[PATCH] powerpc/mm: fix memory hotplug BUG() on radix

[PATCH] powerpc/mm: fix memory hotplug BUG() on radix

[Reza Arbab]

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>
---
It was suggested that this fix be separated from the rest of the
set which implements the radix page mapping/unmapping.

 arch/powerpc/include/asm/book3s/64/hash.h |  5 +++++
 arch/powerpc/mm/hash_utils_64.c           |  4 ++--
 arch/powerpc/mm/pgtable-book3s64.c        | 18 ++++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index f61cad3..dd90574 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -201,6 +201,11 @@ 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);
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+int hash__create_section_mapping(unsigned long start, unsigned long end);
+int hash__remove_section_mapping(unsigned long start, unsigned long end);
+#endif /* CONFIG_MEMORY_HOTPLUG */
 #endif /* !__ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index b9a062f..96a4fb7 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -743,7 +743,7 @@ 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,
@@ -757,7 +757,7 @@ 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);
diff --git a/arch/powerpc/mm/pgtable-book3s64.c b/arch/powerpc/mm/pgtable-book3s64.c
index ebf9782..653ff6c 100644
--- a/arch/powerpc/mm/pgtable-book3s64.c
+++ b/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 */
-- 
1.8.3.1

Re: powerpc/mm: fix memory hotplug BUG() on radix

[Michael Ellerman]

On Tue, 2017-01-03 at 20:39:51 UTC, Reza Arbab wrote:
> 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>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/32b53c012e0bfe20b2745962a89db0

cheers