pcie: remove mmconfig memory leak and wrap mmconfig update with transaction

This memory leak was introduced inadvertently by omitting object_unparent.
A better fix is to use the new memory_region_set_size instead of destroying
and recreating the MMIO region on the fly.

Also, ensure that unmapping and remapping the region is done atomically.
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/pci/pcie_host.c

@@ -88,6 +88,8 @@ static void pcie_host_init(Object *obj)
     PCIExpressHost *e = PCIE_HOST_BRIDGE(obj);
 
     e->base_addr = PCIE_BASE_ADDR_UNMAPPED;
+    memory_region_init_io(&e->mmio, OBJECT(e), &pcie_mmcfg_ops, e, "pcie-mmcfg-mmio",
+                          PCIE_MMCFG_SIZE_MAX);
 }
 
 void pcie_host_mmcfg_unmap(PCIExpressHost *e)
@@ -104,8 +106,7 @@ void pcie_host_mmcfg_init(PCIExpressHost *e, uint32_t size)
     assert(size >= PCIE_MMCFG_SIZE_MIN);
     assert(size <= PCIE_MMCFG_SIZE_MAX);
     e->size = size;
-    memory_region_init_io(&e->mmio, OBJECT(e), &pcie_mmcfg_ops, e,
-                          "pcie-mmcfg", e->size);
+    memory_region_set_size(&e->mmio, e->size);
 }
 
 void pcie_host_mmcfg_map(PCIExpressHost *e, hwaddr addr,
@@ -121,10 +122,12 @@ void pcie_host_mmcfg_update(PCIExpressHost *e,
                             hwaddr addr,
                             uint32_t size)
 {
+    memory_region_transaction_begin();
     pcie_host_mmcfg_unmap(e);
     if (enable) {
         pcie_host_mmcfg_map(e, addr, size);
     }
+    memory_region_transaction_commit();
 }
 
 static const TypeInfo pcie_host_type_info = {