Kernel doesn't support EFI handover

[NTULINUX]

error: ../../grub-core/loader/i386/efi/linux.c:267:kernel dosen't support EFI handover.
error: ../../gurb-core/loader/i386/efi/linux.c:94:you need to load the kernel first.

Some people(Ubuntu) claim that this is a bug. I don't know if we can make a corresponding patch for this, which can be applied to Ubuntu 20.10 and CentOS 8, PREEMPT_RT works well on CentOS 8 and Ubuntu 20.10

I use eufi to start Grub2, with 4.19.152 kernel and IPIPE patch

Originally posted by @obrire in #9 (comment)

[NTULINUX]

Using EFI instead of legacy/CSM may cause latency spikes so it has been disabled in Kconfig.

If you want to test it, you can modify the option for EFI in Kconfig and remove the "&& !IPIPE" here:

https://github.com/NTULINUX/RTAI/blob/master/ksrc/v4.19.152/0003-Countless-Kconfig-tweaks-for-IPIPE.patch#L348

File: arch/x86/Kconfig

And rebuild the kernel. This configuration is not supported and may not even boot with IPIPE enabled. PREEMPT_RT disables EFI by default, you need to specify efi=runtime on the kernel parameters.

Related commits:

https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit?&id=27a9777fdc514fd1ca658421fba0cb1746837e82

https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit?&id=70d131f473e99dc33db7c01994f72d4bded63e29

I have played with PREEMPT_RT on EFI platforms and some boards have terrible latency with it, while others are fine.

If you don't have any problems, please post your dmesg output on the EFI-enabled RTAI kernel.

Thank you!