powerpc: Free a PTE bit on ppc64 with 64K pages

This frees a PTE bit when using 64K pages on ppc64.  This is done
by getting rid of the separate _PAGE_HASHPTE bit.  Instead, we just test
if any of the 16 sub-page bits is set.  For non-combo pages (ie. real
64K pages), we set SUB0 and the location encoding in that field.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

5 files changed, 31 insertions, 13 deletions

diff --git a/arch/powerpc/mm/hash_low_64.S b/arch/powerpc/mm/hash_low_64.S
index 70f4c833fa32..a719f53921a5 100644
--- a/arch/powerpc/mm/hash_low_64.S
+++ b/arch/powerpc/mm/hash_low_64.S
@@ -388,7 +388,7 @@ _GLOBAL(__hash_page_4K)
          */
         rlwinm  r30,r4,32-9+7,31-7,31-7 /* _PAGE_RW -> _PAGE_DIRTY */
         or      r30,r30,r31
-        ori     r30,r30,_PAGE_BUSY | _PAGE_ACCESSED | _PAGE_HASHPTE
+        ori     r30,r30,_PAGE_BUSY | _PAGE_ACCESSED
         oris    r30,r30,_PAGE_COMBO@h
         /* Write the linux PTE atomically (setting busy) */
         stdcx.  r30,0,r6
@@ -468,7 +468,7 @@ END_FTR_SECTION(CPU_FTR_NOEXECUTE|CPU_FTR_COHERENT_ICACHE, CPU_FTR_NOEXECUTE)
          * go to out-of-line code to try to modify the HPTE. We look for
          * the bit at (1 >> (index + 32))
          */
-        andi.   r0,r31,_PAGE_HASHPTE
+        rldicl. r0,r31,64-12,48
         li      r26,0                   /* Default hidx */
         beq     htab_insert_pte
 
@@ -726,11 +726,11 @@ BEGIN_FTR_SECTION
         bne-    ht64_bail_ok
 END_FTR_SECTION_IFCLR(CPU_FTR_CI_LARGE_PAGE)
         /* Prepare new PTE value (turn access RW into DIRTY, then
-         * add BUSY,HASHPTE and ACCESSED)
+         * add BUSY and ACCESSED)
          */
         rlwinm  r30,r4,32-9+7,31-7,31-7 /* _PAGE_RW -> _PAGE_DIRTY */
         or      r30,r30,r31
-        ori     r30,r30,_PAGE_BUSY | _PAGE_ACCESSED | _PAGE_HASHPTE
+        ori     r30,r30,_PAGE_BUSY | _PAGE_ACCESSED
         /* Write the linux PTE atomically (setting busy) */
         stdcx.  r30,0,r6
         bne-    1b
@@ -798,18 +798,21 @@ END_FTR_SECTION(CPU_FTR_NOEXECUTE|CPU_FTR_COHERENT_ICACHE, CPU_FTR_NOEXECUTE)
         /* Check if we may already be in the hashtable, in this case, we
          * go to out-of-line code to try to modify the HPTE
          */
-        andi.   r0,r31,_PAGE_HASHPTE
+        rldicl. r0,r31,64-12,48
         bne     ht64_modify_pte
 
 ht64_insert_pte:
         /* Clear hpte bits in new pte (we also clear BUSY btw) and
-         * add _PAGE_HASHPTE
+         * add _PAGE_HPTE_SUB0
          */
         lis     r0,_PAGE_HPTEFLAGS@h
         ori     r0,r0,_PAGE_HPTEFLAGS@l
         andc    r30,r30,r0
+#ifdef CONFIG_PPC_64K_PAGES
+        oris    r30,r30,_PAGE_HPTE_SUB0@h
+#else
         ori     r30,r30,_PAGE_HASHPTE
-
+#endif
         /* Phyical address in r5 */
         rldicl  r5,r31,64-PTE_RPN_SHIFT,PTE_RPN_SHIFT
         sldi    r5,r5,PAGE_SHIFT
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index a02266dad215..8fa07f3f6c2b 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -458,8 +458,7 @@ int hash_huge_page(struct mm_struct *mm, unsigned long access,
                 old_pte = pte_val(*ptep);
                 if (old_pte & _PAGE_BUSY)
                         goto out;
-                new_pte = old_pte | _PAGE_BUSY |
-                        _PAGE_ACCESSED | _PAGE_HASHPTE;
+                new_pte = old_pte | _PAGE_BUSY | _PAGE_ACCESSED;
         } while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
                                          old_pte, new_pte));
 
