linux-kernel - Re: [PATCH v2] arm64: move efi

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Message-ID: <79bcce92-abb2-4c3e-7193-d18e144da8a0@nokia.com>
Date:   Tue, 15 Feb 2022 09:44:27 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Matija Glavinic-Pecotic <matija.glavinic-pecotic.ext@...ia.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Krzysztof Adamski <krzysztof.adamski@...ia.com>,
        linux-efi@...r.kernel.org
Subject: Re: [PATCH v2] arm64: move efi_reboot to restart handler

Hello Mark, Ard,

On 01/02/2022 14:58, Mark Rutland wrote:
>> You could argue that restart handlers were not created for that but they
>> suit this purpose ideally and it wouldn't make much sense (in my
>> opinion) to add yet another notifier chain that would run before reset
>> notifiers, for code that is not supposed to reset the whole system and
>> this is exacly what I would have to do if efi_reboot() is forced to be
>> called before all handlers.
> 
> As above, I think that's just using the wrong interface, and the reboot
> notifier mechanism *already* exists, so I'm really confused here.
> 
> Have I misunderstood what you're trying to achieve?
> 
> Is there some problem with the reboot notifier mechanism that I am unaware of?
> e.g. do we bypass them in some case where you think they're needed?
> 
> Are you simply unaware of reboot notifiers?

Could you please check the simple case of pwrseq_emmc.c?

While that's currently the only example of this kind upstream I can imagine
further use-cases, especially in storage area like above.

Would you suggest it's illegal usage of register_restart_handler()?
Do we need to fix pwrseq_emmc.c by introducing new atomic notifier chain
which will be called before restart handlers, so that it works on
emergency_restart()?

-- 
Best regards,
Alexander Sverdlin.