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Subject[RFC v6 02/62] powerpc: Free up four 64K PTE bits in 64K backed HPTE pages
Date
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.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
arch/powerpc/include/asm/book3s/64/hash-4k.h | 3 ++
arch/powerpc/include/asm/book3s/64/hash-64k.h | 29 ++++++++++-------------
arch/powerpc/include/asm/book3s/64/hash.h | 3 --
arch/powerpc/mm/hash64_64k.c | 30 ++++++++++++++++++------
arch/powerpc/mm/hugetlbpage-hash64.c | 22 ++++++++++++++----
5 files changed, 55 insertions(+), 32 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash-4k.h b/arch/powerpc/include/asm/book3s/64/hash-4k.h
index f959c00..d2cf949 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-4k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-4k.h
@@ -16,6 +16,9 @@
#define H_PUD_TABLE_SIZE (sizeof(pud_t) << H_PUD_INDEX_SIZE)
#define H_PGD_TABLE_SIZE (sizeof(pgd_t) << H_PGD_INDEX_SIZE)

+#define H_PAGE_F_GIX_SHIFT 56
+#define H_PAGE_F_SECOND _RPAGE_RSV2 /* HPTE is in 2ndary HPTEG */
+#define H_PAGE_F_GIX (_RPAGE_RSV3 | _RPAGE_RSV4 | _RPAGE_RPN44)
#define H_PAGE_BUSY _RPAGE_RSV1 /* software: PTE & hash are busy */

/* PTE flags to conserve for HPTE identification */
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 62e580c..c281f18 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -12,7 +12,7 @@
*/
#define H_PAGE_COMBO _RPAGE_RPN0 /* this is a combo 4k page */
#define H_PAGE_4K_PFN _RPAGE_RPN1 /* PFN is for a single 4k page */
-#define H_PAGE_BUSY _RPAGE_RPN42 /* software: PTE & hash are busy */
+#define H_PAGE_BUSY _RPAGE_RPN44 /* software: PTE & hash are busy */

/*
* We need to differentiate between explicit huge page and THP huge
@@ -21,8 +21,7 @@
#define H_PAGE_THP_HUGE H_PAGE_4K_PFN

/* PTE flags to conserve for HPTE identification */
-#define _PAGE_HPTEFLAGS (H_PAGE_BUSY | H_PAGE_F_SECOND | \
- H_PAGE_F_GIX | H_PAGE_HASHPTE | H_PAGE_COMBO)
+#define _PAGE_HPTEFLAGS (H_PAGE_BUSY | H_PAGE_HASHPTE | H_PAGE_COMBO)
/*
* we support 16 fragments per PTE page of 64K size.
*/
@@ -50,24 +49,22 @@ static inline real_pte_t __real_pte(pte_t pte, pte_t *ptep)
unsigned long *hidxp;

rpte.pte = pte;
- rpte.hidx = 0;
- if (pte_val(pte) & H_PAGE_COMBO) {
- /*
- * Make sure we order the hidx load against the H_PAGE_COMBO
- * check. The store side ordering is done in __hash_page_4K
- */
- smp_rmb();
- hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
- rpte.hidx = *hidxp;
- }
+ /*
+ * Ensure that we do not read the hidx before we read
+ * the pte. Because the writer side is expected
+ * to finish writing the hidx first followed by the pte,
+ * by using smp_wmb().
+ * pte_set_hash_slot() ensures that.
+ */
+ smp_rmb();
+ hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
+ rpte.hidx = *hidxp;
return rpte;
}

static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
{
- if ((pte_val(rpte.pte) & H_PAGE_COMBO))
- return (rpte.hidx >> (index<<2)) & 0xf;
- return (pte_val(rpte.pte) >> H_PAGE_F_GIX_SHIFT) & 0xf;
+ return ((rpte.hidx >> (index<<2)) & 0xfUL);
}

#define __rpte_to_pte(r) ((r).pte)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 2d72964..d27f885 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -8,9 +8,6 @@
*
*/
#define H_PTE_NONE_MASK _PAGE_HPTEFLAGS
-#define H_PAGE_F_GIX_SHIFT 56
-#define H_PAGE_F_SECOND _RPAGE_RSV2 /* HPTE is in 2ndary HPTEG */
-#define H_PAGE_F_GIX (_RPAGE_RSV3 | _RPAGE_RSV4 | _RPAGE_RPN44)
#define H_PAGE_HASHPTE _RPAGE_RPN43 /* PTE has associated HPTE */

