Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 17 Apr 2019 09:51:47 -0700 | Subject | Re: EFI reboot vs. ACPI reboot (was: Re: [tip:x86/urgent] x86/reboot, efi: Use EFI reboot for Acer TravelMate X514-51T) | From | hpa@zytor ... |
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On April 17, 2019 9:37:29 AM PDT, Ingo Molnar <mingo@kernel.org> wrote: > >* hpa@zytor.com <hpa@zytor.com> wrote: > >> > 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. > >No, I still think "early" EFI is historically better with ACPI reboot. > >But can we find a firmware flag perhaps that will *not* result in EFI >reboot being turned off? > >> This, I believe, is known to not work. > >Yeah, I bet so. > >My problem is that the code appears to have the wrong assumptions: > > /* >* For most modern platforms the preferred method of powering off is via > * ACPI. However, there are some that are known to require the use of > * EFI runtime services and for which ACPI does not work at all. > * > * Using EFI is a last resort, to be used only if no other option > * exists. > */ > bool efi_reboot_required(void) > { > if (!acpi_gbl_reduced_hardware) > return false; > > efi_reboot_quirk_mode = EFI_RESET_WARM; > return true; > } > > >At minimum the comment is stale: "modern" platforms, *especially* when >the only bootup method is EFI, as in the ACER laptop case, I think the >preferred reboot method is absolutely an EFI reboot - and it's probably > >what Windows uses too. > >The question is, is acpi_gbl_reduced_hardware false on the Acer >TravelMate X514-51T? I think it has to be, for the quirk to make sense >- >if it's true then efi_reboot_required() would set the reboot method to >EFI. > >I.e. we seem to have a new category of systems that are advertising >themselves as 'full ACPI compliant', which are NOT old EFI systems, but > >modern EFI systems. > >Is there some good way to detect these - such as ACPI version or >something? > >Thanks, > > Ingo
That is exactly what the reduced hardware flag is supposed to indicate. As far as what Windows does, the are only two ways to find out: testing somehow, or these days Microsoft might actually answer if we ask nicely. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
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