[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, 87 insertions, 0 deletions

diff --git a/include/asm-ppc64/pgtable-64k.h b/include/asm-ppc64/pgtable-64k.h
new file mode 100644
index 0000000000000..c5f437c86b3c7
--- /dev/null
+++ b/include/asm-ppc64/pgtable-64k.h
@@ -0,0 +1,87 @@
+#include <asm-generic/pgtable-nopud.h>
+
+
+#define PTE_INDEX_SIZE  12
+#define PMD_INDEX_SIZE  12
+#define PUD_INDEX_SIZE	0
+#define PGD_INDEX_SIZE  4
+
+#define PTE_TABLE_SIZE	(sizeof(real_pte_t) << PTE_INDEX_SIZE)
+#define PMD_TABLE_SIZE	(sizeof(pmd_t) << PMD_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_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))
+
+/* PGDIR_SHIFT determines what a third-level page table entry can map */
+#define PGDIR_SHIFT	(PMD_SHIFT + PMD_INDEX_SIZE)
+#define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
+#define PGDIR_MASK	(~(PGDIR_SIZE-1))
+
+/* Additional PTE bits (don't change without checking asm in hash_low.S) */
+#define _PAGE_HPTE_SUB	0x0ffff000 /* combo only: sub pages HPTE bits */
+#define _PAGE_HPTE_SUB0	0x08000000 /* combo only: first sub page */
+#define _PAGE_COMBO	0x10000000 /* this is a combo 4k page */
+#define _PAGE_F_SECOND  0x00008000 /* full page: hidx bits */
+#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)
+
+/* Shift to put page number into pte.
+ *
+ * That gives us a max RPN of 32 bits, which means a max of 48 bits
+ * of addressable physical space.
+ * We could get 3 more bits here by setting PTE_RPN_SHIFT to 29 but
+ * 32 makes PTEs more readable for debugging for now :)
+ */
+#define PTE_RPN_SHIFT	(32)
+#define PTE_RPN_MAX	(1UL << (64 - PTE_RPN_SHIFT))
+#define PTE_RPN_MASK	(~((1UL<<PTE_RPN_SHIFT)-1))
+
+/* _PAGE_CHG_MASK masks of bits that are to be preserved accross
+ * pgprot changes
+ */
+#define _PAGE_CHG_MASK	(PTE_RPN_MASK | _PAGE_HPTEFLAGS | _PAGE_DIRTY | \
+                         _PAGE_ACCESSED)
+
+/* Bits to mask out from a PMD to get to the PTE page */
+#define PMD_MASKED_BITS		0x1ff
+/* Bits to mask out from a PGD/PUD to get to the PMD page */
+#define PUD_MASKED_BITS		0x1ff
+
+#ifndef __ASSEMBLY__
+
+/* Manipulate "rpte" values */
+#define __real_pte(e,p) 	((real_pte_t) { \
+	(e), pte_val(*((p) + PTRS_PER_PTE)) })
+#define __rpte_to_hidx(r,index)	((pte_val((r).pte) & _PAGE_COMBO) ? \
+        (((r).hidx >> ((index)<<2)) & 0xf) : ((pte_val((r).pte) >> 12) & 0xf))
+#define __rpte_to_pte(r)	((r).pte)
+#define __rpte_sub_valid(rpte, index) \
+	(pte_val(rpte.pte) & (_PAGE_HPTE_SUB0 >> (index)))
+
+
+/* Trick: we set __end to va + 64k, which happens works for
+ * a 16M page as well as we want only one iteration
+ */
+#define pte_iterate_hashed_subpages(rpte, psize, va, index, shift)	    \
+        do {                                                                \
+                unsigned long __end = va + PAGE_SIZE;                       \
+                unsigned __split = (psize == MMU_PAGE_4K ||                 \
+				    psize == MMU_PAGE_64K_AP);              \
+                shift = mmu_psize_defs[psize].shift;                        \
+	        for (index = 0; va < __end; index++, va += (1 << shift)) {  \
+		        if (!__split || __rpte_sub_valid(rpte, index)) do { \
+
+#define pte_iterate_hashed_end() } while(0); } } while(0)
+
+
+#endif /*  __ASSEMBLY__ */