2 files changed, 15 insertions, 9 deletions

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 8f1d2fbec1d4..aee103b26d01 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -43,14 +43,6 @@
 #else /* ...!ASSEMBLY */
 
 #include <linux/stringify.h>
-#include <asm/sections.h>
-
-#define __addr_to_pcpu_ptr(addr)                                        \
-        (void *)((unsigned long)(addr) - (unsigned long)pcpu_base_addr  \
-                 + (unsigned long)__per_cpu_start)
-#define __pcpu_ptr_to_addr(ptr)                                         \
-        (void *)((unsigned long)(ptr) + (unsigned long)pcpu_base_addr   \
-                 - (unsigned long)__per_cpu_start)
 
 #ifdef CONFIG_SMP
 #define __percpu_arg(x)         "%%"__stringify(__percpu_seg)":%P" #x
diff --git a/mm/percpu.c b/mm/percpu.c
index bfe6a3afaf45..c6f38a2aface 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -46,7 +46,8 @@
  * - define CONFIG_HAVE_DYNAMIC_PER_CPU_AREA
  *
  * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
- *   regular address to percpu pointer and back
+ *   regular address to percpu pointer and back if they need to be
+ *   different from the default
  *
  * - use pcpu_setup_first_chunk() during percpu area initialization to
  *   setup the first chunk containing the kernel static percpu area
@@ -67,11 +68,24 @@
 #include <linux/workqueue.h>
 
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 #include <asm/tlbflush.h>
 
 #define PCPU_SLOT_BASE_SHIFT            5       /* 1-31 shares the same slot */
 #define PCPU_DFL_MAP_ALLOC              16      /* start a map with 16 ents */
 
+/* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
+#ifndef __addr_to_pcpu_ptr
+#define __addr_to_pcpu_ptr(addr)                                        \
+        (void *)((unsigned long)(addr) - (unsigned long)pcpu_base_addr  \
+                 + (unsigned long)__per_cpu_start)
+#endif
+#ifndef __pcpu_ptr_to_addr
+#define __pcpu_ptr_to_addr(ptr)                                         \
+        (void *)((unsigned long)(ptr) + (unsigned long)pcpu_base_addr   \
+                 - (unsigned long)__per_cpu_start)
+#endif
+
 struct pcpu_chunk {
         struct list_head        list;           /* linked to pcpu_slot lists */
         struct rb_node          rb_node;        /* key is chunk->vm->addr */