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diff --git a/Documentation/arch/x86/x86_64/uefi.rst b/Documentation/arch/x86/x86_64/uefi.rst new file mode 100644 index 000000000000..e84592dbd6c1 --- /dev/null +++ b/Documentation/arch/x86/x86_64/uefi.rst @@ -0,0 +1,75 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +General note on [U]EFI x86_64 support +===================================== + +The nomenclature EFI and UEFI are used interchangeably in this document. + +Although the tools below are _not_ needed for building the kernel, +the needed bootloader support and associated tools for x86_64 platforms +with EFI firmware and specifications are listed below. + +1. UEFI specification: http://www.uefi.org + +2. Booting Linux kernel on UEFI x86_64 platform can either be + done using the <Documentation/admin-guide/efi-stub.rst> or using a + separate bootloader. + +3. x86_64 platform with EFI/UEFI firmware. + +Mechanics +--------- + +Refer to <Documentation/admin-guide/efi-stub.rst> to learn how to use the EFI stub. + +Below are general EFI setup guidelines on the x86_64 platform, +regardless of whether you use the EFI stub or a separate bootloader. + +- Build the kernel with the following configuration:: + + CONFIG_FB_EFI=y + CONFIG_FRAMEBUFFER_CONSOLE=y + + If EFI runtime services are expected, the following configuration should + be selected:: + + CONFIG_EFI=y + CONFIG_EFIVAR_FS=y or m # optional + +- Create a VFAT partition on the disk with the EFI System flag + You can do this with fdisk with the following commands: + + 1. g - initialize a GPT partition table + 2. n - create a new partition + 3. t - change the partition type to "EFI System" (number 1) + 4. w - write and save the changes + + Afterwards, initialize the VFAT filesystem by running mkfs:: + + mkfs.fat /dev/<your-partition> + +- Copy the boot files to the VFAT partition: + If you use the EFI stub method, the kernel acts also as an EFI executable. + + You can just copy the bzImage to the EFI/boot/bootx64.efi path on the partition + so that it will automatically get booted, see the <Documentation/admin-guide/efi-stub.rst> page + for additional instructions regarding passage of kernel parameters and initramfs. + + If you use a custom bootloader, refer to the relevant documentation for help on this part. + +- If some or all EFI runtime services don't work, you can try following + kernel command line parameters to turn off some or all EFI runtime + services. + + noefi + turn off all EFI runtime services + reboot_type=k + turn off EFI reboot runtime service + +- If the EFI memory map has additional entries not in the E820 map, + you can include those entries in the kernels memory map of available + physical RAM by using the following kernel command line parameter. + + add_efi_memmap + include EFI memory map of available physical RAM |