[PATCH v2 00/17] Multifd 🔀 device state transfer support with VFIO consumer

["Maciej S. Szmigiero" <mail@maciej.szmigiero.name>]

From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

This is an updated v2 patch series of the v1 series located here:
https://lore.kernel.org/qemu-devel/cover.1718717584.git.maciej.szmigiero@oracle.com/

Changes from v1:
* Extended the QEMU thread-pool with non-AIO (generic) pool support,
implemented automatic memory management support for its work element
function argument.

* Introduced a multifd device state save thread pool, ported the VFIO
multifd device state save implementation to use this thread pool instead
of VFIO internally managed individual threads.

* Re-implemented on top of Fabiano's v4 multifd sender refactor patch set from
https://lore.kernel.org/qemu-devel/20240823173911.6712-1-farosas@suse.de/

* Moved device state related multifd code to new multifd-device-state.c
file where it made sense.

* Implemented a max in-flight VFIO device state buffer count limit to
allow capping the maximum recipient memory usage.

* Removed unnecessary explicit memory barriers from multifd_send().

* A few small changes like updated comments, code formatting,
fixed zero-copy RAM multifd bytes transferred counter under-counting, etc.


For convenience, this patch set is also available as a git tree:
https://github.com/maciejsszmigiero/qemu/tree/multifd-device-state-transfer-vfio

Based-on: <20240823173911.6712-1-farosas@suse.de>


Maciej S. Szmigiero (17):
  vfio/migration: Add save_{iterate,complete_precopy}_started trace
    events
  migration/ram: Add load start trace event
  migration/multifd: Zero p->flags before starting filling a packet
  thread-pool: Add a DestroyNotify parameter to
    thread_pool_submit{,_aio)()
  thread-pool: Implement non-AIO (generic) pool support
  migration: Add save_live_complete_precopy_{begin,end} handlers
  migration: Add qemu_loadvm_load_state_buffer() and its handler
  migration: Add load_finish handler and associated functions
  migration/multifd: Device state transfer support - receive side
  migration/multifd: Convert multifd_send()::next_channel to atomic
  migration/multifd: Add an explicit MultiFDSendData destructor
  migration/multifd: Device state transfer support - send side
  migration/multifd: Add migration_has_device_state_support()
  migration: Add save_live_complete_precopy_thread handler
  vfio/migration: Multifd device state transfer support - receive side
  vfio/migration: Add x-migration-multifd-transfer VFIO property
  vfio/migration: Multifd device state transfer support - send side

 backends/tpm/tpm_backend.c       |   2 +-
 block/file-win32.c               |   2 +-
 hw/9pfs/coth.c                   |   3 +-
 hw/ppc/spapr_nvdimm.c            |   4 +-
 hw/vfio/migration.c              | 520 ++++++++++++++++++++++++++++++-
 hw/vfio/pci.c                    |   9 +
 hw/vfio/trace-events             |  14 +-
 hw/virtio/virtio-pmem.c          |   2 +-
 include/block/thread-pool.h      |  12 +-
 include/hw/vfio/vfio-common.h    |  22 ++
 include/migration/misc.h         |  15 +
 include/migration/register.h     |  97 ++++++
 include/qemu/typedefs.h          |   4 +
 migration/meson.build            |   1 +
 migration/migration.c            |   6 +
 migration/migration.h            |   3 +
 migration/multifd-device-state.c | 193 ++++++++++++
 migration/multifd-nocomp.c       |   9 +-
 migration/multifd-qpl.c          |   2 +-
 migration/multifd-uadk.c         |   2 +-
 migration/multifd-zlib.c         |   2 +-
 migration/multifd-zstd.c         |   2 +-
 migration/multifd.c              | 249 ++++++++++++---
 migration/multifd.h              |  65 +++-
 migration/ram.c                  |   1 +
 migration/savevm.c               | 152 ++++++++-
 migration/savevm.h               |   7 +
 migration/trace-events           |   1 +
 tests/unit/test-thread-pool.c    |   8 +-
 util/thread-pool.c               |  83 ++++-
 30 files changed, 1406 insertions(+), 86 deletions(-)
 create mode 100644 migration/multifd-device-state.c