Hi all!

Here is a new migration parameter "local", which allows to
enable local migration of TAP virtio-net backend (and maybe other
devices and backends in future), including its properties and open
fds.

With this new option, management software doesn't need to initialize
new TAP and do a switch to it. Nothing should be done around
virtio-net in local migration: it just migrates and continues to use
same TAP device. So we avoid extra logic in management software, extra
allocations in kernel (for new TAP), and corresponding extra delay in
migration downtime.

v15:
03: add a-b by Peter
05: rebase on master, fix compat property to be part of 11.0

v15 pushed as branch up-tap-fd-migration-with-bk-opt
    at https://gitlab.com/vsementsov/qemu.git

Based-on: <20260318113144.15697-1-vsementsov@yandex-team.ru>
   "[PATCH v4 00/13] net: refactoring and fixes"

Vladimir Sementsov-Ogievskiy (8):
  net/tap: move vhost-net open() calls to tap_parse_vhost_fds()
  net/tap: move vhost initialization to tap_setup_vhost()
  qapi: add local migration parameter
  net: introduce vmstate_net_peer_backend
  virtio-net: support local migration of backend
  net/tap: support local migration with virtio-net
  tests/functional: add skipWithoutSudo() decorator
  tests/functional: add test_tap_migration

 hw/core/machine.c                             |   5 +
 hw/i386/pc_q35.c                              |   1 +
 hw/net/virtio-net.c                           | 137 +++++-
 include/hw/core/boards.h                      |   3 +
 include/hw/virtio/virtio-net.h                |   2 +
 include/migration/misc.h                      |   2 +
 include/net/net.h                             |   6 +
 migration/options.c                           |  18 +-
 net/net.c                                     |  47 ++
 net/tap.c                                     | 246 ++++++++--
 qapi/migration.json                           |  12 +-
 qapi/net.json                                 |  10 +-
 tests/functional/qemu_test/decorators.py      |  16 +
 tests/functional/x86_64/meson.build           |   1 +
 tests/functional/x86_64/test_tap_migration.py | 456 ++++++++++++++++++
 15 files changed, 911 insertions(+), 51 deletions(-)
 create mode 100755 tests/functional/x86_64/test_tap_migration.py

-- 
2.52.0