From: Ingo Molnar <mingo@kernel.org>
To: hpa@zytor.com
Cc: Daniel Drake <drake@endlessm.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jian-Hong Pan <jian-hong@endlessm.com>,
matt@codeblueprint.co.uk,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
linux-efi@vger.kernel.org, Len Brown <len.brown@intel.com>,
linux-tip-commits@vger.kernel.org,
Endless Linux Upstreaming Team <linux@endlessm.com>
Subject: Re: EFI reboot vs. ACPI reboot (was: Re: [tip:x86/urgent] x86/reboot, efi: Use EFI reboot for Acer TravelMate X514-51T)
Date: Wed, 17 Apr 2019 18:37:29 +0200 [thread overview]
Message-ID: <20190417163729.GA53511@gmail.com> (raw)
In-Reply-To: <17516564-37AC-4F77-9C0D-0DD71F8045EA@zytor.com>
* 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
next prev parent reply other threads:[~2019-04-17 16:37 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-12 8:01 [PATCH v2] x86/reboot: Use efi reboot for Acer TravelMate X514-51T Jian-Hong Pan
2019-04-16 7:52 ` [tip:x86/urgent] x86/reboot: Use EFI " tip-bot for Jian-Hong Pan
2019-04-16 8:07 ` [tip:x86/urgent] x86/reboot, efi: " tip-bot for Jian-Hong Pan
2019-04-16 8:20 ` EFI reboot vs. ACPI reboot (was: Re: [tip:x86/urgent] x86/reboot, efi: Use EFI reboot for Acer TravelMate X514-51T) Ingo Molnar
2019-04-16 11:35 ` Daniel Drake
2019-04-17 6:16 ` Ingo Molnar
2019-04-17 12:38 ` Daniel Drake
2019-04-17 15:15 ` hpa
2019-04-17 15:45 ` Ard Biesheuvel
2019-04-17 17:22 ` Prakhya, Sai Praneeth
2019-04-17 18:23 ` Ingo Molnar
2019-04-17 19:07 ` Ard Biesheuvel
2019-04-17 19:17 ` Ingo Molnar
2019-04-17 16:37 ` Ingo Molnar [this message]
2019-04-17 16:51 ` hpa
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