[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, 112 insertions, 35 deletions

diff --git a/include/asm-ppc64/page.h b/include/asm-ppc64/page.h
index d404431f0a9a..82ce187e5be8 100644
--- a/include/asm-ppc64/page.h
+++ b/include/asm-ppc64/page.h
@@ -13,32 +13,59 @@
 #include <linux/config.h>
 #include <asm/ppc_asm.h> /* for ASM_CONST */
 
-/* PAGE_SHIFT determines the page size */
-#define PAGE_SHIFT      12
-#define PAGE_SIZE       (ASM_CONST(1) << PAGE_SHIFT)
-#define PAGE_MASK       (~(PAGE_SIZE-1))
+/*
+ * We support either 4k or 64k software page size. When using 64k pages
+ * however, wether we are really supporting 64k pages in HW or not is
+ * irrelevant to those definitions. We always define HW_PAGE_SHIFT to 12
+ * as use of 64k pages remains a linux kernel specific, every notion of
+ * page number shared with the firmware, TCEs, iommu, etc... still assumes
+ * a page size of 4096.
+ */
+#ifdef CONFIG_PPC_64K_PAGES
+#define PAGE_SHIFT              16
+#else
+#define PAGE_SHIFT              12
+#endif
 
-#define SID_SHIFT       28
-#define SID_MASK        0xfffffffffUL
-#define ESID_MASK       0xfffffffff0000000UL
-#define GET_ESID(x)     (((x) >> SID_SHIFT) & SID_MASK)
+#define PAGE_SIZE               (ASM_CONST(1) << PAGE_SHIFT)
+#define PAGE_MASK               (~(PAGE_SIZE-1))
 
-#define HPAGE_SHIFT     24
-#define HPAGE_SIZE      ((1UL) << HPAGE_SHIFT)
-#define HPAGE_MASK      (~(HPAGE_SIZE - 1))
+/* HW_PAGE_SHIFT is always 4k pages */
+#define HW_PAGE_SHIFT           12
+#define HW_PAGE_SIZE            (ASM_CONST(1) << HW_PAGE_SHIFT)
+#define HW_PAGE_MASK            (~(HW_PAGE_SIZE-1))
 
-#ifdef CONFIG_HUGETLB_PAGE
+/* PAGE_FACTOR is the number of bits factor between PAGE_SHIFT and
+ * HW_PAGE_SHIFT, that is 4k pages
+ */
+#define PAGE_FACTOR             (PAGE_SHIFT - HW_PAGE_SHIFT)
+
+/* Segment size */
+#define SID_SHIFT               28
+#define SID_MASK                0xfffffffffUL
+#define ESID_MASK               0xfffffffff0000000UL
+#define GET_ESID(x)             (((x) >> SID_SHIFT) & SID_MASK)
 
+/* Large pages size */
+
+#ifndef __ASSEMBLY__
+extern unsigned int HPAGE_SHIFT;
+#define HPAGE_SIZE              ((1UL) << HPAGE_SHIFT)
+#define HPAGE_MASK              (~(HPAGE_SIZE - 1))
 #define HUGETLB_PAGE_ORDER      (HPAGE_SHIFT - PAGE_SHIFT)
+#endif /* __ASSEMBLY__ */
+
+#ifdef CONFIG_HUGETLB_PAGE
+
 
 #define HTLB_AREA_SHIFT         40
 #define HTLB_AREA_SIZE          (1UL << HTLB_AREA_SHIFT)
 #define GET_HTLB_AREA(x)        ((x) >> HTLB_AREA_SHIFT)
 
-#define LOW_ESID_MASK(addr, len)        (((1U << (GET_ESID(addr+len-1)+1)) \
-                                        - (1U << GET_ESID(addr))) & 0xffff)
-#define HTLB_AREA_MASK(addr, len)       (((1U << (GET_HTLB_AREA(addr+len-1)+1)) \
-                                        - (1U << GET_HTLB_AREA(addr))) & 0xffff)
+#define LOW_ESID_MASK(addr, len)    (((1U << (GET_ESID(addr+len-1)+1)) \
+                                      - (1U << GET_ESID(addr))) & 0xffff)
+#define HTLB_AREA_MASK(addr, len)   (((1U << (GET_HTLB_AREA(addr+len-1)+1)) \
+                                      - (1U << GET_HTLB_AREA(addr))) & 0xffff)
 
