Re: [VirtIO] Support for various devices in Xen

[Viresh Kumar <viresh.kumar@xxxxxxxxxx>]

+ Few Linaro folks.

Hi Andrei,

On 11-01-24, 15:32, 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.

We worked on I2C and GPIO for Linaro's Project Orko [1].

> 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.

We have tested our work mostly with the rust-vmm community. We have
already upstreamed support for Xen's Foreign and Grant mapping in
there. We are maintaining a separate crate [2] inside of rust-vmm, for
all the backends, which can also be tested easily with Xen I suppose
(now that we have support for a generic Virtio-device in there).

> Regards,
> Andrei Cherechesu,
> NXP Semiconductors
> 
> [0] https://github.com/xen-troops/virtio-disk

-- 
viresh

[1] https://linaro.atlassian.net/wiki/spaces/ORKO/overview
[2] https://github.com/rust-vmm/vhost-device