1.. SPDX-License-Identifier: GPL-2.0
2
3=====================================
4General note on [U]EFI x86_64 support
5=====================================
6
7The nomenclature EFI and UEFI are used interchangeably in this document.
8
9Although the tools below are _not_ needed for building the kernel,
10the needed bootloader support and associated tools for x86_64 platforms
11with EFI firmware and specifications are listed below.
12
131. UEFI specification:  http://www.uefi.org
14
152. Booting Linux kernel on UEFI x86_64 platform requires bootloader
16   support. Elilo with x86_64 support can be used.
17
183. x86_64 platform with EFI/UEFI firmware.
19
20Mechanics
21---------
22
23- Build the kernel with the following configuration::
24
25	CONFIG_FB_EFI=y
26	CONFIG_FRAMEBUFFER_CONSOLE=y
27
28  If EFI runtime services are expected, the following configuration should
29  be selected::
30
31	CONFIG_EFI=y
32	CONFIG_EFI_VARS=y or m		# optional
33
34- Create a VFAT partition on the disk
35- Copy the following to the VFAT partition:
36
37	elilo bootloader with x86_64 support, elilo configuration file,
38	kernel image built in first step and corresponding
39	initrd. Instructions on building elilo	and its dependencies
40	can be found in the elilo sourceforge project.
41
42- Boot to EFI shell and invoke elilo choosing the kernel image built
43  in first step.
44- If some or all EFI runtime services don't work, you can try following
45  kernel command line parameters to turn off some or all EFI runtime
46  services.
47
48	noefi
49		turn off all EFI runtime services
50	reboot_type=k
51		turn off EFI reboot runtime service
52
53- If the EFI memory map has additional entries not in the E820 map,
54  you can include those entries in the kernels memory map of available
55  physical RAM by using the following kernel command line parameter.
56
57	add_efi_memmap
58		include EFI memory map of available physical RAM
59