Re: [VirtIO] Support for various devices in Xen

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Hi Andrei,

Great that you are working with Xen and virtio. We at AMD are very
interested in it as well.

I'll let Artem (CCed) and his team comment about the xen-troops
repository.

I can share that from our side we are working toward adding complete
support for using QEMU as virtio-backends provider. Vikram (CCed)
managed to get virtio-net to work with the backend in QEMU. He should be
able to provide instructions. We want to get those patches upstream in
Xen and QEMU as soon as possible.

The libxl changes are lagging behind a bit and you might have to use
device_model_args to enable virtio backends in QEMU.

For SCMI, I'll let Bertrand (CCed) comment.

Cheers,

Stefano


On Thu, 11 Jan 2024, Andrei Cherechesu (OSS) wrote:
> Hello,
> 
> As I've mentioned in previous discussion threads in the xen-devel
> community, we are running Xen 4.17 (uprev to 4.18 in progress) on NXP
> S32G automotive processors (Cortex-A53 cores) and we wanted to know more
> about the support for various VirtIO device types in Xen.
> 
> In the Xen 4.17 release notes, the VirtIO standalone backends mentioned
> as supported and tested are: virtio-disk, virtio-net, virtio-i2c and
> virtio-gpio.
> 
> However, we've only managed to successfully set up and try some
> use-cases with the virtio-disk standalone backend [0] (which Olexandr
> provided) based on the virtio-mmio transport.
> 
> As such, we have a few questions, which we haven't been able to figure
> out from the mailing list discussions and/or code:
>     1. Are there any plans for the virtio-disk repo to have a stable
>     version? Is it going to be long-term hosted and maintained in the
>     xen-troops github repo? Or was it just an one-time PoC implementation
> 
>     and the strategy for future VirtIO devices will be based on a more generic
> 
>     approach (i.e., without need for a specific standalone app)?
> 
> 
>     2. With regards to the other backends, we want to try out and provide PV
> 
>     networking to a DomU based on virtio-net, but we haven't found any 
> available
> 
>     resources for it (e.g., the standalone backend implementation if needed 
> for
> 
>     control plane, configuration examples, presentations, demos, docs). Does 
> it
> 
>     rely on the QEMU virtio-net or vhost implementation? Are there any 
> examples
> 
>     on how to set it up? Any required Xen/Linux Kernel/QEMU versions?
> 
> 
>     3. What other VirtIO device types are there planned to be supported in 
> Xen?
> 
>     I'm supposing libxl will also need changes to accomodate new configuration
> 
>     parameters for each of them. Or is there something I'm missing?
> 
> 
>     4. Also, while we're at it, are there any plans regarding SCMI
>     awareness for Xen (e.g., SCMI Mediator - where the RFC thread from 2022
> 
>     seems discontinued)? Or is the preferred approach for sharing SCMI access
> 
>     to guests through virtio-scmi?
> 
> Thank you very much for the support, once again, and we're also looking
> forward to the progress on the rust-vmm initiative.
> 
> Regards,
> Andrei Cherechesu,
> NXP Semiconductors
> 
> [0] https://github.com/xen-troops/virtio-disk
> 
> 
>