diff --git a/docs/system/s390x/3270.rst b/docs/system/s390x/3270.rst index 1774cdcadf..0554a70a9f 100644 --- a/docs/system/s390x/3270.rst +++ b/docs/system/s390x/3270.rst @@ -1,9 +1,15 @@ 3270 devices ============ -QEMU supports connecting an external 3270 terminal emulator (such as -``x3270``) to make a single 3270 device available to a guest. Note that this -supports basic features only. +The 3270 is the classic 'green-screen' console of the mainframes (see the +`IBM 3270 Wikipedia article `__). + +The 3270 data stream is not implemented within QEMU; the device only provides +TN3270 (a telnet extension; see `RFC 854 `__ +and `RFC 1576 `__) and leaves the heavy +lifting to an external 3270 terminal emulator (such as ``x3270``) to make a +single 3270 device available to a guest. Note that this supports basic +features only. To provide a 3270 device to a guest, create a ``x-terminal3270`` linked to a ``tn3270`` chardev. The guest will see a 3270 channel device. In order @@ -12,10 +18,14 @@ to actually be able to use it, attach the ``x3270`` emulator to the chardev. Example configuration --------------------- +* Make sure that 3270 support is enabled in the guest's Linux kernel. You need + ``CONFIG_TN3270`` and at least one of ``CONFIG_TN3270_TTY`` (for additional + ttys) or ``CONFIG_TN3270_CONSOLE`` (for a 3270 console). + * Add a ``tn3270`` chardev and a ``x-terminal3270`` to the QEMU command line:: - -chardev socket,id=char_0,host=0.0.0.0,port=2300,nowait,server,tn3270 - -device x-terminal3270,chardev=char_0,devno=fe.0.000a,id=terminal_0 + -chardev socket,id=ch0,host=0.0.0.0,port=2300,nowait,server,tn3270 + -device x-terminal3270,chardev=ch0,devno=fe.0.000a,id=terminal0 * Start the guest. In the guest, use ``chccwdev -e 0.0.000a`` to enable the device. @@ -29,4 +39,25 @@ Example configuration systemctl start serial-getty@3270-tty1.service -This should get you an addtional tty for logging into the guest. + This should get you an additional tty for logging into the guest. + +* If you want to use the 3270 device as the Linux kernel console instead of + an additional tty, you can also append ``conmode=3270 condev=000a`` to + the guest's kernel command line. The kernel then should use the 3270 as + console after the next boot. + +Restrictions +------------ + +3270 support is very basic. In particular: + +* Only one 3270 device is supported. + +* It has only been tested with Linux guests and the x3270 emulator. + +* TLS/SSL is not supported. + +* Resizing on reattach is not supported. + +* Multiple commands in one inbound buffer (for example, when the reset key + is pressed while the network is slow) are not supported.