Looking for help and advice on using RPMSG-over-VIRTIO

Looking for help and advice on using RPMSG-over-VIRTIO

[Doug Miller]

I am working on adding SR-IOV for a new adapter and need to find a way
to communicate between guest and host drivers without using the adapter
hardware. I have been looking at RPMSG-over-VIRTIO as a way to this, but
have not been able to figure out how the host would setup the RPMSG
device needed for this.

I have seen at least one bug in virtio_rpmsg_bus that was discovered and
fixed by qemu developers, and so am hoping there may be some experience
with rpmsg here that can help.

I see an example in the Linux kernel for using rpmsg from the guest
(client) side, in samples/rpmsg/rpmsg_client_sample.c. What I'm having
difficulty with is finding examples or documentation on how to do the
host side. I have heard that the VMMs may also play a role in setting
this up, or are doing something similar, but so far I am not able to
find code examples in qemu or libvert.

Any help would be appreciated,
Doug

External recipient

Re: Looking for help and advice on using RPMSG-over-VIRTIO

[Doug Miller]

On 9/19/2024 7:26 AM, Doug Miller wrote:
> I am working on adding SR-IOV for a new adapter and need to find a way
> to communicate between guest and host drivers without using the
> adapter hardware. I have been looking at RPMSG-over-VIRTIO as a way to
> this, but have not been able to figure out how the host would setup
> the RPMSG device needed for this.
>
> I have seen at least one bug in virtio_rpmsg_bus that was discovered
> and fixed by qemu developers, and so am hoping there may be some
> experience with rpmsg here that can help.
>
> I see an example in the Linux kernel for using rpmsg from the guest
> (client) side, in samples/rpmsg/rpmsg_client_sample.c. What I'm having
> difficulty with is finding examples or documentation on how to do the
> host side. I have heard that the VMMs may also play a role in setting
> this up, or are doing something similar, but so far I am not able to
> find code examples in qemu or libvert.
>
> Any help would be appreciated,
> Doug
>
I see a comment in drivers/pci/controller/pci-hyperv.c that describes
what I'm looking, but what I need must work for any (independently of)
hypervisor/VMM.

"Hyper-V SR-IOV provides a backchannel mechanism in software for
communication between a VF driver and a PF driver..."

It certainly seems like rpmsg-over-virtio would accomplish this, but
even some other facility that is VMM-independent would be fine. I'm
looking for any sort of solution that does not require (major)
modification of the kernel. Can anyone state authoritatively that
rpmsg-over-virtio is not capable of this? Is there something like this
backchannel offered in the linux kernel? Is there something else that
can be used to accomplish this PF-VF communication using existing kernel
facilities?

External recipient