在JLI_Launch方法种就有jvm初始化

jboolean
LoadJavaVM(const char *jvmpath, InvocationFunctions *ifn)
{
    void *libjvm;

    JLI_TraceLauncher("JVM path is %s\n", jvmpath);

    libjvm = dlopen(jvmpath, RTLD_NOW + RTLD_GLOBAL);
    if (libjvm == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR1, __LINE__);
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    ifn->CreateJavaVM = (CreateJavaVM_t)
        dlsym(libjvm, "JNI_CreateJavaVM");
    if (ifn->CreateJavaVM == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    ifn->GetDefaultJavaVMInitArgs = (GetDefaultJavaVMInitArgs_t)
        dlsym(libjvm, "JNI_GetDefaultJavaVMInitArgs");
    if (ifn->GetDefaultJavaVMInitArgs == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    ifn->GetCreatedJavaVMs = (GetCreatedJavaVMs_t)
        dlsym(libjvm, "JNI_GetCreatedJavaVMs");
    if (ifn->GetCreatedJavaVMs == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    return JNI_TRUE;
}

ifn->CreateJavaVM 从jvm库文件获取对应的方法链接
在新线程执行方法JavaMain才会调用到库文件中的方法

if (!InitializeJVM(&vm, &env, &ifn)) {
    JLI_ReportErrorMessage(JVM_ERROR1);
    exit(1);
}

static jboolean
InitializeJVM(JavaVM **pvm, JNIEnv **penv, InvocationFunctions *ifn)
{
    JavaVMInitArgs args;
    jint r;

    memset(&args, 0, sizeof(args));
    args.version  = JNI_VERSION_1_2;
    args.nOptions = numOptions;
    args.options  = options;
    args.ignoreUnrecognized = JNI_FALSE;

    if (JLI_IsTraceLauncher()) {
        int i = 0;
        printf("JavaVM args:\n    ");
        printf("version 0x%08lx, ", (long)args.version);
        printf("ignoreUnrecognized is %s, ",
               args.ignoreUnrecognized ? "JNI_TRUE" : "JNI_FALSE");
        printf("nOptions is %ld\n", (long)args.nOptions);
        for (i = 0; i < numOptions; i++)
            printf("    option[%2d] = '%s'\n",
                   i, args.options[i].optionString);
    }

    r = ifn->CreateJavaVM(pvm, (void **)penv, &args);
    JLI_MemFree(options);
    return r == JNI_OK;
}

看一下具体调用
该方法可以找到CreateJavaVM_t实际连接的是JNI_CreateJavaVM
jni的部分可以在jni.cpp中查看到
JNI_IMPORT_OR_EXPORT jint JNICALL JNI_CreateJavaVM(JavaVM **vm, void **penv, void *args)
其调用的方法是
result = JNI_CreateJavaVM_inner(vm, penv, args);

static jint JNI_CreateJavaVM_inner(JavaVM **vm, void **penv, void *args) {
  HOTSPOT_JNI_CREATEJAVAVM_ENTRY((void **) vm, penv, args);

  jint result = JNI_ERR;
  DT_RETURN_MARK(CreateJavaVM, jint, (const jint&)result);

  if (Atomic::xchg(&vm_created, IN_PROGRESS) != NOT_CREATED) {
    return JNI_EEXIST;   // already created, or create attempt in progress
  }

  if (Atomic::xchg(&safe_to_recreate_vm, 0) == 0) {
    return JNI_ERR;
  }

  bool can_try_again = true;
  //在线程中创建jvm
  result = Threads::create_vm((JavaVMInitArgs*) args, &can_try_again);
  if (result == JNI_OK) {
    JavaThread *thread = JavaThread::current();
    assert(!thread->has_pending_exception(), "should have returned not OK");
    // thread is thread_in_vm here 
    //将引用赋值JavaVM，用于创建后其他线程调用
    *vm = (JavaVM *)(&main_vm);
    //暴露环境给外部使用
    *(JNIEnv**)penv = thread->jni_environment();
    // mark creation complete for other JNI ops
    Atomic::release_store(&vm_created, COMPLETE);
//jvmci及时编译器功能在jdk10以后出现的，在创建虚拟机后将编译器添加到一个线程上面
#if INCLUDE_JVMCI
    if (EnableJVMCI) {
      if (UseJVMCICompiler) {
        // JVMCI is initialized on a CompilerThread
        if (BootstrapJVMCI) {
          JavaThread* THREAD = thread; // For exception macros.
          JVMCICompiler* compiler = JVMCICompiler::instance(true, CATCH);
          compiler->bootstrap(THREAD);
          if (HAS_PENDING_EXCEPTION) {
            HandleMark hm(THREAD);
            vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
          }
        }
      }
    }
#endif

