[PATCH V2 11/11] powerpc/mm: Move hash specific pte bits to be top bits of RPN

[Aneesh Kumar K.V]

We don't support the full 57 bits of physical address and hence can overload
the top bits of RPN as hash specific pte bits.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/hash.h    | 18 ++++++------------
 arch/powerpc/include/asm/book3s/64/pgtable.h | 19 ++++++++++++++++---
 arch/powerpc/mm/hash_native_64.c             |  1 +
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index af3c88624d3a..33eb1a650317 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -6,20 +6,14 @@
  * Common bits between 4K and 64K pages in a linux-style PTE.
  * Additional bits may be defined in pgtable-hash64-*.h
  *
- * Note: We only support user read/write permissions. Supervisor always
- * have full read/write to pages above PAGE_OFFSET (pages below that
- * always use the user access permissions).
- *
- * We could create separate kernel read-only if we used the 3 PP bits
- * combinations that newer processors provide but we currently don't.
  */
-#define H_PAGE_BUSY		_RPAGE_SW1 /* software: PTE & hash are busy */
+#define H_PAGE_BUSY		_RPAGE_RPN45 /* software: PTE & hash are busy */
 #define H_PTE_NONE_MASK		_PAGE_HPTEFLAGS
-#define H_PAGE_F_GIX_SHIFT	57
-/* (7ul << 57) HPTE index within HPTEG */
-#define H_PAGE_F_GIX		(_RPAGE_RSV2 | _RPAGE_RSV3 | _RPAGE_RSV4)
-#define H_PAGE_F_SECOND		_RPAGE_RSV1	/* HPTE is in 2ndary HPTEG */
-#define H_PAGE_HASHPTE		_RPAGE_SW0	/* PTE has associated HPTE */
+#define H_PAGE_F_GIX_SHIFT	52
+/* (7ul << 53) HPTE index within HPTEG */
+#define H_PAGE_F_SECOND		_RPAGE_RPN44	/* HPTE is in 2ndary HPTEG */
+#define H_PAGE_F_GIX		(_RPAGE_RPN43 | _RPAGE_RPN42 | _RPAGE_RPN41)
+#define H_PAGE_HASHPTE		_RPAGE_RPN40	/* PTE has associated HPTE */
 /*
  * Max physical address bit we will use for now.
  *
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index eb82b60b5c89..3d104f8ad891 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -36,16 +36,29 @@
 #define _RPAGE_RSV2		0x0800000000000000UL
 #define _RPAGE_RSV3		0x0400000000000000UL
 #define _RPAGE_RSV4		0x0200000000000000UL
+
+#define _PAGE_PTE		0x4000000000000000UL	/* distinguishes PTEs from pointers */
+#define _PAGE_PRESENT		0x8000000000000000UL	/* pte contains a translation */
+
+/*
+ * Top and bottom bits of RPN which can be used by hash
+ * translation mode, because we expect them to be zero
+ * otherwise.
+ */
 #define _RPAGE_RPN0		0x01000
 #define _RPAGE_RPN1		0x02000
+#define _RPAGE_RPN45		0x0100000000000000UL
+#define _RPAGE_RPN44		0x0080000000000000UL
+#define _RPAGE_RPN43		0x0040000000000000UL
+#define _RPAGE_RPN42		0x0020000000000000UL
+#define _RPAGE_RPN41		0x0010000000000000UL
+#define _RPAGE_RPN40		0x0008000000000000UL
+
 /* Max physicall address bit as per radix table */
 #define _RPAGE_PA_MAX		57
 
 #define _PAGE_SOFT_DIRTY	_RPAGE_SW3 /* software: software dirty tracking */
 #define _PAGE_SPECIAL		_RPAGE_SW2 /* software: special page */
-
-#define _PAGE_PTE		0x4000000000000000UL	/* distinguishes PTEs from pointers */
-#define _PAGE_PRESENT		0x8000000000000000UL	/* pte contains a translation */
 /*
  * Drivers request for cache inhibited pte mapping using _PAGE_NO_CACHE
  * Instead of fixing all of them, add an alternate define which
diff --git a/arch/powerpc/mm/hash_native_64.c b/arch/powerpc/mm/hash_native_64.c
index cc332608e656..917a5a336441 100644
--- a/arch/powerpc/mm/hash_native_64.c
+++ b/arch/powerpc/mm/hash_native_64.c
@@ -246,6 +246,7 @@ static long native_hpte_insert(unsigned long hpte_group, unsigned long vpn,
 
 	__asm__ __volatile__ ("ptesync" : : : "memory");
 
+	BUILD_BUG_ON(H_PAGE_F_SECOND != (1ul  << (H_PAGE_F_GIX_SHIFT + 3)));
 	return i | (!!(vflags & HPTE_V_SECONDARY) << 3);
 }
 
-- 
2.7.4