PPC: Split context init/destroy functions

We need to reserve a context from KVM to make sure we have our own
segment space. While we did that split for Book3S_64 already, 32 bit
is still outstanding.

So let's split it now.

Signed-off-by: Alexander Graf <[e-mail]>
Acked-by: Benjamin Herrenschmidt <[e-mail]>
CC: Benjamin Herrenschmidt <[e-mail]>
Signed-off-by: Avi Kivity <[e-mail]>

arch/powerpc/include/asm/mmu_context.h

···
 extern void __destroy_context(int context_id);
 static inline void mmu_context_init(void) { }
 #else
+extern unsigned long __init_new_context(void);
+extern void __destroy_context(unsigned long context_id);
 extern void mmu_context_init(void);
 #endif
 

arch/powerpc/mm/mmu_context_hash32.c

···
 static unsigned long next_mmu_context;
 static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
 
-
-/*
- * Set up the context for a new address space.
- */
-int init_new_context(struct task_struct *t, struct mm_struct *mm)
+unsigned long __init_new_context(void)
 {
 	unsigned long ctx = next_mmu_context;
 
···
 			ctx = 0;
 	}
 	next_mmu_context = (ctx + 1) & LAST_CONTEXT;
-	mm->context.id = ctx;
+
+	return ctx;
+}
+EXPORT_SYMBOL_GPL(__init_new_context);
+
+/*
+ * Set up the context for a new address space.
+ */
+int init_new_context(struct task_struct *t, struct mm_struct *mm)
+{
+	mm->context.id = __init_new_context();
 
 	return 0;
 }
+
+/*
+ * Free a context ID. Make sure to call this with preempt disabled!
+ */
+void __destroy_context(unsigned long ctx)
+{
+	clear_bit(ctx, context_map);
+}
+EXPORT_SYMBOL_GPL(__destroy_context);
 
 /*
  * We're finished using the context for an address space.
···
 {
 	preempt_disable();
 	if (mm->context.id != NO_CONTEXT) {
-		clear_bit(mm->context.id, context_map);
+		__destroy_context(mm->context.id);
 		mm->context.id = NO_CONTEXT;
 	}
 	preempt_enable();