[PATCH 0/7] powerpc: Free up RPAGE_RSV bits

Ram Pai linuxram at us.ibm.com
Mon Jul 31 10:11:09 AEST 2017

RPAGE_RSV0..4 pte bits are currently used for hpte slot
tracking. We  need  these bits   for  memory-protection
keys. Luckily these  four bits   are  relatively easier 
to move among all the other candidate bits.

For  64K   linux-ptes   backed  by 4k hptes, these bits
are   used for tracking the  validity of the slot value
stored   in the second-part-of-the-pte. We device a new
mechanism for  tracking   the   validity  without using
those bits. The    mechanism  is explained in the first

For 64K  linux-pte  backed by 64K hptes, we simply move
the   slot  tracking bits to the second-part-of-the-pte.

The above  mechanism  is also used to free the bits for
hugetlb linux-ptes.

For 4k linux-pte, we  have only 3 free  bits  available.
We swizzle around the bits and release RPAGE_RSV{2,3,4}
for memory protection keys.

has survived  kernel  compilation on multiple platforms
p8 powernv hash-mode, p9 powernv hash-mode,  p7 powervm,
p8-powervm, p8-kvm-guest.

Has survived git-bisect on p8  power-nv  with  64K page
and 4K page.

This patchset  is  a  spin-off from the memkey patchset.

version v8:
	(1) an  additional  patch   added  to  free  up
             RSV{2,3,4} on 4K linux-pte.

version v7:
	(1) GIX bit reset change  moved  to  the second
		patch  -- noticed by Aneesh.
	(2) Separated this patches from memkey patchset
	(3) merged a  bunch  of  patches, that used the
       		helper function, into one.
version v6:
	(1) No changes related to pte.

version v5:
	(1) No changes related to pte.

version v4:
	(1) No changes related to pte.

version v3:
	(1) split the patches into smaller consumable
	(2) A bug fix while  invalidating a hpte slot
		in __hash_page_4K()
       		-- noticed by Aneesh

version v2:
 	(1) fixed a  bug  in 4k  hpte  backed 64k pte
       		where  page    invalidation   was not
		done  correctly,  and  initialization
	       	of    second-part-of-the-pte  was not
		done    correctly  if the pte was not
	       	yet Hashed with a hpte.
	       	   --	Reported by Aneesh.

version v1: Initial version

Ram Pai (7):
  powerpc: Free up four 64K PTE bits in 4K backed HPTE pages
  powerpc: Free up four 64K PTE bits in 64K backed HPTE pages
  powerpc: Swizzle around 4K PTE bits to free up bit 5 and bit 6
  powerpc: capture the PTE format changes in the dump pte report
  powerpc: introduce pte_set_hash_slot() helper
  powerpc: introduce pte_get_hash_gslot() helper
  powerpc: use helper functions to get and set hash slots

 arch/powerpc/include/asm/book3s/64/hash-4k.h  |   21 ++++
 arch/powerpc/include/asm/book3s/64/hash-64k.h |   61 ++++++++----
 arch/powerpc/include/asm/book3s/64/hash.h     |    8 +-
 arch/powerpc/mm/dump_linuxpagetables.c        |    3 +-
 arch/powerpc/mm/hash64_4k.c                   |   14 +--
 arch/powerpc/mm/hash64_64k.c                  |  124 +++++++++++++------------
 arch/powerpc/mm/hash_utils_64.c               |   35 +++++--
 arch/powerpc/mm/hugetlbpage-hash64.c          |   16 +--
 8 files changed, 167 insertions(+), 115 deletions(-)

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