linux-kernel - Re: [PATCH 1/2] efi: Make 'efi_enabled' a function to query EFI facilities

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Date:	Mon, 21 Jan 2013 14:42:03 -0600
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matt Fleming <matt@...sole-pimps.org>
CC:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Tim Gardner <rtg.canonical@...il.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Olof Johansson <olof@...om.net>,
	Tony Luck <tony.luck@...el.com>,
	Steve Langasek <steve.langasek@...onical.com>,
	Colin Ian King <colin.king@...onical.com>,
	Matt Fleming <matt.fleming@...el.com>,
	David Airlie <airlied@...ux.ie>,
	Corentin Chary <corentincj@...aif.net>,
	Dave Jiang <dave.jiang@...el.com>,
	Peter Jones <pjones@...hat.com>,
	Konrad Rzeszutek Wilk <konrad@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] efi: Make 'efi_enabled' a function to query EFI facilities

On 01/21/2013 02:40 PM, Matt Fleming wrote:
> From: Matt Fleming <matt.fleming@...el.com>
> 
> Originally 'efi_enabled' indicated whether a kernel was booted from
> EFI firmware. Over time its semantics have changed, and it now
> indicates whether or not we are booted on an EFI machine with
> bit-native firmware, e.g. 64-bit kernel with 64-bit firmware.
> 
> But users actually want to query 'efi_enabled' for different reasons -
> what they really want access to is the list of available EFI
> facilities.
> 
> For instance, the x86 reboot code needs to know whether it can invoke
> the ResetSystem() function provided by the EFI runtime services, while
> the ACPI OSL code wants to know whether the EFI config tables were
> mapped successfully. There are also checks in some of the platform
> driver code to simply see if they're running on an EFI machine (which
> would make it a bad idea to do BIOS-y things).
> 

Could you please explain as part of the checkin comment why this is
needed for urgent/stable?  I.e. what breaks *now*, as opposed to this
being a cleanup for the next merge window.

	-hpa


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