root@vagrant-ubuntu-trusty-64:~# cat centos7.json
{
  "builders":
  [
    {
      "type": "qemu",
      "iso_url": "http://centos.mirror.crcrepairs.com/7.0.1406/isos/x86_64/CentOS-7.0-1406-x86_64-NetInstall.iso",
      "iso_checksum": "96de4f38a2f07da51831153549c8bd0c",
      "iso_checksum_type": "md5",
      "output_directory": "output_centos_tdhtest",
      "ssh_wait_timeout": "30s",
      "shutdown_command": "shutdown -P now",
      "disk_size": 5000,
      "format": "qcow2",
      "headless": false,
      "accelerator": "kvm",
      "http_directory": "httpdir",
      "http_port_min": 10082,
      "http_port_max": 10089,
      "ssh_host_port_min": 2222,
      "ssh_host_port_max": 2229,
      "ssh_username": "centos",
      "ssh_password": "centos",
      "ssh_port": 22,
      "ssh_wait_timeout": "90m",
      "vm_name": "tdhtest",
      "net_device": "virtio-net",
      "disk_interface": "virtio",
      "boot_wait": "5s",
      "boot_command":
      [ " text ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos7-ks.cfg" ]

      "qemuargs": [
     [ "-m", "1024m" ],
    [ "--no-acpi", "" ],
    [
       "-netdev",
      "user,id=mynet0,",
      "hostfwd=hostip:hostport-guestip:guestport",
      ""
    ],
    [ "-device", "virtio-net,netdev=mynet0" ]
  ]

    }
  ]
}

root@vagrant-ubuntu-trusty-64:~# packer validate centos7.json
Failed to parse template: Error in line 32, char 6: invalid character '"' after object key:value pair
      "qemuargs": [