ARM64 disk images bigger than expected

Aarch64 images built by DIB are larger than expected (--image-size size -- image size in GB for the created image). For example, DIB outputs ~3.5 GB image when the desired image size is 3 GB.

An amphora image was created via Octavia's diskimage-crete.sh tool, a wrapper to DIB's disk-image-create tool:

  $ ./diskimage-create.sh -x -f -i centos-minimal -d 8 -a aarch64 -s 3

Full build log: https://cgoncalves.pt/trash/openstack/octavia/3d10a38e-c0f2-445e-a5d6-5be79c0521e8.txt

  $ qemu-img info amphora-x64-haproxy.qcow2
  image: amphora-x64-haproxy.qcow2
  file format: qcow2
  virtual size: 3.51 GiB (3771727872 bytes)
  disk size: 410 MiB
  cluster_size: 65536
  Format specific information:
      compat: 1.1
      compression type: zlib
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

Nova flavor set with 3GB disk:

[stack@ampere-hr350a-08 diskimage-create]$ openstack flavor create --id 9ad09cde-b703-43e0-988a-86585831f28b --disk 3 --vcpus 1 --ram 1024 --property "hw_rng:allowed='True'" m1.amphora
+----------------------------+--------------------------------------+
| Field | Value |
+----------------------------+--------------------------------------+
| OS-FLV-DISABLED:disabled | False |
| OS-FLV-EXT-DATA:ephemeral | 0 |
| disk | 3 |
| id | 9ad09cde-b703-43e0-988a-86585831f28b |
| name | m1.amphora |
| os-flavor-access:is_public | True |
| properties | hw_rng:allowed=''True'' |
| ram | 1024 |
| rxtx_factor | 1.0 |
| swap | |
| vcpus | 1 |
+----------------------------+--------------------------------------+

Nova fails to create the VMs:

nova.exception.FlavorDiskSmallerThanImage: Flavor's disk is too small for requested image. Flavor disk is 3221225472 bytes, image is 3771727872 bytes.

Mar 10 12:21:34 ampere-hr350a-08.khw4.lab.eng.bos.redhat.com octavia-worker[140215]: ERROR oslo_messaging.rpc.server [-] Exception during message handling: octavia.common.exceptions.ComputeBuildException: Failed to build compute instance due to: {'code': 500, 'created': '2021-03-10T17:21:29Z', 'message': "Build of instance 5b8c2928-aca0-40f6-89ba-a9812a218309 aborted: Flavor's disk is too small for requested image. Flavor disk is 3221225472 bytes, image is 3771727872 bytes.", 'details': 'Traceback (most recent call last):\n File "/opt/stack/nova/nova/compute/manager.py", line 2393, in _build_and_run_instance\n accel_info=accel_info)\n File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 3851, in spawn\n block_device_info=block_device_info)\n File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 4240, in _create_image\n injection_info, fallback_from_host)\n File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 4368, in _create_and_inject_local_root\n instance, size, fallback_from_host)\n File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 9968, in _try_fetch_image_cache\n trusted_certs=instance.trusted_certs)\n File "/opt/stack/nova/nova/virt/libvirt/imagebackend.py", line 275, in cache\n *args, **kwargs)\n File "/opt/stack/nova/nova/virt/libvirt/imagebackend.py", line 642, in create_image\n self.verify_base_size(base, size)\n File "/opt/stack/nova/nova/virt/libvirt/imagebackend.py", line 331, in verify_base_size\n flavor_size=size, image_size=base_size)\nnova.exception.FlavorDiskSmallerThanImage: Flavor\'s disk is too small for requested image. Flavor disk is 3221225472 bytes, image is 3771727872 bytes.\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n File "/opt/stack/nova/nova/compute/manager.py", line 2217, in _do_build_and_run_instance\n filter_properties, request_spec, accel_uuids)\n File "/opt/stack/nova/nova/compute/manager.py", line 2475, in _build_and_run_instance\n reason=e.format_message())\nnova.exception.BuildAbortException: Build of instance 5b8c2928-aca0-40f6-89ba-a9812a218309 aborted: Flavor\'s disk is too small for requested image. Flavor disk is 3221225472 bytes, image is 3771727872 bytes.\n'}