User:Paolo Bonzini/Machine init sequence

Basic phases

• PHASE_NO_MACHINE:
  • Only backends can be created
  • No machines have compat props that affect the backends, so that's good
• machine-set command
• PHASE_MACHINE_CREATED:
  • Backends can be connected to on-board devices (how?)
  • Machine options include -smp, -boot, -m, -numa, -semihosting-config
• accel-set (can only be invoked again if it fails)
• PHASE_ACCEL_CREATED:
  • migration_object_init() can be called
  • plugins can be loaded
• finish-machine-init
• PHASE_MACHINE_INITIALIZED:
  • Devices can be created
  • The machine can be started ("cont") or incoming migration can proceed ("migrate_incoming")
  • x-exit-preconfig goes straight from PHASE_ACCEL_CREATED to PHASE_MACHINE_READY
• PHASE_MACHINE_READY
  • everything after qdev_machine_creation_done()

Missing: how to deal with machines starting in the paused state:

• to migrate them before they have been moved explicitly to PHASE_MACHINE_READY
• to allow various commands such as "info pci" without making them preconfig commands

Current machine init sequence

Up to CHECKPOINT_INIT

• Runstate is RUN_STATE_PRECONFIG or RUN_STATE_INMIGRATE
• Get machine_class
• Set machine compat props
• set_memory_options
• Options: -global
• replay_configure
• Options: -rtc
• Option: -pidfile
• qemu_init_main_loop
• Options: -sandbox, -name, -add-fd
• current_machine is created
• Options: -trace, -L
• Options: -smp
• Options: -mem-prealloc (requires current_machine->smp.cpus, but could look at -smp cpus directly)
• Options: -plugin (requires -smp)
• Handle default devices
  • Default device check (needs machine_class)
  • A bunch of checks for -daemonize
  • Add default devices to device_configs
• Create backends
  • Create displays
  • Create early objects
  • Options: -spice
  • Create chardevs
  • Create fsdevs
  • Create audiodevs
• Machine properties set
• Accelerators created and properties set
• migration_object_init
  • Wants current_machine->enforce_config_section, but that part can be done later though
• Initialize qtest server (QOMify)
• Parse bootorder and -machine kernel_filename/initrd_filename/kernel_cmdline
• cpu_timers_init() (can be done earlier)
• Create default network (move with other device_configs operations)
• net_init_clients
• Create late objects
• blk_mig_init, ram_mig_init, dirty_bitmap_mig_init (move to migration_object_init())
• Create monitors (why so late?)
• Create backends for -serial/-parallel/-debugcon
• get_default_vga_model, select_vgahw, select_watchdog

After CHECKPOINT_INIT

• qdev_machine_init()
  • Only creates /machine/peripheral and /machine/peripheral-anon
• Determine ram_size
• parse_numa_opts() -> set_numa_options()
• Preconfig monitor
  • set_numa_options (same as -numa but more powerful)

RUN_STATE_PRELAUNCH

• machine_run_board_init(current_machine)
  • On-board devices are created
  • Requires accelerator to be initialized
• Devices cannot be realized before this point (buses don't exist)
• Start VM
  • loadvm or incoming migration
  • Otherwise, vm_start()

First attempt at cleaned up sequence

Early option parsing

• Runstate is RUN_STATE_PRELAUNCH or RUN_STATE_INMIGRATE
• Desugaring: -mem-prealloc, -watchdog
• Options: -pidfile, -sandbox, -name, -add-fd, -trace, -L, -incoming defer
• replay_configure

Early initialization

• qemu_init_main_loop()
• cpu_timers_init()

Command-line processing part one

• Options: -global, -rtc
• Get machine_class
• Set machine compat props
• Handle default devices
  • Default device check (needs machine_class but not MS)
  • A bunch of checks for -daemonize
  • Add default devices to device_configs
• Create default network
• Create backends
  • Create displays
  • Create early objects
  • Options: -spice
  • Create chardevs
  • Create fsdevs
  • Create audiodevs
• Initialize qtest server

Machine creation

• set_memory_options
• current_machine is created
  • qdev_machine_init()
• Options: -smp
• Machine properties set
  • set current_migration->send_configuration as in migration_object_init

Accelerator creation

• Accelerators created and properties set
• Parse bootorder and -machine kernel_filename/initrd_filename/kernel_cmdline
• migration_object_init()
  • blk_mig_init, ram_mig_init, dirty_bitmap_mig_init

Late creation

• Options: -boot
• net_init_clients
• Create late objects
• Create monitors
• Create backends for -serial/-parallel/-debugcon
• get_default_vga_model, select_vgahw, select_watchdog
• Determine ram_size
  • parse_numa_opts() -> set_numa_options()

Leaving preconfig

• CHECKPOINT_INIT
• Options: -plugin (requires -smp, but must be before CPUs are created)
• machine_run_board_init(current_machine)
  • On-board devices are created
  • Requires accelerator to be initialized
• Devices cannot be realized before this point (buses don't exist)
• cont/migrate_incoming/loadvm complete initialization of the machine
  • everything starting with cpu_synchronize_all_post_init