> > >> That seems counter-intuitive to me: if no full ACPI hardware is > > >> implemented then we should assume reduced ACPI functionality, i.e. > > >> if > > >the > > >> EFI runtime is otherwise available we should default to it. > > > > > >It's a bit confusing, but my loose understanding is that previous > > >versions of the ACPI spec required system implementors to implement > > >the whole thing; but that's increasingly impractical today, e.g. with > > >ARM systems coming along, which do not gel well with some of the > > >historical x86-rooted design aspects that spilled over into ACPI. The > > >V5 spec introduces reduced mode as an opt-in new feature, but for > > >compatibility with pre-V5 implementations it needs to consider "full > > >hardware" mode as the default. > > > > > >> Feel free to send a patch that makes EFI reboot the default one > > >> under these circumstances, > > > > > >Just to check, you mean: EFI reboot (and shutdown) become the default > > >methods when the machine is booted in EFI mode, and EFI stuff has not > > >been disabled with a kernel parameter? > > >Even when running in full hardware ACPI mode. > > > > > >Thanks > > >Daniel > > > > This, I believe, is known to not work. > > It definitely used to be the case that EFI reboot was unreliable, but I don't know > the details. Sorry! Ard. I don't have the enough historical knowledge to state that EFI reboot is unreliable on most of the x86 systems but I did come across two systems that had buggy implementation of EFI reboot and hence I have added code to deal with EFI runtime services that cause page faults. I will ask around internally to check if it is a good idea to make EFI reboot the default method when the machine is booted in EFI mode. > I have added Sai to cc, he may be able to provide a bit more context > here, since he added the code to deal with page faults during EFI runtime service > invocations (which was inspired by a EFI reboot issue IIRC). That feature may > have improved the situation, but I am not confident at all that it fixes all > systems. I believe, the code I added should improve the situation but I am hesitant to say that it fixes *all* the systems because the code addresses only one type of bug namely EFI Reboot accessing illegal memory and I have no idea about other buggy implementations. Regards, Sai
