1 files changed, 51 insertions, 5 deletions
diff --git a/include/asm-ppc/mmu_context.h b/include/asm-ppc/mmu_context.h
index f4bd1e84f..89a649bb3 100644
--- a/include/asm-ppc/mmu_context.h
+++ b/include/asm-ppc/mmu_context.h
@@ -1,13 +1,59 @@
 #ifndef __PPC_MMU_CONTEXT_H
 #define __PPC_MMU_CONTEXT_H
 
+/* the way contexts are handled on the ppc they are vsid's and
+   don't need any special treatment right now.
+   perhaps I can defer flushing the tlb by keeping a list of
+   zombie vsid/context's and handling that through destroy_context
+   later -- Cort
+ */
+
+#define NO_CONTEXT	0
+#define LAST_CONTEXT	0xfffff
+
+extern int next_mmu_context;
+extern void mmu_context_overflow(void);
+extern void set_context(int context);
+
 /*
- * get a new mmu context.. PowerPC's don't know about contexts [yet]
+ * Allocating context numbers this way tends to spread out
+ * the entries in the hash table better than a simple linear
+ * allocation.
  */
-#define get_mmu_context(x) do { } while (0)
+#define MUNGE_CONTEXT(n)	(((n) * 897) & LAST_CONTEXT)
 
-#define init_new_context(mm)	do { } while(0)
-#define destroy_context(mm)	do { } while(0)
+/*
+ * Get a new mmu context for task tsk if necessary.
+ */
+#define get_mmu_context(tsk)					\
+do { 								\
+	struct mm_struct *mm = (tsk)->mm;			\
+	if (mm->context == NO_CONTEXT) {			\
+	        int i; \
+		if (next_mmu_context == LAST_CONTEXT)		\
+			mmu_context_overflow();			\
+		mm->context = MUNGE_CONTEXT(++next_mmu_context);\
+	 	if ( tsk == current )                           \
+			set_context(mm->context);               \
+	}							\
+} while (0)
 
-#endif
+/*
+ * Set up the context for a new address space.
+ */
+#define init_new_context(mm)	((mm)->context = NO_CONTEXT)
+
+/*
+ * We're finished using the context for an address space.
+ */
+#define destroy_context(mm)	do { } while (0)
 
+/*
+ * compute the vsid from the context and segment
+ * segments > 7 are kernel segments and their
+ * vsid is the segment -- Cort
+ */
+#define	VSID_FROM_CONTEXT(segment,context) \
+   ((segment < 8) ? ((segment) | (context)<<4) : (segment))
+
+#endif