IVSHMEM 기반 IPM

.. zephyr:code-sample:: ipm-ivshmem
   :name: IPM over IVSHMEM
   :relevant-api: ipm_interface

   Implement inter-processor mailbox (IPM) over IVSHMEM (Inter-VM shared memory)

Prerequisites
*************

* QEMU needs to available.

ivshmem-server needs to be available and running. The server is available in
Zephyr SDK or pre-built in some distributions. Otherwise, it is available in
QEMU source tree.

ivshmem-client needs to be available as it is employed in this sample as an
external application. The same conditions of ivshmem-server apply to the
ivshmem-server, as it is also available via QEMU.

Preparing IVSHMEM server
************************
#. The ivshmem-server utility for QEMU can be found into the Zephyr SDK
   directory, in:
   ``/path/to/your/zephyr-sdk/zephyr-<version>/sysroots/x86_64-pokysdk-linux/usr/xilinx/bin/``

#. You may also find ivshmem-client utility, it can be useful to check if everything works
   as expected.

#. Run ivshmem-server. For the ivshmem-server, both number of vectors and
   shared memory size are decided at run-time (when the server is executed).
   For Zephyr, the number of vectors and shared memory size of ivshmem are
   decided at compile-time and run-time, respectively. For Arm64 we use
   vectors == 2 for the project configuration in this sample. Here is an example:

   .. code-block:: console

      # n = number of vectors
      $ sudo ivshmem-server -n 2
      $ *** Example code, do not use in production ***

#. Appropriately set ownership of ``/dev/shm/ivshmem`` and
   ``/tmp/ivshmem_socket`` for your deployment scenario. For instance:

   .. code-block:: console

      $ sudo chgrp $USER /dev/shm/ivshmem
      $ sudo chmod 060 /dev/shm/ivshmem
      $ sudo chgrp $USER /tmp/ivshmem_socket
      $ sudo chmod 060 /tmp/ivshmem_socket

Building and Running
********************

After getting QEMU ready to go, first create two output folders, so open two terminals
and create them, these folders will receive the output of Zephyr west commands:

   .. code-block:: console

      $ mkdir -p path/to/instance_1

On another terminal window do:

   .. code-block:: console

      $ mkdir -p path/to/instance_2

Then build the sample as follows, don't forget, two builds are necessary
to test this sample, so append the option ``-d path/to/instance_1`` and
on the other terminal window do the same, that is it ``-d path/to/instance_2``

.. zephyr-app-commands::
   :zephyr-app: samples/drivers/ipm/ipm_ivshmem
   :board: qemu_cortex_a53
   :goals: build
   :compact:

To run both QEMU sides, repeat the west build command followed
by ``-d path/to/instance_x`` where x is 1 or 2 depending on the
terminal window, using the run target:

.. zephyr-app-commands::
   :zephyr-app: samples/drivers/ipm/ipm_ivshmem
   :board: qemu_cortex_a53
   :goals: run
   :compact:

Expected output
***************

On the console just use the ``ivshmem_ipm_send`` command
followed by the destination peer-id, to get the peer-id destination
go to the other terminal window and check with ``ivshmem`` command:

   .. code-block:: console

      *** Booting Zephyr OS build zephyr-v3.4.0-974-g7fba7d395750 ***


      uart:~$ ivshmem
      IVshmem up and running:
         Shared memory: 0xafa00000 of size 4194304 bytes
         Peer id: 12
         Notification vectors: 2
      uart:~$

For example one of the instances has the peer-id 12, so go the other
instance and use the command to send the IPM notification followed
by this peer-id:

   .. code-block:: console

      *** Booting Zephyr OS build zephyr-v3.4.0-974-g7fba7d395750 ***


      uart:~$ ivshmem
      IVshmem up and running:
         Shared memory: 0xafa00000 of size 4194304 bytes
         Peer id: 11
         Notification vectors: 2
      uart:~$ ivshmem_ipm_send 12

Then go back to the other terminal window where user may see the reception
of the notification on the terminal:

   .. code-block:: console

      uart:~$ ivshmem
      IVshmem up and running:
         Shared memory: 0xafa00000 of size 4194304 bytes
         Peer id: 12
         Notification vectors: 2
      uart:~$ Received IPM notification over IVSHMEM