Ram Pai [off-list ref] writes:

Rearrange 64K PTE bits to  free  up  bits 3, 4, 5  and  6
in the 64K backed HPTE pages. This along with the earlier
patch will  entirely free  up the four bits from 64K PTE.
The bit numbers are  big-endian as defined in the  ISA3.0

This patch  does  the  following change to 64K PTE backed
by 64K HPTE.

H_PAGE_F_SECOND (S) which  occupied  bit  4  moves to the
	second part of the pte to bit 60.
H_PAGE_F_GIX (G,I,X) which  occupied  bit 5, 6 and 7 also
	moves  to  the   second part of the pte to bit 61,
       	62, 63, 64 respectively

since bit 7 is now freed up, we move H_PAGE_BUSY (B) from
bit  9  to  bit  7.

The second part of the PTE will hold
(H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63.
NOTE: None of the bits in the secondary PTE were not used
by 64k-HPTE backed PTE.

Before the patch, the 64K HPTE backed 64k PTE format was
as follows

 0 1 2 3 4  5  6  7  8 9 10...........................63
 : : : : :  :  :  :  : : :                            :
 v v v v v  v  v  v  v v v                            v

,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-,
|x|x|x| |S |G |I |X |x|B| |x|x|................|x|x|x|x| <- primary pte
'_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_'
| | | | |  |  |  |  | | | | |..................| | | | | <- secondary pte
'_'_'_'_'__'__'__'__'_'_'_'_'__________________'_'_'_'_'

After the patch, the 64k HPTE backed 64k PTE format is
as follows

 0 1 2 3 4  5  6  7  8 9 10...........................63
 : : : : :  :  :  :  : : :                            :
 v v v v v  v  v  v  v v v                            v

,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-,
|x|x|x| |  |  |  |B |x| | |x|x|................|.|.|.|.| <- primary pte
'_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_'
| | | | |  |  |  |  | | | | |..................|S|G|I|X| <- secondary pte
'_'_'_'_'__'__'__'__'_'_'_'_'__________________'_'_'_'_'

The above PTE changes is applicable to hugetlbpages aswell.

The patch does the following code changes:

a) moves  the  H_PAGE_F_SECOND and  H_PAGE_F_GIX to 4k PTE
	header   since it is no more needed b the 64k PTEs.
b) abstracts  out __real_pte() and __rpte_to_hidx() so the
	caller  need not know the bit location of the slot.
c) moves the slot bits the secondary pte.

Reviewed-by: Aneesh Kumar K.V <redacted>
With changes suggested for the first patch.

Signed-off-by: Ram Pai <redacted>
---

-aneesh