//jvmti作为事件监听器
    // Notify JVMTI
    if (JvmtiExport::should_post_thread_life()) {
       JvmtiExport::post_thread_start(thread);
    }

    JFR_ONLY(Jfr::on_thread_start(thread);)

    if (ReplayCompiles) ciReplay::replay(thread);

#ifdef ASSERT
    // Some platforms (like Win*) need a wrapper around these test
    // functions in order to properly handle error conditions.
    if (ErrorHandlerTest != 0) {
      VMError::controlled_crash(ErrorHandlerTest);
    }
#endif

    // Since this is not a JVM_ENTRY we have to set the thread state manually before leaving.
    ThreadStateTransition::transition_from_vm(thread, _thread_in_native);
    MACOS_AARCH64_ONLY(thread->enable_wx(WXExec));
  } else {
    // If create_vm exits because of a pending exception, exit with that
    // exception.  In the future when we figure out how to reclaim memory,
    // we may be able to exit with JNI_ERR and allow the calling application
    // to continue.
    if (Universe::is_fully_initialized()) {
      // otherwise no pending exception possible - VM will already have aborted
      Thread* current = Thread::current_or_null();
      if (current != nullptr) {
        JavaThread* THREAD = JavaThread::cast(current); // For exception macros.
        assert(HAS_PENDING_EXCEPTION, "must be - else no current thread exists");
        HandleMark hm(THREAD);
        vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
      }
    }

    if (can_try_again) {
      // reset safe_to_recreate_vm to 1 so that retrial would be possible
      safe_to_recreate_vm = 1;
    }

    // Creation failed. We must reset vm_created
    *vm = 0;
    *(JNIEnv**)penv = 0;
    // reset vm_created last to avoid race condition. Use OrderAccess to
    // control both compiler and architectural-based reordering.
    assert(vm_created == IN_PROGRESS, "must be");
    Atomic::release_store(&vm_created, NOT_CREATED);
  }

  // Flush stdout and stderr before exit.
  fflush(stdout);
  fflush(stderr);

  return result;

}

可以看出创建虚拟机没有新建线程，直接进行的初始化，继续看代码，
create_vm就是虚拟机创建的主方法，在方法里面进行了虚拟机参数的加载，系统的初始化比如动态链接库加载，gc参数加载等

jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
  extern void JDK_Version_init();

  // Preinitialize version info.
  VM_Version::early_initialize();

  // Check version
  if (!is_supported_jni_version(args->version)) return JNI_EVERSION;

  // Initialize library-based TLS
  //调用系统开辟当前线程的threadlocal的空间
  ThreadLocalStorage::init();

  // Initialize the output stream module
  //虚拟机系统输出初始化
  ostream_init();

  // Process java launcher properties.
  Arguments::process_sun_java_launcher_properties(args);

  // Initialize the os module
  //决定当前操作系统的API，获取操作系统分页大小设置到虚拟机，并且拿到时钟
  os::init();

  MACOS_AARCH64_ONLY(os::current_thread_enable_wx(WXWrite));

  // Record VM creation timing statistics
  TraceVmCreationTime create_vm_timer;
  create_vm_timer.start();

  // Initialize system properties.
  //初始化系统参数，比如路径set_boot_path将modules设置完成
  Arguments::init_system_properties();

  // So that JDK version can be used as a discriminator when parsing arguments
  JDK_Version_init();

  // Update/Initialize System properties after JDK version number is known
  Arguments::init_version_specific_system_properties();

  // Make sure to initialize log configuration *before* parsing arguments
  LogConfiguration::initialize(create_vm_timer.begin_time());

  // Parse arguments
  // Note: this internally calls os::init_container_support()
  jint parse_result = Arguments::parse(args);
  if (parse_result != JNI_OK) return parse_result;

