notes/qemu_savevm_workflow at master · denis-plotnikov/notes · GitHub

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           migration_thread                       hmp_savevm
--> postcopy_start    --> migration_completion    --> qemu_savevm_state             qmp_xen_save_devices_state <-- (not interested)
       -->qemu_savevm_state_complete_precopy                                    qemu_save_device_state <--
                                               --> vmstate_save <--
                                                    --> vmstate_save_state:
                                                           save each field from a given VMStateDescription
                                                           to QEMUFile by calling field's put method
                                                        -->  field->info->put(f, addr, size):
								f: QEMUFile
								addr: offset from base address
								size: size of the field


WHERE savevm_state.handlers IS SET

instance_init
--> device_initfn
    --> device_set_realized
        --> vmstate_register_with_alias_id:
                insert a handler to savevm_state.handlers

VMStateDescription - a struct for storing device's state

VMStateDescription
	...
	VMStateField
            | ...
            | VMStateInfo
            |     | ...
            |     | VMStateInfo
            |     |    | name
            |     |    | (*get)
            |     |    | (*put)
            |     | ...
            | ...
	...