 #define ARCH_HAS_HUGEPAGE_ONLY_RANGE
 #define ARCH_HAS_PREPARE_HUGEPAGE_RANGE
@@ -114,7 +141,25 @@ static __inline__ void clear_page(void *addr)
         : "ctr", "memory");
 }
 
-extern void copy_page(void *to, void *from);
+extern void copy_4K_page(void *to, void *from);
+
+#ifdef CONFIG_PPC_64K_PAGES
+static inline void copy_page(void *to, void *from)
+{
+        unsigned int i;
+        for (i=0; i < (1 << (PAGE_SHIFT - 12)); i++) {
+                copy_4K_page(to, from);
+                to += 4096;
+                from += 4096;
+        }
+}
+#else /* CONFIG_PPC_64K_PAGES */
+static inline void copy_page(void *to, void *from)
+{
+        copy_4K_page(to, from);
+}
+#endif /* CONFIG_PPC_64K_PAGES */
+
 struct page;
 extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg);
 extern void copy_user_page(void *to, void *from, unsigned long vaddr, struct page *p);
@@ -124,43 +169,75 @@ extern void copy_user_page(void *to, void *from, unsigned long vaddr, struct pag
  * These are used to make use of C type-checking.  
  * Entries in the pte table are 64b, while entries in the pgd & pmd are 32b.
  */
-typedef struct { unsigned long pte; } pte_t;
-typedef struct { unsigned long pmd; } pmd_t;
-typedef struct { unsigned long pud; } pud_t;
-typedef struct { unsigned long pgd; } pgd_t;
-typedef struct { unsigned long pgprot; } pgprot_t;
 
+/* PTE level */
+typedef struct { unsigned long pte; } pte_t;
 #define pte_val(x)      ((x).pte)
-#define pmd_val(x)      ((x).pmd)
-#define pud_val(x)      ((x).pud)
-#define pgd_val(x)      ((x).pgd)
-#define pgprot_val(x)   ((x).pgprot)
-
 #define __pte(x)        ((pte_t) { (x) })
+
+/* 64k pages additionally define a bigger "real PTE" type that gathers
+ * the "second half" part of the PTE for pseudo 64k pages
+ */
+#ifdef CONFIG_PPC_64K_PAGES
+typedef struct { pte_t pte; unsigned long hidx; } real_pte_t;
+#else
+typedef struct { pte_t pte; } real_pte_t;
+#endif
+
+/* PMD level */
+typedef struct { unsigned long pmd; } pmd_t;
+#define pmd_val(x)      ((x).pmd)
 #define __pmd(x)        ((pmd_t) { (x) })
+
+/* PUD level exusts only on 4k pages */
+#ifndef CONFIG_PPC_64K_PAGES
+typedef struct { unsigned long pud; } pud_t;
+#define pud_val(x)      ((x).pud)
 #define __pud(x)        ((pud_t) { (x) })
+#endif
+
+/* PGD level */
+typedef struct { unsigned long pgd; } pgd_t;
+#define pgd_val(x)      ((x).pgd)
 #define __pgd(x)        ((pgd_t) { (x) })
+
+/* Page protection bits */
+typedef struct { unsigned long pgprot; } pgprot_t;
+#define pgprot_val(x)   ((x).pgprot)
 #define __pgprot(x)     ((pgprot_t) { (x) })
 
 #else
+
 /*
  * .. while these make it easier on the compiler
  */
-typedef unsigned long pte_t;
-typedef unsigned long pmd_t;
-typedef unsigned long pud_t;
-typedef unsigned long pgd_t;
-typedef unsigned long pgprot_t;
 
+typedef unsigned long pte_t;
 #define pte_val(x)      (x)
+#define __pte(x)        (x)
+
+#ifdef CONFIG_PPC_64K_PAGES
+typedef struct { pte_t pte; unsigned long hidx; } real_pte_t;
+#else
+typedef unsigned long real_pte_t;
+#endif
+
+
+typedef unsigned long pmd_t;
 #define pmd_val(x)      (x)
+#define __pmd(x)        (x)
+
+#ifndef CONFIG_PPC_64K_PAGES
+typedef unsigned long pud_t;
 #define pud_val(x)      (x)
+#define __pud(x)        (x)
+#endif
+
+typedef unsigned long pgd_t;
 #define pgd_val(x)      (x)
 #define pgprot_val(x)   (x)
 
-#define __pte(x)        (x)
-#define __pmd(x)        (x)
-#define __pud(x)        (x)
+typedef unsigned long pgprot_t;
 #define __pgd(x)        (x)
 #define __pgprot(x)     (x)