Subject: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed hpte pages.

From: Ram Pai <[email-masked]>
Date: Fri, 16 Jun 2017 20:52:34 -0700

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.

This patch does the following change to 64K PTE that is
backed by 64K hpte.

H_PAGE_F_SECOND which occupied bit 4 moves to the second part
        of the pte.
H_PAGE_F_GIX which  occupied bit 5, 6 and 7 also moves to the
        second part of the pte.

since bit 7 is now freed up, we move H_PAGE_BUSY from bit 9
to bit 7. Trying to minimize gaps so that contiguous bits
can be allocated if needed in the future.

The second part of the PTE will hold
(H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63.

Signed-off-by: Ram Pai <[email-masked]>
---
 arch/powerpc/include/asm/book3s/64/hash-64k.h | 26 ++++++++------------------
 arch/powerpc/mm/hash64_64k.c                  | 16 +++++++---------
 arch/powerpc/mm/hugetlbpage-hash64.c          | 16 ++++++----------
 3 files changed, 21 insertions(+), 37 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 0eb3c89..2fa5c60 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -12,12 +12,8 @@
  */
 #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_F_SECOND	_RPAGE_RSV2	/* HPTE is in 2ndary HPTEG */
-#define H_PAGE_F_GIX	(_RPAGE_RSV3 | _RPAGE_RSV4 | _RPAGE_RPN44)
-#define H_PAGE_F_GIX_SHIFT	56
 
-
-#define H_PAGE_BUSY	_RPAGE_RPN42     /* software: PTE & hash are busy */
+#define H_PAGE_BUSY	_RPAGE_RPN44     /* software: PTE & hash are busy */
 #define H_PAGE_HASHPTE	_RPAGE_RPN43    /* PTE has associated HPTE */
 
 /*
@@ -56,24 +52,18 @@ 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;
-	}
+	/*
+	 * The store side ordering is done in __hash_page_4K
+	 */
+	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);
 }
 
 static inline unsigned long set_hidx_slot(pte_t *ptep, real_pte_t rpte,
diff --git a/arch/powerpc/mm/hash64_64k.c b/arch/powerpc/mm/hash64_64k.c
index 3702a3c..1c25ec2 100644
--- a/arch/powerpc/mm/hash64_64k.c
+++ b/arch/powerpc/mm/hash64_64k.c
@@ -211,6 +211,7 @@ 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 hpte_group;
 	unsigned long rflags, pa;
 	unsigned long old_pte, new_pte;
@@ -247,6 +248,7 @@ 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))
@@ -254,16 +256,13 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
 
 	vpn  = hpt_vpn(ea, vsid, ssize);
 	if (unlikely(old_pte & H_PAGE_HASHPTE)) {
+		unsigned long gslot;
+
 		/*
 		 * There MIGHT be an HPTE for this pte
 		 */
-		hash = hpt_hash(vpn, shift, ssize);
-		if (old_pte & H_PAGE_F_SECOND)
-			hash = ~hash;
-		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
-		slot += (old_pte & H_PAGE_F_GIX) >> H_PAGE_F_GIX_SHIFT;
-
-		if (mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, MMU_PAGE_64K,
+		gslot = get_hidx_gslot(vpn, shift, ssize, rpte, 0);
+		if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_64K,
 					       MMU_PAGE_64K, ssize,
 					       flags) == -1)
 			old_pte &= ~_PAGE_HPTEFLAGS;
@@ -313,8 +312,7 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
 			return -1;
 		}
 
-		new_pte |= (slot << H_PAGE_F_GIX_SHIFT) &
-				(H_PAGE_F_SECOND | H_PAGE_F_GIX);
+		set_hidx_slot(ptep, rpte, 0, slot);
 		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
 	}
 	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index a84bb44..239ca86 100644
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -22,6 +22,7 @@ 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 vpn;
 	unsigned long old_pte, new_pte;
 	unsigned long rflags, pa, sz;
@@ -61,6 +62,7 @@ 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))
@@ -71,15 +73,10 @@ 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 gslot;
 
-		hash = hpt_hash(vpn, shift, ssize);
-		if (old_pte & H_PAGE_F_SECOND)
-			hash = ~hash;
-		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
-		slot += (old_pte & H_PAGE_F_GIX) >> H_PAGE_F_GIX_SHIFT;
-
-		if (mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, mmu_psize,
+		gslot = get_hidx_gslot(vpn, shift, ssize, rpte, 0);
+		if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, mmu_psize,
 					       mmu_psize, ssize, flags) == -1)
 			old_pte &= ~_PAGE_HPTEFLAGS;
 	}
@@ -106,8 +103,7 @@ 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);
+		new_pte |= set_hidx_slot(ptep, rpte, 0, slot);
 	}
 
 	/*
-- 
1.8.3.1