  // Initialize NMT right after argument parsing to keep the pre-NMT-init window small.
  //内存追踪NMT，开启后jcmd可以获取内存分布情况
  MemTracker::initialize();

  //初始化处理器，内存大分页参数（最小的分页大小，提升性能用的），内存保护区域参数（内存用到这里很危险）
  os::init_before_ergo();

  //设置虚拟机的内存参数
  jint ergo_result = Arguments::apply_ergo();
  if (ergo_result != JNI_OK) return ergo_result;

  // Final check of all ranges after ergonomics which may change values.
  if (!JVMFlagLimit::check_all_ranges()) {
    return JNI_EINVAL;
  }

  // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
  bool constraint_result = JVMFlagLimit::check_all_constraints(JVMFlagConstraintPhase::AfterErgo);
  if (!constraint_result) {
    return JNI_EINVAL;
  }

  if (PauseAtStartup) {
    os::pause();
  }

  HOTSPOT_VM_INIT_BEGIN();

  // Timing (must come after argument parsing)
  TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));

  // Initialize the os module after parsing the args
  jint os_init_2_result = os::init_2();
  if (os_init_2_result != JNI_OK) return os_init_2_result;

#ifdef CAN_SHOW_REGISTERS_ON_ASSERT
  // Initialize assert poison page mechanism.
  if (ShowRegistersOnAssert) {
    initialize_assert_poison();
  }
#endif // CAN_SHOW_REGISTERS_ON_ASSERT
  //安全点pollingpage等参数设置
  SafepointMechanism::initialize();

  //如果是多cpu支持numa则设置并行的gc
  jint adjust_after_os_result = Arguments::adjust_after_os();
  if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;

  // Initialize output stream logging
  //ClassListWriter初始化，这个是APPCDS用于提升加载速度的
  ostream_init_log();

  // Launch -agentlib/-agentpath and converted -Xrun agents
  JvmtiAgentList::load_agents();

  // Initialize Threads state
  _number_of_threads = 0;
  _number_of_non_daemon_threads = 0;

  // Initialize global data structures and create system classes in heap
  //字面上在堆里初始化全局数据结构
  vm_init_globals();

#if INCLUDE_JVMCI
  if (JVMCICounterSize > 0) {
    JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtJVMCI);
    memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
  } else {
    JavaThread::_jvmci_old_thread_counters = nullptr;
  }
#endif // INCLUDE_JVMCI

  // Initialize OopStorage for threadObj
  JavaThread::_thread_oop_storage = OopStorageSet::create_strong("Thread OopStorage", mtThread);

  // Attach the main thread to this os thread
  JavaThread* main_thread = new JavaThread();
  main_thread->set_thread_state(_thread_in_vm);
  main_thread->initialize_thread_current();
  // must do this before set_active_handles
  main_thread->record_stack_base_and_size();
  main_thread->register_thread_stack_with_NMT();
  main_thread->set_active_handles(JNIHandleBlock::allocate_block());
  MACOS_AARCH64_ONLY(main_thread->init_wx());

  if (!main_thread->set_as_starting_thread()) {
    vm_shutdown_during_initialization(
                                      "Failed necessary internal allocation. Out of swap space");
    main_thread->smr_delete();
    *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
    return JNI_ENOMEM;
  }

  // Enable guard page *after* os::create_main_thread(), otherwise it would
  // crash Linux VM, see notes in os_linux.cpp.
  main_thread->stack_overflow_state()->create_stack_guard_pages();

  // Initialize Java-Level synchronization subsystem
  //c++中多线程相关初始化，synchronized关键字相关初始化，两个都跟java锁相关
  ObjectMonitor::Initialize();
  ObjectSynchronizer::initialize();

  // Initialize global modules
  //其中的classLoader_init1()加载了dll库，后面jni会用 universe_init()初始化了gc配置以及堆空间
  jint status = init_globals();
  if (status != JNI_OK) {
    main_thread->smr_delete();
    *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
    return status;
  }

  // Create WatcherThread as soon as we can since we need it in case
  // of hangs during error reporting.
  WatcherThread::start();

