Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list

On 19/05/2022 16:20, Scott Branden wrote:

[...] 

quoted

Hi Scott / Desmond, thanks for the detailed answer! Is this adapter
designed to run in x86 only or you have other architectures' use cases?

The adapter may be used in any PCIe design that supports DMA.
So it may be possible to run in arm64 servers.

quoted

[...]
With that said, and given this is a lightweight notifier that ideally
should run ASAP, I'd keep this one in the hypervisor list. We can
"adjust" the semantic of this list to include lightweight notifiers that
reset adapters.

Sounds the best to keep system operating as tested today.

quoted

With that said, Petr has a point - not always such list is going to be
called before kdump. So, that makes me think in another idea: what if we
have another list, but not on panic path, but instead in the custom
crash_shutdown()? Drivers could add callbacks there that must execute
before kexec/kdump, no matter what.

It may be beneficial for some other drivers but for our use we would 
then need to register for the panic path and the crash_shutdown path. 
We notify the VK card for 2 purposes: one to stop DMA so memory stop 
changing during a kdump.  And also to get the card into a good state so 
resets happen cleanly.

Thanks Scott! With that, I guess it's really better to keep this
notifier in this hypervisor/early list - I'm planning to do that for V2.
Unless Petr or somebody has strong feelings against that, of course.

Cheers,


Guilherme