[7/9] memory: convert memory_region_destroy to object_unparent

diff --git a/docs/memory.txt b/docs/memory.txt
index 5bdbdb3..b12f1f0 100644
--- a/docs/memory.txt
+++ b/docs/memory.txt
@@ -74,11 +74,15 @@  Region lifecycle
 ----------------
 
 A region is created by one of the constructor functions (memory_region_init*())
-and destroyed by the destructor (memory_region_destroy()).  In between,
-a region can be added to an address space by using memory_region_add_subregion()
-and removed using memory_region_del_subregion().  Region attributes may be
-changed at any point; they take effect once the region becomes exposed to the
-guest.
+and attached to an object.  It is then destroyed by object_unparent() or simply
+when the parent object dies.
+
+In between, a region can be added to an address space
+by using memory_region_add_subregion() and removed using
+memory_region_del_subregion().
+
+Region attributes may be changed at any point; they take effect once
+the region becomes exposed to the guest.
 
 Overlapping regions and priority
 --------------------------------
diff --git a/hw/display/vga.c b/hw/display/vga.c
index 68cfee2..65dab8d 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -176,7 +176,7 @@  static void vga_update_memory_access(VGACommonState *s)
 
     if (s->has_chain4_alias) {
         memory_region_del_subregion(s->legacy_address_space, &s->chain4_alias);
-        memory_region_destroy(&s->chain4_alias);
+        object_unparent(OBJECT(&s->chain4_alias));
         s->has_chain4_alias = false;
         s->plane_updated = 0xf;
     }
diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
index cb855c7..ee95963 100644
--- a/hw/i386/kvmvapic.c
+++ b/hw/i386/kvmvapic.c
@@ -584,7 +584,7 @@  static int vapic_map_rom_writable(VAPICROMState *s)
 
     if (s->rom_mapped_writable) {
         memory_region_del_subregion(as, &s->rom);
-        memory_region_destroy(&s->rom);
+        object_unparent(OBJECT(&s->rom));
     }
 
     /* grab RAM memory region (region @rom_paddr may still be pc.rom) */
diff --git a/hw/mips/gt64xxx_pci.c b/hw/mips/gt64xxx_pci.c
index 22f63ce..1f2fe5f 100644
--- a/hw/mips/gt64xxx_pci.c
+++ b/hw/mips/gt64xxx_pci.c
@@ -297,7 +297,7 @@  static void gt64120_pci_mapping(GT64120State *s)
       if (s->PCI0IO_length)
       {
           memory_region_del_subregion(get_system_memory(), &s->PCI0IO_mem);
-          memory_region_destroy(&s->PCI0IO_mem);
+          object_unparent(OBJECT(&s->PCI0IO_mem));
       }
       /* Map new IO address */
       s->PCI0IO_start = s->regs[GT_PCI0IOLD] << 21;
diff --git a/hw/misc/omap_gpmc.c b/hw/misc/omap_gpmc.c
index cddea24..fbbe2ff 100644
--- a/hw/misc/omap_gpmc.c
+++ b/hw/misc/omap_gpmc.c
@@ -436,7 +436,7 @@  static void omap_gpmc_cs_unmap(struct omap_gpmc_s *s, int cs)
     }
     memory_region_del_subregion(get_system_memory(), &f->container);
     memory_region_del_subregion(&f->container, omap_gpmc_cs_memregion(s, cs));
-    memory_region_destroy(&f->container);
+    object_unparent(OBJECT(&f->container));
 }
 
 void omap_gpmc_reset(struct omap_gpmc_s *s)
diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index 0b9eba0..af9ae1f 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -2266,7 +2266,7 @@  static void vfio_vga_quirk_teardown(VFIODevice *vdev)
         while (!QLIST_EMPTY(&vdev->vga.region[i].quirks)) {
             VFIOQuirk *quirk = QLIST_FIRST(&vdev->vga.region[i].quirks);
             memory_region_del_subregion(&vdev->vga.region[i].mem, &quirk->mem);
-            memory_region_destroy(&quirk->mem);
+            object_unparent(OBJECT(&quirk->mem));
             QLIST_REMOVE(quirk, next);
             g_free(quirk);
         }
@@ -2290,7 +2290,7 @@  static void vfio_bar_quirk_teardown(VFIODevice *vdev, int nr)
     while (!QLIST_EMPTY(&bar->quirks)) {
         VFIOQuirk *quirk = QLIST_FIRST(&bar->quirks);
         memory_region_del_subregion(&bar->mem, &quirk->mem);
-        memory_region_destroy(&quirk->mem);
+        object_unparent(OBJECT(&quirk->mem));
         QLIST_REMOVE(quirk, next);
         g_free(quirk);
     }
diff --git a/ioport.c b/ioport.c
index dce94a3..783a3ae 100644
--- a/ioport.c
+++ b/ioport.c
@@ -154,7 +154,7 @@  void portio_list_destroy(PortioList *piolist)
 
     for (i = 0; i < piolist->nr; ++i) {
         mrpio = container_of(piolist->regions[i], MemoryRegionPortioList, mr);
-        memory_region_destroy(&mrpio->mr);
+        object_unparent(OBJECT(&mrpio->mr));
         g_free(mrpio);
     }
     g_free(piolist->regions);
diff --git a/memory.c b/memory.c
index 64d7176..23c5269 100644
--- a/memory.c
+++ b/memory.c
@@ -1266,7 +1266,6 @@  static void memory_region_finalize(Object *obj)
 
 void memory_region_destroy(MemoryRegion *mr)
 {
-    object_unparent(OBJECT(mr));
 }