@@ -499,8 +498,11 @@ repeat:
                               HPTES_PER_GROUP) & ~0x7UL;
 
                 /* clear HPTE slot informations in new PTE */
+#ifdef CONFIG_PPC_64K_PAGES
+                new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HPTE_SUB0;
+#else
                 new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;
-
+#endif
                 /* Add in WIMG bits */
                 /* XXX We should store these in the pte */
                 /* --BenH: I think they are ... */
diff --git a/include/asm-powerpc/pgtable-4k.h b/include/asm-powerpc/pgtable-4k.h
index 818e2abc81e2..fd2090dc1dce 100644
--- a/include/asm-powerpc/pgtable-4k.h
+++ b/include/asm-powerpc/pgtable-4k.h
@@ -41,6 +41,7 @@
 #define PGDIR_MASK      (~(PGDIR_SIZE-1))
 
 /* PTE bits */
+#define _PAGE_HASHPTE   0x0400 /* software: pte has an associated HPTE */
 #define _PAGE_SECONDARY 0x8000 /* software: HPTE is in secondary group */
 #define _PAGE_GROUP_IX  0x7000 /* software: HPTE index within group */
 #define _PAGE_F_SECOND  _PAGE_SECONDARY
diff --git a/include/asm-powerpc/pgtable-64k.h b/include/asm-powerpc/pgtable-64k.h
index 1cbd6b377eea..c5007712473f 100644
--- a/include/asm-powerpc/pgtable-64k.h
+++ b/include/asm-powerpc/pgtable-64k.h
@@ -75,6 +75,20 @@ static inline struct subpage_prot_table *pgd_subpage_prot(pgd_t *pgd)
 #define _PAGE_COMBO     0x10000000 /* this is a combo 4k page */
 #define _PAGE_4K_PFN    0x20000000 /* PFN is for a single 4k page */
 
+/* For 64K page, we don't have a separate _PAGE_HASHPTE bit. Instead,
+ * we set that to be the whole sub-bits mask. The C code will only
+ * test this, so a multi-bit mask will work. For combo pages, this
+ * is equivalent as effectively, the old _PAGE_HASHPTE was an OR of
+ * all the sub bits. For real 64k pages, we now have the assembly set
+ * _PAGE_HPTE_SUB0 in addition to setting the HIDX bits which overlap
+ * that mask. This is fine as long as the HIDX bits are never set on
+ * a PTE that isn't hashed, which is the case today.
+ *
+ * A little nit is for the huge page C code, which does the hashing
+ * in C, we need to provide which bit to use.
+ */
+#define _PAGE_HASHPTE   _PAGE_HPTE_SUB
+
 /* Note the full page bits must be in the same location as for normal
  * 4k pages as the same asssembly will be used to insert 64K pages
  * wether the kernel has CONFIG_PPC_64K_PAGES or not
@@ -83,8 +97,7 @@ static inline struct subpage_prot_table *pgd_subpage_prot(pgd_t *pgd)
 #define _PAGE_F_GIX     0x00007000 /* full page: hidx bits */
 
 /* PTE flags to conserve for HPTE identification */
-#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | _PAGE_HPTE_SUB |\
-                         _PAGE_COMBO)
+#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | _PAGE_COMBO)
 
 /* Shift to put page number into pte.
  *
diff --git a/include/asm-powerpc/pgtable-ppc64.h b/include/asm-powerpc/pgtable-ppc64.h
index cc6a43ba41d0..2e48be841cc9 100644
--- a/include/asm-powerpc/pgtable-ppc64.h
+++ b/include/asm-powerpc/pgtable-ppc64.h
@@ -91,7 +91,6 @@
 #define _PAGE_DIRTY     0x0080 /* C: page changed */
 #define _PAGE_ACCESSED  0x0100 /* R: page referenced */
 #define _PAGE_RW        0x0200 /* software: user write access allowed */
-#define _PAGE_HASHPTE   0x0400 /* software: pte has an associated HPTE */
 #define _PAGE_BUSY      0x0800 /* software: PTE & hash are busy */
 
 #define _PAGE_BASE      (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_COHERENT)