[PATCH v5 00/36] 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 v5 patch series of the v4 series located here:
https://lore.kernel.org/qemu-devel/cover.1738171076.git.maciej.szmigiero@oracle.com/

Changes from v3:
* Use "unsigned long" for VFIO bytes transferred counter to fixes
test issues on 32-bit platforms.

* Instead of adding BQL holding around qemu_loadvm_state_main() in
postcopy_ram_listen_thread() just add a TODO comment there.

* Drop patches for gracefully handling improperly terminated TLS session
and rely on recent Fabiano's changes to handle this case instead.

* Adapt how MULTIFD_FLAG_DEVICE_STATE value is defined for consistency with
neighboring flags.

* Return Error type and use migrate_set_error() to set it also for save
threads, much like it was previously done for load threads.

* Export SaveLiveCompletePrecopyThreadData and make save threads
take it directly instead of passing individual parameters stored there
to a thread entry point.

* Group all multifd device state save variables in
multifd_send_device_state variable allocated on demand instead of
using multifd-device-state.c globals.

* Export save threads abort flag via
multifd_device_state_save_thread_should_exit() getter function rather
than passing it directly.

* Separate VFIO multifd stuff into migration-multifd.{c,h} files.
Needed moving VFIO migration channel flags to vfio-common.h header file.

* Move x-migration-load-config-after-iter feature to a separate patch near
the end of the series.

* Move x-migration-max-queued-buffers feature to a yet another separate
patch near the end of the series.

* Introduce save/load common vfio_multifd_transfer_setup() and a getter
function for multifd transfer switch called vfio_multifd_transfer_enabled().

* Move introduction of VFIOMigration->multifd_transfer and
VFIODevice->migration_multifd_transfer into the very patch that introduces
the x-migration-multifd-transfer property.

* Introduce vfio_multifd_cleanup() for clearing migration->multifd.

* Split making x-migration-multifd-transfer mutable at runtime into
a separate patch.

* Rename vfio_switchover_start() to vfio_multifd_switchover_start() and
add a new vfio_switchover_start() in migration.c that calls that
vfio_multifd_switchover_start().

* Introduce VFIO_DEVICE_STATE_PACKET_VER_CURRENT.

* Don't print UINT32_MAX value in vfio_load_state_buffer().

* Introduce a new routine for parsing VFIO_MIG_FLAG_DEV_CONFIG_LOAD_READY.

* Add an Error parameter to vfio_save_complete_precopy_thread_config_state()
and propagate it from vfio_save_device_config_state() function that it calls.

* Update the VFIO developer doc in docs/devel/migration/vfio.rst.

* Add comments about how VFIO multifd threads are launched and from where
this happens. Also add comments how they are terminated.

* Other small changes, like renamed functions, added review tags, code
formatting, rebased on top of the latest QEMU git master, etc.

========================================================================

This patch set is targeting QEMU 10.0.

========================================================================

Maciej S. Szmigiero (35):
  migration: Clarify that {load,save}_cleanup handlers can run without
    setup
  thread-pool: Remove thread_pool_submit() function
  thread-pool: Rename AIO pool functions to *_aio() and data types to
    *Aio
  thread-pool: Implement generic (non-AIO) pool support
  migration: Add MIG_CMD_SWITCHOVER_START and its load handler
  migration: Add qemu_loadvm_load_state_buffer() and its handler
  migration: postcopy_ram_listen_thread() should take BQL for some calls
  error: define g_autoptr() cleanup function for the Error type
  migration: Add thread pool of optional load threads
  migration/multifd: Split packet into header and RAM data
  migration/multifd: Device state transfer support - receive side
  migration/multifd: Make multifd_send() thread safe
  migration/multifd: Add an explicit MultiFDSendData destructor
  migration/multifd: Device state transfer support - send side
  migration/multifd: Add multifd_device_state_supported()
  migration: Add save_live_complete_precopy_thread handler
  vfio/migration: Add load_device_config_state_start trace event
  vfio/migration: Convert bytes_transferred counter to atomic
  vfio/migration: Add vfio_add_bytes_transferred()
  vfio/migration: Move migration channel flags to vfio-common.h header
    file
  vfio/migration: Multifd device state transfer support - basic types
  vfio/migration: Multifd device state transfer support -
    VFIOStateBuffer(s)
  vfio/migration: Multifd device state transfer - add support checking
    function
  vfio/migration: Multifd device state transfer support - receive
    init/cleanup
  vfio/migration: Multifd device state transfer support - received
    buffers queuing
  vfio/migration: Multifd device state transfer support - load thread
  vfio/migration: Multifd device state transfer support - config loading
    support
  migration/qemu-file: Define g_autoptr() cleanup function for QEMUFile
  vfio/migration: Multifd device state transfer support - send side
  vfio/migration: Add x-migration-multifd-transfer VFIO property
  vfio/migration: Make x-migration-multifd-transfer VFIO property
    mutable
  hw/core/machine: Add compat for x-migration-multifd-transfer VFIO
    property
  vfio/migration: Max in-flight VFIO device state buffer count limit
  vfio/migration: Add x-migration-load-config-after-iter VFIO property
  vfio/migration: Update VFIO migration documentation

Peter Xu (1):
  migration/multifd: Make MultiFDSendData a struct

 docs/devel/migration/vfio.rst      |  80 ++-
 hw/core/machine.c                  |   2 +
 hw/vfio/meson.build                |   1 +
 hw/vfio/migration-multifd.c        | 757 +++++++++++++++++++++++++++++
 hw/vfio/migration-multifd.h        |  38 ++
 hw/vfio/migration.c                | 119 +++--
 hw/vfio/pci.c                      |  14 +
 hw/vfio/trace-events               |  11 +-
 include/block/aio.h                |   8 +-
 include/block/thread-pool.h        |  62 ++-
 include/hw/vfio/vfio-common.h      |  36 ++
 include/migration/client-options.h |   4 +
 include/migration/misc.h           |  25 +
 include/migration/register.h       |  52 +-
 include/qapi/error.h               |   2 +
 include/qemu/typedefs.h            |   5 +
 migration/colo.c                   |   3 +
 migration/meson.build              |   1 +
 migration/migration-hmp-cmds.c     |   2 +
 migration/migration.c              |   4 +-
 migration/migration.h              |   7 +
 migration/multifd-device-state.c   | 202 ++++++++
 migration/multifd-nocomp.c         |  30 +-
 migration/multifd.c                | 246 ++++++++--
 migration/multifd.h                |  74 ++-
 migration/options.c                |   9 +
 migration/qemu-file.h              |   2 +
 migration/savevm.c                 | 190 +++++++-
 migration/savevm.h                 |   6 +-
 migration/trace-events             |   1 +
 scripts/analyze-migration.py       |  11 +
 tests/unit/test-thread-pool.c      |   6 +-
 util/async.c                       |   6 +-
 util/thread-pool.c                 | 184 +++++--
 util/trace-events                  |   6 +-
 35 files changed, 2039 insertions(+), 167 deletions(-)
 create mode 100644 hw/vfio/migration-multifd.c
 create mode 100644 hw/vfio/migration-multifd.h
 create mode 100644 migration/multifd-device-state.c