Features/3270

The 3270 is the classic 'green-screen' console (see the wikipedia article).

Code

• Initial posting: [1]
• Git: [2]

Implementation

The 3270 data stream is not implemented within QEMU; the code only implements tn3270 (a telnet extension; see RFCs 854 and 1576) and leaves the heavy lifting to an emulator (currently only tested with x3270).

Setup

This example setup is done with a Linux guest running in an s390x-ccw-virtio machine and the x3270 emulator running on a local Linux machine.

Prereqs

Guest

• Make sure that 3270 support is enabled in the kernel. You'll need CONFIG_TN3270 and at least one of CONFIG_TN3270_TTY (for additional ttys) or CONFIG_TN3270_CONSOLE (for a 3270 console).

Host

• You need to apply the patches or use the github branch (until the code has been integrated).

Other

• You need to have a copy of the x3270 emulator (should be packaged for most Linux distributions). Other 3270 emulators have not been tested.

Starting QEMU

• Add a tn3270 chardev to your QEMU command line (machine needs to be s390x-ccw-virtio). Example: -chardev socket,id=char_0,host=0.0.0.0,port=23,nowait,server,tn3270 -device x-terminal3270,chardev=char_0,devno=fe.0.000a,id=terminal_0
• Start QEMU. Your guest will be presented with a 3270 channel-attached device.

Guest Configuration

The guest will see the 3270 as a channel-attached device. With the example above, the device will show up as 0.0.000a.

Using 3270 as an additional tty

You can use the defined 3270 as an additional tty.

• Start the guest and log in via an alternative method (for example, via the sclp console).
• Enable the device. For the example above, use chccwdev -e 0.0.000a
• Find the respective device node, usually under /dev/3270/.
• Start a getty on that device node, for example via systemctl start serial-getty@3270-tty1.service
  • You may want to defer this step until after you connected via x3270, or you won't see the banner.