#ifdef CONFIG_PPC_64K_PAGES
diff --git a/arch/powerpc/mm/hash64_64k.c b/arch/powerpc/mm/hash64_64k.c
index e573bd3..0012618 100644
--- a/arch/powerpc/mm/hash64_64k.c
+++ b/arch/powerpc/mm/hash64_64k.c
@@ -243,6 +243,8 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
unsigned long vsid, pte_t *ptep, unsigned long trap,
unsigned long flags, int ssize)
{
+ real_pte_t rpte;
+ unsigned long *hidxp;
unsigned long hpte_group;
unsigned long rflags, pa;
unsigned long old_pte, new_pte;
@@ -279,6 +281,7 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
} while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));

rflags = htab_convert_pte_flags(new_pte);
+ rpte = __real_pte(__pte(old_pte), ptep);

if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
@@ -286,15 +289,17 @@ int __hash_page_64K(unsigned long ea, unsigned long access,

vpn = hpt_vpn(ea, vsid, ssize);
if (unlikely(old_pte & H_PAGE_HASHPTE)) {
- /*
- * There MIGHT be an HPTE for this pte
- */
+ unsigned long hash, slot, hidx;
+
hash = hpt_hash(vpn, shift, ssize);
- if (old_pte & H_PAGE_F_SECOND)
+ hidx = __rpte_to_hidx(rpte, 0);
+ if (hidx & _PTEIDX_SECONDARY)
hash = ~hash;
slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
- slot += (old_pte & H_PAGE_F_GIX) >> H_PAGE_F_GIX_SHIFT;
-
+ slot += hidx & _PTEIDX_GROUP_IX;
+ /*
+ * There MIGHT be an HPTE for this pte
+ */
if (mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, MMU_PAGE_64K,
MMU_PAGE_64K, ssize,
flags) == -1)
@@ -344,9 +349,18 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
MMU_PAGE_64K, MMU_PAGE_64K, old_pte);
return -1;
}
+
+ /*
+ * Insert slot number & secondary bit in PTE second half.
+ */
+ hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
+ rpte.hidx &= ~(0xfUL);
+ *hidxp = rpte.hidx | (slot & 0xfUL);
+ /*
+ * check __real_pte for details on matching smp_rmb()
+ */
+ smp_wmb();
new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
- new_pte |= (slot << H_PAGE_F_GIX_SHIFT) &
- (H_PAGE_F_SECOND | H_PAGE_F_GIX);
}
*ptep = __pte(new_pte & ~H_PAGE_BUSY);
return 0;
diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index a84bb44..6f7aee3 100644
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -22,6 +22,8 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
pte_t *ptep, unsigned long trap, unsigned long flags,
int ssize, unsigned int shift, unsigned int mmu_psize)
{
+ real_pte_t rpte;
+ unsigned long *hidxp;
unsigned long vpn;
unsigned long old_pte, new_pte;
unsigned long rflags, pa, sz;
@@ -61,6 +63,7 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
} while(!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));

rflags = htab_convert_pte_flags(new_pte);
+ rpte = __real_pte(__pte(old_pte), ptep);

sz = ((1UL) << shift);
if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
@@ -71,13 +74,14 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
/* Check if pte already has an hpte (case 2) */
if (unlikely(old_pte & H_PAGE_HASHPTE)) {
/* There MIGHT be an HPTE for this pte */
- unsigned long hash, slot;
+ unsigned long hash, slot, hidx;

hash = hpt_hash(vpn, shift, ssize);
- if (old_pte & H_PAGE_F_SECOND)
+ hidx = __rpte_to_hidx(rpte, 0);
+ if (hidx & _PTEIDX_SECONDARY)
hash = ~hash;
slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
- slot += (old_pte & H_PAGE_F_GIX) >> H_PAGE_F_GIX_SHIFT;
+ slot += hidx & _PTEIDX_GROUP_IX;

if (mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, mmu_psize,
mmu_psize, ssize, flags) == -1)
@@ -106,8 +110,16 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
return -1;
}

- new_pte |= (slot << H_PAGE_F_GIX_SHIFT) &
- (H_PAGE_F_SECOND | H_PAGE_F_GIX);
+ /*
+ * Insert slot number & secondary bit in PTE second half.
+ */
+ hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
+ rpte.hidx &= ~(0xfUL);
+ *hidxp = rpte.hidx | (slot & 0xfUL);
+ /*
+ * check __real_pte for details on matching smp_rmb()
+ */
+ smp_wmb();
}

/*
--
1.7.1
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