  // Add main_thread to threads list to finish barrier setup with
  // on_thread_attach.  Should be before starting to build Java objects in
  // init_globals2, which invokes barriers.
  {
    MutexLocker mu(Threads_lock);
    Threads::add(main_thread);
  }

  status = init_globals2();
  if (status != JNI_OK) {
    Threads::remove(main_thread, false);
    // It is possible that we managed to fully initialize Universe but have then
    // failed by throwing an exception. In that case our caller JNI_CreateJavaVM
    // will want to report it, so we can't delete the main thread.
    if (!main_thread->has_pending_exception()) {
      main_thread->smr_delete();
    }
    *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
    return status;
  }

  JFR_ONLY(Jfr::on_create_vm_1();)

  // Should be done after the heap is fully created
  main_thread->cache_global_variables();

  // Any JVMTI raw monitors entered in onload will transition into
  // real raw monitor. VM is setup enough here for raw monitor enter.
  JvmtiExport::transition_pending_onload_raw_monitors();

  // Create the VMThread
  { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));

    VMThread::create();
    VMThread* vmthread = VMThread::vm_thread();

    if (!os::create_thread(vmthread, os::vm_thread)) {
      vm_exit_during_initialization("Cannot create VM thread. "
                                    "Out of system resources.");
    }

    // Wait for the VM thread to become ready, and VMThread::run to initialize
    // Monitors can have spurious returns, must always check another state flag
    {
      MonitorLocker ml(Notify_lock);
      os::start_thread(vmthread);
      while (!vmthread->is_running()) {
        ml.wait();
      }
    }
  }

  assert(Universe::is_fully_initialized(), "not initialized");
  if (VerifyDuringStartup) {
    // Make sure we're starting with a clean slate.
    VM_Verify verify_op;
    VMThread::execute(&verify_op);
  }

  // We need this to update the java.vm.info property in case any flags used
  // to initially define it have been changed. This is needed for both CDS
  // since UseSharedSpaces may be changed after java.vm.info
  // is initially computed. See Abstract_VM_Version::vm_info_string().
  // This update must happen before we initialize the java classes, but
  // after any initialization logic that might modify the flags.
  Arguments::update_vm_info_property(VM_Version::vm_info_string());

  JavaThread* THREAD = JavaThread::current(); // For exception macros.
  HandleMark hm(THREAD);

  // Always call even when there are not JVMTI environments yet, since environments
  // may be attached late and JVMTI must track phases of VM execution
  JvmtiExport::enter_early_start_phase();

  // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
  JvmtiExport::post_early_vm_start();

  // Launch -Xrun agents early if EagerXrunInit is set
  if (EagerXrunInit) {
    JvmtiAgentList::load_xrun_agents();
  }
  //初始化java lang包的class
  initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);

  quicken_jni_functions();

  // No more stub generation allowed after that point.
  StubCodeDesc::freeze();

  // Set flag that basic initialization has completed. Used by exceptions and various
  // debug stuff, that does not work until all basic classes have been initialized.
  set_init_completed();

  LogConfiguration::post_initialize();
  Metaspace::post_initialize();
  MutexLocker::post_initialize();

  HOTSPOT_VM_INIT_END();

  // record VM initialization completion time
#if INCLUDE_MANAGEMENT
  Management::record_vm_init_completed();
#endif // INCLUDE_MANAGEMENT

  log_info(os)("Initialized VM with process ID %d", os::current_process_id());

  // Signal Dispatcher needs to be started before VMInit event is posted
  os::initialize_jdk_signal_support(CHECK_JNI_ERR);

  // Start Attach Listener if +StartAttachListener or it can't be started lazily
  if (!DisableAttachMechanism) {
    AttachListener::vm_start();
    if (StartAttachListener || AttachListener::init_at_startup()) {
      AttachListener::init();
    }
  }

  // Launch -Xrun agents if EagerXrunInit is not set.
  if (!EagerXrunInit) {
    JvmtiAgentList::load_xrun_agents();
  }

  Chunk::start_chunk_pool_cleaner_task();

  // Start the service thread
  // The service thread enqueues JVMTI deferred events and does various hashtable
  // and other cleanups.  Needs to start before the compilers start posting events.
  ServiceThread::initialize();

  // Start the monitor deflation thread:
  MonitorDeflationThread::initialize();

