diff --git a/exec.c b/exec.c
index ff3cb3e25b8264d8934ac0661d28b06b13ccbbb6..d9827ef840aae6b8e5f5d83bc24f69ffdf08d24e 100644
--- a/exec.c
+++ b/exec.c
@@ -1491,8 +1491,8 @@ hwaddr memory_region_section_get_iotlb(CPUState *cpu,
 
 #if !defined(CONFIG_USER_ONLY)
 
-static int subpage_register (subpage_t *mmio, uint32_t start, uint32_t end,
-                             uint16_t section);
+static int subpage_register(subpage_t *mmio, uint32_t start, uint32_t end,
+                            uint16_t section);
 static subpage_t *subpage_init(FlatView *fv, hwaddr base);
 
 static void *(*phys_mem_alloc)(size_t size, uint64_t *align, bool shared) =
@@ -2913,8 +2913,8 @@ static const MemoryRegionOps subpage_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
-static int subpage_register (subpage_t *mmio, uint32_t start, uint32_t end,
-                             uint16_t section)
+static int subpage_register(subpage_t *mmio, uint32_t start, uint32_t end,
+                            uint16_t section)
 {
     int idx, eidx;
 
@@ -2937,6 +2937,7 @@ static subpage_t *subpage_init(FlatView *fv, hwaddr base)
 {
     subpage_t *mmio;
 
+    /* mmio->sub_section is set to PHYS_SECTION_UNASSIGNED with g_malloc0 */
     mmio = g_malloc0(sizeof(subpage_t) + TARGET_PAGE_SIZE * sizeof(uint16_t));
     mmio->fv = fv;
     mmio->base = base;
@@ -2947,7 +2948,6 @@ static subpage_t *subpage_init(FlatView *fv, hwaddr base)
     printf("%s: %p base " TARGET_FMT_plx " len %08x\n", __func__,
            mmio, base, TARGET_PAGE_SIZE);
 #endif
-    subpage_register(mmio, 0, TARGET_PAGE_SIZE-1, PHYS_SECTION_UNASSIGNED);
 
     return mmio;
 }