we have two bits: _PAGE_SPS and _PAGE_HUGE
>
> _PAGE_HUGE means it is a 512k page
> _PAGE_SPS means it is not a 4k page
>
> The kernel can by build either with 4k pages as standard page size, or
> 16k pages. It doesn't change the page table layout though.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201126121121.364451610@infradead.org
This commit is contained in:
Peter Zijlstra 2020-11-26 11:53:33 +01:00
parent d55863db1d
commit c5eecbb58f
1 changed files with 23 additions and 0 deletions
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23
arch/powerpc/include/asm/nohash/32/pte-8xx.h
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@ -135,6 +135,29 @@ static inline pte_t pte_mkhuge(pte_t pte)
}
#define pte_mkhuge pte_mkhuge
static inline unsigned long pgd_leaf_size(pgd_t pgd)
{
if (pgd_val(pgd) & _PMD_PAGE_8M)
return SZ_8M;
return SZ_4M;
}
#define pgd_leaf_size pgd_leaf_size
static inline unsigned long pte_leaf_size(pte_t pte)
{
pte_basic_t val = pte_val(pte);
if (val & _PAGE_HUGE)
return SZ_512K;
if (val & _PAGE_SPS)
return SZ_16K;
return SZ_4K;
}
#define pte_leaf_size pte_leaf_size
#endif
#endif /* __KERNEL__ */