diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
index 5f8c2bd..839efae 100644
--- a/arch/powerpc/include/asm/mmu-hash64.h
+++ b/arch/powerpc/include/asm/mmu-hash64.h
@@ -381,7 +381,27 @@ extern void slb_set_size(u16 size);
  * hash collisions.
  */
 
-#define CONTEXT_BITS		19
+/*
+ * Be careful with this value. This determines the VSID_MODULUS_*  and that
+ * need to be co-prime with VSID_MULTIPLIER*
+ */
+#if defined(CONFIG_POWER6_CPU) || defined(CONFIG_POWER7_CPU)
+/*
+ * Even if cpu support 68 bits, we limit this to 66 because
+ * we support only 2^19 context.
+ */
+#define MAX_VIRTUAL_ADDR_BITS 66
+#else
+/* power4,power 5 and cell is 65 */
+#define MAX_VIRTUAL_ADDR_BITS 65
+#endif
+
+/*
+ * One bit is taken by the kernel, only the rest of space is available for the
+ * user space.
+ */
+#define CONTEXT_BITS		(MAX_VIRTUAL_ADDR_BITS - \
+				 (USER_ESID_BITS + SID_SHIFT + 1))
 #define USER_ESID_BITS		18
 #define USER_ESID_BITS_1T	6