linux-kernel - Re: EFI reboot vs. ACPI reboot (was: Re: [tip:x86/urgent] x86/reboot, efi: Use EFI reboot for Acer TravelMate X514-51T)

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Date:   Tue, 16 Apr 2019 19:35:18 +0800
From:   Daniel Drake <drake@...lessm.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jian-Hong Pan <jian-hong@...lessm.com>,
        matt@...eblueprint.co.uk,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>, hpa@...or.com,
        linux-efi@...r.kernel.org, Len Brown <len.brown@...el.com>,
        linux-tip-commits@...r.kernel.org,
        Endless Linux Upstreaming Team <linux@...lessm.com>
Subject: Re: EFI reboot vs. ACPI reboot (was: Re: [tip:x86/urgent] x86/reboot,
 efi: Use EFI reboot for Acer TravelMate X514-51T)

On Tue, Apr 16, 2019 at 4:20 PM Ingo Molnar <mingo@...nel.org> wrote:
> I wanted to get a second opinion from the EFI folks for this whole
> concept. On x86 we default to ACPI reboot on modern systems, and we
> default to EFI reboot on modern EFI systems, via the
> efi_reboot_required() method which keys off on acpi_gbl_reduced_hardware
> to create a barrier for older ACPI systems.

So if acpi_gbl_reduced_hardware is set, we are on a "modern EFI
system", and EFI reboot is used.

> It appears that Acer TravelMate X514-51T systems get marked as
> 'acpi_gbl_reduced_hardware' which enables ACPI-reboot, but they require
> EFI-reboot.

We will double check, but in this case I believe the system is *not*
marked as reduced hardware, which is why ACPI reboot is used.

> Should we perhaps re-think the boundary between EFI-reboot and
> ACPI-reboot systems? I.e. if the EFI runtime is enabled, shouldn't we
> just use the EFI reboot method?

I agree this is a good question.

We also previously hit a similar issue for shutdown on Acer laptops
which is still unresolved.
https://marc.info/?l=linux-acpi&m=148857214431346&w=2

Daniel