  // initialize compiler(s)
#if defined(COMPILER1) || COMPILER2_OR_JVMCI
#if INCLUDE_JVMCI
  bool force_JVMCI_intialization = false;
  if (EnableJVMCI) {
    // Initialize JVMCI eagerly when it is explicitly requested.
    // Or when JVMCILibDumpJNIConfig or JVMCIPrintProperties is enabled.
    force_JVMCI_intialization = EagerJVMCI || JVMCIPrintProperties || JVMCILibDumpJNIConfig;

    if (!force_JVMCI_intialization) {
      // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
      // compilations via JVMCI will not actually block until JVMCI is initialized.
      force_JVMCI_intialization = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
    }
  }
#endif
//初始化jit，方法中会判断系统是否启用，是才会启动新的线程
  CompileBroker::compilation_init_phase1(CHECK_JNI_ERR);
  // Postpone completion of compiler initialization to after JVMCI
  // is initialized to avoid timeouts of blocking compilations.
  if (JVMCI_ONLY(!force_JVMCI_intialization) NOT_JVMCI(true)) {
    CompileBroker::compilation_init_phase2();
  }
#endif

  // Start string deduplication thread if requested.
  if (StringDedup::is_enabled()) {
    StringDedup::start();
  }

  // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
  // It is done after compilers are initialized, because otherwise compilations of
  // signature polymorphic MH intrinsics can be missed
  // (see SystemDictionary::find_method_handle_intrinsic).
  initialize_jsr292_core_classes(CHECK_JNI_ERR);

  // This will initialize the module system.  Only java.base classes can be
  // loaded until phase 2 completes
  call_initPhase2(CHECK_JNI_ERR);

  JFR_ONLY(Jfr::on_create_vm_2();)

  // Always call even when there are not JVMTI environments yet, since environments
  // may be attached late and JVMTI must track phases of VM execution
  JvmtiExport::enter_start_phase();

  // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
  JvmtiExport::post_vm_start();

  // Final system initialization including security manager and system class loader
  call_initPhase3(CHECK_JNI_ERR);

  // cache the system and platform class loaders
  SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);

#if INCLUDE_CDS
  // capture the module path info from the ModuleEntryTable
  ClassLoader::initialize_module_path(THREAD);
  if (HAS_PENDING_EXCEPTION) {
    java_lang_Throwable::print(PENDING_EXCEPTION, tty);
    vm_exit_during_initialization("ClassLoader::initialize_module_path() failed unexpectedly");
  }
#endif

#if INCLUDE_JVMCI
  if (force_JVMCI_intialization) {
    JVMCI::initialize_compiler(CHECK_JNI_ERR);
    CompileBroker::compilation_init_phase2();
  }
#endif

  // Always call even when there are not JVMTI environments yet, since environments
  // may be attached late and JVMTI must track phases of VM execution
  JvmtiExport::enter_live_phase();

  // Make perfmemory accessible
  PerfMemory::set_accessible(true);

  // Notify JVMTI agents that VM initialization is complete - nop if no agents.
  JvmtiExport::post_vm_initialized();

  JFR_ONLY(Jfr::on_create_vm_3();)

#if INCLUDE_MANAGEMENT
  Management::initialize(THREAD);

  if (HAS_PENDING_EXCEPTION) {
    // management agent fails to start possibly due to
    // configuration problem and is responsible for printing
    // stack trace if appropriate. Simply exit VM.
    vm_exit(1);
  }
#endif // INCLUDE_MANAGEMENT

  StatSampler::engage();
  if (CheckJNICalls)                  JniPeriodicChecker::engage();

#if INCLUDE_RTM_OPT
  RTMLockingCounters::init();
#endif

  call_postVMInitHook(THREAD);
  // The Java side of PostVMInitHook.run must deal with all
  // exceptions and provide means of diagnosis.
  if (HAS_PENDING_EXCEPTION) {
    CLEAR_PENDING_EXCEPTION;
  }

  // Let WatcherThread run all registered periodic tasks now.
  // NOTE:  All PeriodicTasks should be registered by now. If they
  //   aren't, late joiners might appear to start slowly (we might
  //   take a while to process their first tick).
  WatcherThread::run_all_tasks();

  create_vm_timer.end();
#ifdef ASSERT
  _vm_complete = true;
#endif
  
  if (DumpSharedSpaces) {
    MetaspaceShared::preload_and_dump();
    ShouldNotReachHere();
  }

  return JNI_OK;
}