Bug 1118949

Summary:	32bit UEFI can't boot x86_64 kernel because of missing CONFIG_EFI_MIXED
Product:	[Fedora] Fedora	Reporter:	Lars S. Jensen <lars.s.jensen>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED RAWHIDE	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	rawhide	CC:	8ru2u4gz, gansalmon, gdt, itamar, jonathan, kernel-maint, madhu.chinakonda, mchehab, mikhail.v.gavrilov, pjones, vorona.tolik
Target Milestone:	---	Keywords:	FutureFeature, Triaged
Target Release:	---
Hardware:	x86_64
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-05-16 12:38:24 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Lars S. Jensen 2014-07-12 08:05:55 UTC

Description of problem:
Many of the first generation Baytrail/Atom tablet only have UEFI32.
To boot a x86_64 kernel/Fedora from UEFI32 require kernel config parameter CONFIG_EFI_MIXED that was included from version kernel 3.15.x.
I am currenly using an Arch dist to test 64bit kernel that have the CONFIG_EFI_MIXED parameter.

Version-Release number of selected component (if applicable):
kernel-core-3.16.0-0.rc4.git2.1.fc21.x86_64
kernel-core-3.16.0-0.rc4.git2.1.fc22.x86_64

How reproducible:
Check /boot/config for CONFIG_EFI_MIXED.

Steps to Reproduce:
1. Rawhide and Fedora21
grep EFI_MIXED /boot/config-3.16.0-0.rc4.git*

Actual results:
# CONFIG_EFI_MIXED is not set

Expected results:
CONFIG_EFI_MIXED=y

Additional info:
The support of Baytrail/Atom tablet is commimg in kernel 3.16-3.17 and should be tested before release of F21:-).
If also require a grub32 boot loader image in /boot/EFI/...
This is bug #746421 that can be reopened.

Comment 1 Josh Boyer 2014-07-12 14:02:16 UTC

The official policy is that Fedora doesn't support 32-bit UEFI.  I believe we need more than just that option enabled in the kernel to properly support this.  I've CC'd the grub maintainer to see what the plans around that are.

Comment 2 Lars S. Jensen 2014-07-12 14:56:53 UTC

The current grub2-efi-2.02-0.6.fc21.i686 should able to boot the kernel because it is a 32-bit UEFI bootloader and it start without any problems on my UEFI32 baytrail tablet. It only need to be install :-). 

The grub-efi.i686 and grub-modules-modules.i686 binary can be install in parallel with x86_64 version because it use differne naming scheme: ...x64,x86_64-efi and ...ia32/i386-efi.
There is some grub commen files that may needs to be moved/fixed.

Comment 3 Josh Boyer 2014-11-06 00:09:24 UTC

We aren't going to change this for F21.  We'll move the bug to rawhide and work out whether this is something we're going to support in F22.

Comment 4 Lars S. Jensen 2014-12-30 10:42:57 UTC

I am now using F21 x86_64 system and fedora's F22 kernel with Adam's Fedlet kernel patchs for Baytrail and CONFIG_EFI_MIXED. 
The current rpm grub2-efi.i686 don't includes the grub command-module: linux/initd that are needed instead of linuxefi/initdefi to boot 64-bit "efi" kernel from UEFI 32-bit. But the grub image with linux/initd can be created from grub2-efi-modules.i686 with grub2-mkimage.

Comment 5 Lars S. Jensen 2015-04-10 09:17:56 UTC

I will build/test the f22/rawhide kernel after the CONFIG_EFI_MIXED was added to it's git repo yesterday :-)

Comment 6 Mikhail 2015-06-03 12:57:14 UTC

Don't understand how boot Fedora 22 on Bay Trail tablet :(

Comment 7 Mikhail 2016-05-14 06:19:03 UTC

A year has passed now Fedora 24, but support UEFI 32 still have not been added.

Comment 8 Josh Boyer 2016-05-16 12:38:24 UTC

(In reply to Mikhail from comment #7)
> A year has passed now Fedora 24, but support UEFI 32 still have not been
> added.

commit f0d73f97ac8e929de523c4a232620e4b42571011
Author: Peter Jones <pjones>
Date:   Thu Apr 9 10:24:01 2015 -0400

    Enable CONFIG_EFI_MIXED.
    
    This enables the 32-bit EFI entry point on 64-bit kernels, so hardware
    like Baytrail devices with 32-bit firmware on a 64-bit cpu can boot the
    64-bit kernel.
    
    Signed-off-by: Peter Jones <pjones>


It was enabled a year ago in our kernels.  If it isn't working, it's because of grub or something else.