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):
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*
# CONFIG_EFI_MIXED is not set
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.
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.
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.
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.
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.
I will build/test the f22/rawhide kernel after the CONFIG_EFI_MIXED was added to it's git repo yesterday :-)
Don't understand how boot Fedora 22 on Bay Trail tablet :(
A year has passed now Fedora 24, but support UEFI 32 still have not been added.
(In reply to Mikhail from comment #7)
> A year has passed now Fedora 24, but support UEFI 32 still have not been
Author: Peter Jones <firstname.lastname@example.org>
Date: Thu Apr 9 10:24:01 2015 -0400
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
Signed-off-by: Peter Jones <email@example.com>
It was enabled a year ago in our kernels. If it isn't working, it's because of grub or something else.