Re: [PATCH 0/6] Add ivshmem-flat device

[Markus Armbruster <armbru@redhat.com>]

Gustavo Romero <gustavo.romero@linaro.org> writes:

[...]

> This patchset introduces a new device, ivshmem-flat, which is similar to the
> current ivshmem device but does not require a PCI bus. It implements the ivshmem
> status and control registers as MMRs and the shared memory as a directly
> accessible memory region in the VM memory layout. It's meant to be used on
> machines like those with Cortex-M MCUs, which usually lack a PCI bus, e.g.,
> lm3s6965evb and mps2-an385. Additionally, it has the benefit of requiring a tiny
> 'device driver,' which is helpful on some RTOSes, like Zephyr, that run on
> memory-constrained resource targets.
>
> The patchset includes a QTest for the ivshmem-flat device, however, it's also
> possible to experiment with it in two ways:
>
> (a) using two Cortex-M VMs running Zephyr; or
> (b) using one aarch64 VM running Linux with the ivshmem PCI device and another
>     arm (Cortex-M) VM running Zephyr with the new ivshmem-flat device.
>
> Please note that for running the ivshmem-flat QTests the following patch, which
> is not committed to the tree yet, must be applied:
>
> https://lists.nongnu.org/archive/html/qemu-devel/2023-11/msg03176.html

What problem are you trying to solve with ivshmem?

Shared memory is not a solution to any communication problem, it's
merely a building block for building such solutions: you invariably have
to layer some protocol on top.  What do you intend to put on top of
ivshmem?

[...]