Refine kernel requirements for UEFI boot

[David Bryant]

The current instructions in BLFS chapter 5 (Using GRUB to Set Up the Boot Process with UEFI) contend that some unnecessary kernel configuration options are actually needed. Specifically:

CONFIG_PARTITION_ADVANCED is not necessary CONFIG_SYSFB_SIMPLEFB is not necessary CONFIG_EFI_RUNTIME_MAP no longer exists (kernel 5.19.8) CONFIG_SIMPLEDRM no longer exists, either

I can't find a new name for CONFIG_EFI_RUNTIME_MAP. I do see "CONFIG_EFI_RUNTIME_WRAPPERS=y" in my .config file. But I can't find it in the menu, to try to turn it off. Not certain what's up with that.

I do have CONFIG_EFI_FB=y which, I think, has supplanted CONFIG_SIMPLEDRM. This option appears under "Support for framebuffer devices --->". I also have CONFIG_MS_DOS=y and CONFIG_VFAT_FS=y (under File Systems --->), but I don't think those are relevant ... the EFI firmware understands VFAT well enough to load grubx64.efi from the hard disk.

I have made the changes in "grub-setup.xml", and I have verified that it renders nicely. The full path to the attached file in the BLFS repo is postlfs/filesystems/uefi-bootloaders/grub.setup.xml.

[David Bryant]

Modified grub-setup.xml

[Xi Ruoyao]

CONFIG_SIMPLEDRM is a typo, it should be CONFIG_DRM_SIMPLEDRM and I'll fix it.

$ grep CONFIG_EFI_RUNTIME_MAP /boot/config-5.19.8
CONFIG_EFI_RUNTIME_MAP=y

We deliberately use CONFIG_SYSFB_SIMPLEFB and CONFIG_DRM_SIMPLEDRM instead of CONFIG_EFI_FB. The kernel developers consider CONFIG_EFI_FB (and everything under CONFIG_FB but not itself) legacy.

If you don't select CONFIG_PARTITION_ADVANCED, then CONFIG_EFI_PARTITION is enabled by default. But we can't tell everyone not to select CONFIG_PARTITION_ADVANCED, as somebody may need it. So we explicitly selects CONFIG_EFI_PARTITION here.

[Xi Ruoyao]

Typo fixed at r11.2-142-g9c44927210. Closing.

[Xi Ruoyao]

Perhaps CONFIG_EFI_RUNTIME_MAP is not needed because it looks like a debug option. And I just copied it from the old grub-efi hint.

I'll test to remove it.

[Xi Ruoyao]

Replying to 17085:

I also have CONFIG_MS_DOS=y and CONFIG_VFAT_FS=y (under File Systems --->), but I don't think those are relevant ... the EFI firmware understands VFAT well enough to load grubx64.efi from the hard disk.

It's not possible to mount /boot/efi without CONFIG_VFAT_FS. It can be y/M, but not n.

[Xi Ruoyao]

CONFIG_EFI_RUNTIME_MAP removed at r11.2-143-g27329c077d, and CONFIG_VFAT_FS added at r11.2-144-g7027897a70.

[David Bryant]

Thank you for clarifying the kernel configuraton options. But what about all the corrections to grammar, idiom, and punctuation?

[pierre]

Replying to David Bryant:

Thank you for clarifying the kernel configuraton options. But what about all the corrections to grammar, idiom, and punctuation?

Reading this ticket and its comments, I cannot figure out where you mentioned them. I guess the reason is you sent the full file grub-setup.xml, so it is not evident to see that there are also grammar, idiom, and punctuation fixes. It's much better to send a patch (using git diff), so that it is easy to see what is changed.

I'll try to update the book with your changes.

[pierre]

Done at c8391c3d85. This may need reviewing again...