[PATCH] ppc64: support 64k pages

Adds a new CONFIG_PPC_64K_PAGES which, when enabled, changes the kernel
base page size to 64K.  The resulting kernel still boots on any
hardware.  On current machines with 4K pages support only, the kernel
will maintain 16 "subpages" for each 64K page transparently.

Note that while real 64K capable HW has been tested, the current patch
will not enable it yet as such hardware is not released yet, and I'm
still verifying with the firmware architects the proper to get the
information from the newer hypervisors.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 88 insertions, 0 deletions

diff --git a/include/asm-ppc64/pgtable-4k.h b/include/asm-ppc64/pgtable-4k.h
new file mode 100644
index 000000000000..c883a2748558
--- /dev/null
+++ b/include/asm-ppc64/pgtable-4k.h
@@ -0,0 +1,88 @@
+/*
+ * Entries per page directory level.  The PTE level must use a 64b record
+ * for each page table entry.  The PMD and PGD level use a 32b record for
+ * each entry by assuming that each entry is page aligned.
+ */
+#define PTE_INDEX_SIZE  9
+#define PMD_INDEX_SIZE  7
+#define PUD_INDEX_SIZE  7
+#define PGD_INDEX_SIZE  9
+
+#define PTE_TABLE_SIZE  (sizeof(pte_t) << PTE_INDEX_SIZE)
+#define PMD_TABLE_SIZE  (sizeof(pmd_t) << PMD_INDEX_SIZE)
+#define PUD_TABLE_SIZE  (sizeof(pud_t) << PUD_INDEX_SIZE)
+#define PGD_TABLE_SIZE  (sizeof(pgd_t) << PGD_INDEX_SIZE)
+
+#define PTRS_PER_PTE    (1 << PTE_INDEX_SIZE)
+#define PTRS_PER_PMD    (1 << PMD_INDEX_SIZE)
+#define PTRS_PER_PUD    (1 << PMD_INDEX_SIZE)
+#define PTRS_PER_PGD    (1 << PGD_INDEX_SIZE)
+
+/* PMD_SHIFT determines what a second-level page table entry can map */
+#define PMD_SHIFT       (PAGE_SHIFT + PTE_INDEX_SIZE)
+#define PMD_SIZE        (1UL << PMD_SHIFT)
+#define PMD_MASK        (~(PMD_SIZE-1))
+
+/* PUD_SHIFT determines what a third-level page table entry can map */
+#define PUD_SHIFT       (PMD_SHIFT + PMD_INDEX_SIZE)
+#define PUD_SIZE        (1UL << PUD_SHIFT)
+#define PUD_MASK        (~(PUD_SIZE-1))
+
+/* PGDIR_SHIFT determines what a fourth-level page table entry can map */
+#define PGDIR_SHIFT     (PUD_SHIFT + PUD_INDEX_SIZE)
+#define PGDIR_SIZE      (1UL << PGDIR_SHIFT)
+#define PGDIR_MASK      (~(PGDIR_SIZE-1))
+
+/* PTE bits */
+#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
+#define _PAGE_F_GIX     _PAGE_GROUP_IX
+
+/* PTE flags to conserve for HPTE identification */
+#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | \
+                         _PAGE_SECONDARY | _PAGE_GROUP_IX)
+
+/* PAGE_MASK gives the right answer below, but only by accident */
+/* It should be preserving the high 48 bits and then specifically */
+/* preserving _PAGE_SECONDARY | _PAGE_GROUP_IX */
+#define _PAGE_CHG_MASK  (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY | \
+                         _PAGE_HPTEFLAGS)
+
+/* Bits to mask out from a PMD to get to the PTE page */
+#define PMD_MASKED_BITS         0
+/* Bits to mask out from a PUD to get to the PMD page */
+#define PUD_MASKED_BITS         0
+/* Bits to mask out from a PGD to get to the PUD page */
+#define PGD_MASKED_BITS         0
+
+/* shift to put page number into pte */
+#define PTE_RPN_SHIFT   (17)
+
+#define __real_pte(e,p)         ((real_pte_t)(e))
+#define __rpte_to_pte(r)        (r)
+#define __rpte_to_hidx(r,index) (pte_val((r)) >> 12)
+
+#define pte_iterate_hashed_subpages(rpte, psize, va, index, shift)       \
+        do {                                                             \
+                index = 0;                                               \
+                shift = mmu_psize_defs[psize].shift;                     \
+
+#define pte_iterate_hashed_end() } while(0)
+
+/*
+ * 4-level page tables related bits
+ */
+
+#define pgd_none(pgd)           (!pgd_val(pgd))
+#define pgd_bad(pgd)            (pgd_val(pgd) == 0)
+#define pgd_present(pgd)        (pgd_val(pgd) != 0)
+#define pgd_clear(pgdp)         (pgd_val(*(pgdp)) = 0)
+#define pgd_page(pgd)           (pgd_val(pgd) & ~PGD_MASKED_BITS)
+
+#define pud_offset(pgdp, addr)  \
+  (((pud_t *) pgd_page(*(pgdp))) + \
+    (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1)))
+
+#define pud_ERROR(e) \
+        printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pud_val(e))