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

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Message-ID: <0fac8c71-6f18-d15c-23f5-075dbc45f3f9@igalia.com>
Date:   Mon, 23 May 2022 11:56:12 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Scott Branden <scott.branden@...adcom.com>,
        Petr Mladek <pmladek@...e.com>,
        Sebastian Reichel <sre@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Desmond yan <desmond.yan@...adcom.com>
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        Julius Werner <jwerner@...omium.org>,
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        zhenwei pi <pizhenwei@...edance.com>
Subject: Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list

On 19/05/2022 16:20, Scott Branden wrote:
> [...] 
>> 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.
>>
>> [...]
>> 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.
>>
>> 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