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

["Alex Bennée" <alex.bennee@linaro.org>]

"Bradford, Robert" <robert.bradford@intel.com> writes:

> On Tue, 2022-05-31 at 09:07 +0100, Alex Bennée 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
>

Ahh good. I guess it could be another cloud hypervisor component that
makes the transition to rust-vmm if there is interest?

> 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.

Thanks, please feel free to Cc me on any such patches and we can take a
look.

-- 
Alex Bennée

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