Messages in this thread | | | From | Ard Biesheuvel <> | Date | Wed, 2 Feb 2022 15:01:37 +0100 | Subject | Re: [PATCH v2] arm64: move efi_reboot to restart handler |
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On Wed, 2 Feb 2022 at 13:41, Krzysztof Adamski <krzysztof.adamski@nokia.com> wrote: > > Dnia Tue, Feb 01, 2022 at 01:58:29PM +0000, Mark Rutland napisał(a): > >> If we use the restart handlers only to reset the system, this is indeed > >> true. But technically, restart handlers support the scenario where the > >> handler does some action that does not do reset of the whole system and > >> passes the control further down the chain, eventually reaching a handler > >> that will reset the whole system. > >> This can be done on non-uefi systems without problems but it doesn't > >> work on UEFI bases arm64 systems and this is a problem for us. > >> > >> In other words, I would like to be able to run a restart handler on EFI > >> based ARM64 systems, just like I can on other systems, just for its > >> "side effects", not to do the actual reboot. Current code disables this > >> possibility on an ARM64 EFI system. > > > >It sounds like two things are being conflated here: > > > >1) A *notification* that a restart will subsequently occur. > >2) A *request* to initiate a restart. > > > >IIUC (1) is supposed to be handled by the existing reboot notifier mechanism > >(see the reboot_notifier_list) which *is* invoked prior to the EFI reboot > >today. > > > >IMO, using restart handlers as notifiers is an abuse of the interface, and > >that's the fundamental problem. > > > >What am I missing? > > You are completly right. It is possible that I would like to be able to > *abuse* the restart handlers as notifier. You are right that we have a > reboot_notifier but it is not good enough for my usecase - it is only > called, well, on reboot. It is not called in case of emergency_restart() > so in case of a panic, this won't happen. It also is called much earlier > than restart handlers which also makes a difference in some cases. So I > see no other choice than to abuse the restart_handler mechanism for that. >
Why would such a platform implement ResetSystem() in the first place if it cannot be used?
So the right solution here is for the firmware to publish a EFI_RT_PROPERTIES_TABLE that describes ResetSystem() as unsupported, and Linux will happily disregard it and try something else.
Btw please cc linux-efi@vger.kernel.org and myself on future EFI issues. I found this thread by accident.
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