Re: [virtio-comment] Next VirtIO device for Project Stratos?

["Bradford, Robert" <robert.bradford@intel.com>]

On Tue, 2022-05-31 at 09:07 +0100, Alex BennÃe wrote:
> Watchdog / 35
> -------------
> 
> Discussion about this is usually conflated with reset functionality
> as
> the two are intimately related.
> 
> An early interest in this was for providing a well specified reset
> functionality firmware running on the -M virt machine model in QEMU.
> The
> need has been reduced somewhat with the provision of the sbsa-ref
> model
> which does have a defined reset pin.
> 
> Other questions that would need to be answered include how the
> functionality would interact with the hypervisor given a vCPU could
> easily not be scheduled by it and therefore miss its kick window.
> 

I guess this a risk with any use of a watchdog whether it be emulating
a physical device or a paravirtualised one. In practice we have never
seen this.

> Currently there have been no proposals for the spec or
> implementations.

I was the one who requested the ID be reserved. We have an
implementation in Cloud Hypervisor:
https://github.com/cloud-hypervisor/cloud-hypervisor/blob/main/virtio-devices/src/watchdog.rs

As well as the kernel side: 

https://github.com/cloud-hypervisor/linux/commit/cc8f7579faad79cdf02f9b6a742510cd1b1cf340

I admit writing up a patch for the specification fell through the
cracks. That's something I will try to rectify in the near future as it
would also be nice to be able to upstream the kernel patch.

Cheers,

Rob