IPM over IVSHMEM

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:
```
# 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:

$ 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:

$ mkdir -p path/to/instance_1

On another terminal window do:

$ 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

west build -b qemu_cortex_a53 samples/drivers/ipm/ipm_ivshmem

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:

west build -b qemu_cortex_a53 samples/drivers/ipm/ipm_ivshmem
west build -t run

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:

*** 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:

*** 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:

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