整个simulate脚本就是在构建qemu仿真的参数

#!/usr/bin/env python3
#
# Copyright 2020, Data61, CSIRO (ABN 41 687 119 230)
#
# SPDX-License-Identifier: BSD-2-Clause
#

import subprocess #用于执行外部指令
import sys
import argparse
import time


def parse_args(): #使用parse_args函数解析命令行参数
    parser = argparse.ArgumentParser()
    parser.add_argument('-b', '--binary', dest="qemu_sim_binary", type=str,
                        help="QEMU binary", default="qemu-system-x86_64")
    parser.add_argument('-d', '--gdbserver', dest="qemu_gdbserver", action='store_true',
                        help="Tell QEMU to wait for gdb on port 1234")
    parser.add_argument('-M', '--machine', dest="qemu_sim_machine", type=str,
                        help="QEMU Machine", default="")
    parser.add_argument('-c', '--cpu', dest='qemu_sim_cpu', type=str,
                        help="QEMU CPU", default="Nehalem")
    parser.add_argument('-o', '--cpu-opt', dest='qemu_sim_cpu_opt', type=str,
                        help="QEMU CPU Options", default=",-vme,+pdpe1gb,-xsave,-xsaveopt,-xsavec,-fsgsbase,-invpcid,+syscall,+lm,enforce")
    parser.add_argument('-g', '--graphic', dest='qemu_sim_graphic_opt', type=str,
                        help="QEMU Graphic Options", default="-nographic")
    parser.add_argument('-s', '--serial', dest='qemu_sim_serial_opt', type=str,
                        help="QEMU Serial Options", default="-serial mon:stdio")
    parser.add_argument('-m', '--mem-size', dest='qemu_sim_mem_size', type=str,
                        help="QEMU Memory Size Option", default="512M")
    parser.add_argument('-a', '--args', dest='qemu_sim_args', type=str,
                        help="Arguments to pass onto QEMU", default="")
    parser.add_argument('-k', '--kernel', dest='qemu_sim_kernel_file', type=str,
                        help="Kernel file to pass onto QEMU", default="images/kernel-x86_64-pc99")
    parser.add_argument('-i', '--initrd', dest='qemu_sim_initrd_file', type=str,
                        help="Initrd file to pass onto QEMU", default="images/hello-world-image-x86_64-pc99")
    parser.add_argument("-n", '--dry-run', dest='dry_run', action='store_true',
                        help="Output command for QEMU (and GDB), but do not execute it")
    parser.add_argument('--extra-qemu-args', dest='qemu_sim_extra_args', type=str,
                        help="Additional arguments to pass onto QEMU", default="")
    parser.add_argument('--extra-cpu-opts', dest='qemu_sim_extra_cpu_opts', type=str,
                        help="Additional cpu options to append onto the existing CPU options",
                        default="")
    args = parser.parse_args()
    return args


def notice(message): #用输出带有程序名称前缀的log
    # Don't call this without initialising `progname`.
    assert(progname)
    sys.stderr.write("{}: {}".format(progname, message))
    sys.stderr.flush()


if __name__ == "__main__":
    args = parse_args()         #解析命令行参数并存储在args变量中
    progname = sys.argv[0]  #获取脚本自身的名称（progname）

    if args.qemu_sim_kernel_file == "": #根据参数选择使用哪个内核文件（默认为images/hello-world-image-x86_64-pc99）
        qemu_sim_images_entry = "-kernel " + args.qemu_sim_initrd_file
    else:
        qemu_sim_images_entry = "-kernel " + args.qemu_sim_kernel_file + " -initrd " + args.qemu_sim_initrd_file

    qemu_sim_cpu_entry = "" #构建CPU选项
    if args.qemu_sim_cpu != "":
        qemu_sim_cpu_entry = "-cpu " + args.qemu_sim_cpu + args.qemu_sim_cpu_opt + \
            ("," + args.qemu_sim_extra_cpu_opts if args.qemu_sim_extra_cpu_opts else "")

    qemu_sim_machine_entry = "" #构建QEMU机器选项
    if args.qemu_sim_machine:
        qemu_sim_machine_entry = "-machine " + args.qemu_sim_machine

    qemu_gdbserver_command = "" #如果选择启用GDB调试服务器，则添加相应的参数
    if args.qemu_gdbserver:
        qemu_gdbserver_command = "-s -S"

    qemu_sim_mem_size_entry = "-m size=" + args.qemu_sim_mem_size  #构建内存大小选项

    qemu_simulate_command_opts = [args.qemu_sim_binary, qemu_sim_machine_entry, qemu_sim_cpu_entry, args.qemu_sim_graphic_opt,
                                  args.qemu_sim_serial_opt, qemu_sim_mem_size_entry, args.qemu_sim_extra_args, qemu_sim_images_entry,
                                  qemu_gdbserver_command]  #构建额外的QEMU参数
    qemu_simulate_command = " ".join(qemu_simulate_command_opts) #构建完整的QEMU命令

    notice('QEMU command: ' + qemu_simulate_command) #输出构建的QEMU命令，如果选择了dry-run选项则仅输出不执行

    if args.dry_run:
        exit()

    if qemu_gdbserver_command != "": #如果启用了GDB调试服务器，则在端口1234上等待GDB连接
        notice('waiting for GDB on port 1234...')

    qemu_status = subprocess.call(qemu_simulate_command, shell=True) #运行QEMU虚拟机，并将返回状态存储在qemu_status中

    if qemu_status != 0: #如果QEMU启动失败，等待一段时间后尝试重置终端，以确保控制台的正确状态
        delay = 5  # in seconds
        # Force a newline onto the output stream.
        sys.stderr.write('\n')
        msg = "QEMU failed; resetting terminal in {d} seconds".format(d=delay) \
            + "--interrupt to abort\n"
        notice(msg)
    else:
        delay = 2  # in seconds #如果QEMU启动成功，也等待一段时间后重置终端

    time.sleep(delay)

    subprocess.call("tput reset", shell=True)

执行hello-world是RAM镜像文件中：

    parser.add_argument('-k', '--kernel', dest='qemu_sim_kernel_file', type=str,
                        help="Kernel file to pass onto QEMU", default="images/kernel-x86_64-pc99")
    parser.add_argument('-i', '--initrd', dest='qemu_sim_initrd_file', type=str,
                        help="Initrd file to pass onto QEMU", default="images/hello-world-image-x86_64-pc99")