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>

diff --git a/arch/powerpc/mm/hash_low_64.S b/arch/powerpc/mm/hash_low_64.S
index 70f4c83..a719f53 100644 (file)
--- 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 a02266d..8fa07f3 100644 (file)
--- 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 818e2ab..fd2090d 100644 (file)
--- 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 1cbd6b3..c500771 100644 (file)
--- 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 cc6a43b..2e48be8 100644 (file)
--- 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)