powerpc/mm: Implement _PAGE_SPECIAL & pte_special() for 64-bit

Implement _PAGE_SPECIAL and pte_special() for 64-bit powerpc. This bit will
be used by the fast get_user_pages() to differenciate PTEs that correspond
to a valid struct page from special mappings that don't such as IO mappings
obtained via io_remap_pfn_ranges().

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 6 insertions, 2 deletions

diff --git a/include/asm-powerpc/pgtable-4k.h b/include/asm-powerpc/pgtable-4k.h
index c9601dfb4a1e..6b18ba9d2d85 100644
--- a/include/asm-powerpc/pgtable-4k.h
+++ b/include/asm-powerpc/pgtable-4k.h
@@ -46,6 +46,8 @@
 #define _PAGE_GROUP_IX  0x7000 /* software: HPTE index within group */
 #define _PAGE_F_SECOND  _PAGE_SECONDARY
 #define _PAGE_F_GIX     _PAGE_GROUP_IX
+#define _PAGE_SPECIAL   0x10000 /* software: special page */
+#define __HAVE_ARCH_PTE_SPECIAL
 
 /* PTE flags to conserve for HPTE identification */
 #define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | \
diff --git a/include/asm-powerpc/pgtable-64k.h b/include/asm-powerpc/pgtable-64k.h
index 7e54adb35596..07b0d8f09cb6 100644
--- a/include/asm-powerpc/pgtable-64k.h
+++ b/include/asm-powerpc/pgtable-64k.h
@@ -70,6 +70,8 @@ static inline struct subpage_prot_table *pgd_subpage_prot(pgd_t *pgd)
 #define PGDIR_MASK      (~(PGDIR_SIZE-1))
 
 /* Additional PTE bits (don't change without checking asm in hash_low.S) */
+#define __HAVE_ARCH_PTE_SPECIAL
+#define _PAGE_SPECIAL   0x00000400 /* software: special page */
 #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 */
diff --git a/include/asm-powerpc/pgtable-ppc64.h b/include/asm-powerpc/pgtable-ppc64.h
index ba8000352b9a..5fc78c0be302 100644
--- a/include/asm-powerpc/pgtable-ppc64.h
+++ b/include/asm-powerpc/pgtable-ppc64.h
@@ -245,7 +245,7 @@ static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_RW;}
 static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY;}
 static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED;}
 static inline int pte_file(pte_t pte) { return pte_val(pte) & _PAGE_FILE;}
-static inline int pte_special(pte_t pte) { return 0; }
+static inline int pte_special(pte_t pte) { return pte_val(pte) & _PAGE_SPECIAL; }
 
 static inline void pte_uncache(pte_t pte) { pte_val(pte) |= _PAGE_NO_CACHE; }
 static inline void pte_cache(pte_t pte)   { pte_val(pte) &= ~_PAGE_NO_CACHE; }
@@ -265,7 +265,7 @@ static inline pte_t pte_mkyoung(pte_t pte) {
 static inline pte_t pte_mkhuge(pte_t pte) {
         return pte; }
 static inline pte_t pte_mkspecial(pte_t pte) {
-        return pte; }
+        pte_val(pte) |= _PAGE_SPECIAL; return pte; }
 static inline unsigned long pte_pgprot(pte_t pte)
 {
         return __pgprot(pte_val(pte)) & PAGE_PROT_BITS;