[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, 11 insertions, 7 deletions

diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index b0fc822ec29f..dfe7fa37b41a 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -188,12 +188,21 @@ static void zero_ctor(void *addr, kmem_cache_t *cache, unsigned long flags)
         memset(addr, 0, kmem_cache_size(cache));
 }
 
+#ifdef CONFIG_PPC_64K_PAGES
+static const int pgtable_cache_size[2] = {
+        PTE_TABLE_SIZE, PGD_TABLE_SIZE
+};
+static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
+        "pte_pmd_cache", "pgd_cache",
+};
+#else
 static const int pgtable_cache_size[2] = {
         PTE_TABLE_SIZE, PMD_TABLE_SIZE
 };
 static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
         "pgd_pte_cache", "pud_pmd_cache",
 };
+#endif /* CONFIG_PPC_64K_PAGES */
 
 kmem_cache_t *pgtable_cache[ARRAY_SIZE(pgtable_cache_size)];
 
@@ -201,19 +210,14 @@ void pgtable_cache_init(void)
 {
         int i;
 
-        BUILD_BUG_ON(PTE_TABLE_SIZE != pgtable_cache_size[PTE_CACHE_NUM]);
-        BUILD_BUG_ON(PMD_TABLE_SIZE != pgtable_cache_size[PMD_CACHE_NUM]);
-        BUILD_BUG_ON(PUD_TABLE_SIZE != pgtable_cache_size[PUD_CACHE_NUM]);
-        BUILD_BUG_ON(PGD_TABLE_SIZE != pgtable_cache_size[PGD_CACHE_NUM]);
-
         for (i = 0; i < ARRAY_SIZE(pgtable_cache_size); i++) {
                 int size = pgtable_cache_size[i];
                 const char *name = pgtable_cache_name[i];
 
                 pgtable_cache[i] = kmem_cache_create(name,
                                                      size, size,
-                                                     SLAB_HWCACHE_ALIGN
-                                                     | SLAB_MUST_HWCACHE_ALIGN,
+                                                     SLAB_HWCACHE_ALIGN |
+                                                     SLAB_MUST_HWCACHE_ALIGN,
                                                      zero_ctor,
                                                      NULL);
                 if (! pgtable_cache[i])