powerpc/mm/hash: Abstract context id allocation for KVM

KVM wants to be able to allocate an MMU context id, which it does
currently by calling __init_new_context().

We're about to rework that code, so provide a wrapper for KVM so it
can not worry about the details.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/mmu_context.h

@@ -51,7 +51,7 @@ static inline void switch_mmu_context(struct mm_struct *prev,
 	return switch_slb(tsk, next);
 }
 
-extern int __init_new_context(void);
+extern int hash__alloc_context_id(void);
 extern void __destroy_context(int context_id);
 static inline void mmu_context_init(void) { }
 #else

arch/powerpc/kvm/book3s_64_mmu_host.c

@@ -390,7 +390,7 @@ int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
 	struct kvmppc_vcpu_book3s *vcpu3s = to_book3s(vcpu);
 	int err;
 
-	err = __init_new_context();
+	err = hash__alloc_context_id();
 	if (err < 0)
 		return -1;
 	vcpu3s->context_id[0] = err;

arch/powerpc/mm/mmu_context_book3s64.c

@@ -30,7 +30,7 @@
 static DEFINE_SPINLOCK(mmu_context_lock);
 static DEFINE_IDA(mmu_context_ida);
 
-int __init_new_context(void)
+static int __init_new_context(void)
 {
 	int index;
 	int err;
@@ -57,7 +57,13 @@ again:
 
 	return index;
 }
-EXPORT_SYMBOL_GPL(__init_new_context);
+
+int hash__alloc_context_id(void)
+{
+	return __init_new_context();
+}
+EXPORT_SYMBOL_GPL(hash__alloc_context_id);
+
 static int radix__init_new_context(struct mm_struct *mm, int index)
 {
 	unsigned long rts_field;