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

  1. 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/

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

  3. 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 ***

  4. 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

See also

IPM Interface