Re: [PATCH 6/6] powerpc/8xx: implementation of huge pages

Le 14/08/2016 à 16:25, Aneesh Kumar K.V a écrit :

Christophe Leroy [off-list ref] writes:

quoted

The 8xx has 512k and 8M pages. This patch implements hugepages using
those sizes.

On the 8xx, the size of pages is in the PGD entry,
using PS field (bits 28-29):
00 : Small pages (4k or 16k)
01 : 512k pages
10 : reserved
11 : 8M pages

The implementation uses a mix of what is used on BOOKS and BOOKE,
as 512k pages are in HUGEPTE tables while for 8M pages we have
several PGD entries pointing on a leaf HUGEPTE entry

For the time being, we do not support CPU15 ERRATA if HUGETLB is
selected

Can you also document here the format for linux page table with different
huge page size. ?

Euh ... isn't it what I do when explaining the use of the PS field in 
the PGD entry ? That's the thing, that's how the 8xx knows how it is a 
huge page, and that's how Linux will know it is one. On the 8xx, the 
Linux PGD entry (almost) match the L1 MMU entry and the Linux PTE almost 
match the L2 MMU entry (some bits are copied from the PTE to the L1 
entry and then removed from the value writen to the L2 MMU entry)

Christophe

quoted

Signed-off-by: Christophe Leroy <redacted>

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