kvm: region_add and region_del is not called on updates

Attributes are not updated via region_add()/region_del(). Attribute changes
lead to a delete first, followed by a new add.

If this would ever not be the case, we would get an error when trying to
register the new slot.
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20171016144302.24284-6-david@redhat.com>
Tested-by: NJoe Clifford <joeclifford@gmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -721,8 +721,8 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
     ram = memory_region_get_ram_ptr(mr) + section->offset_within_region +
           (start_addr - section->offset_within_address_space);
 
-    mem = kvm_lookup_matching_slot(kml, start_addr, size);
     if (!add) {
+        mem = kvm_lookup_matching_slot(kml, start_addr, size);
         if (!mem) {
             return;
         }
@@ -741,12 +741,6 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
         return;
     }
 
-    if (mem) {
-        /* update the slot */
-        kvm_slot_update_flags(kml, mem, mr);
-        return;
-    }
-
     /* register the new slot */
     mem = kvm_alloc_slot(kml);
     mem->memory_size = size;