powerpc/mm: Fix memory hotplug BUG() on radix

Memory hotplug is leading to hash page table calls, even on radix:

  arch_add_memory
    create_section_mapping
      htab_bolt_mapping
        BUG_ON(!ppc_md.hpte_insert);

To fix, refactor {create,remove}_section_mapping() into hash__ and
radix__ variants. Leave the radix versions stubbed for now.
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/hash.h

@@ -201,6 +201,10 @@ extern int __meminit hash__vmemmap_create_mapping(unsigned long start,
 					      unsigned long phys);
 extern void hash__vmemmap_remove_mapping(unsigned long start,
 				     unsigned long page_size);
+
+int hash__create_section_mapping(unsigned long start, unsigned long end);
+int hash__remove_section_mapping(unsigned long start, unsigned long end);
+
 #endif /* !__ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */

arch/powerpc/mm/hash_utils_64.c

@@ -747,7 +747,7 @@ static unsigned long __init htab_get_table_size(void)
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
-int create_section_mapping(unsigned long start, unsigned long end)
+int hash__create_section_mapping(unsigned long start, unsigned long end)
 {
 	int rc = htab_bolt_mapping(start, end, __pa(start),
 				   pgprot_val(PAGE_KERNEL), mmu_linear_psize,
@@ -761,7 +761,7 @@ int create_section_mapping(unsigned long start, unsigned long end)
 	return rc;
 }
 
-int remove_section_mapping(unsigned long start, unsigned long end)
+int hash__remove_section_mapping(unsigned long start, unsigned long end)
 {
 	int rc = htab_remove_mapping(start, end, mmu_linear_psize,
 				     mmu_kernel_ssize);

arch/powerpc/mm/pgtable-book3s64.c

@@ -126,3 +126,21 @@ void mmu_cleanup_all(void)
 	else if (mmu_hash_ops.hpte_clear_all)
 		mmu_hash_ops.hpte_clear_all();
 }
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+int create_section_mapping(unsigned long start, unsigned long end)
+{
+	if (radix_enabled())
+		return -ENODEV;
+
+	return hash__create_section_mapping(start, end);
+}
+
+int remove_section_mapping(unsigned long start, unsigned long end)
+{
+	if (radix_enabled())
+		return -ENODEV;
+
+	return hash__remove_section_mapping(start, end);
+}
+#endif /* CONFIG_MEMORY_HOTPLUG */