UEFI, Grub, Ubuntu

[atanamir]

Hello everyone,

I'm pretty exasperated by this problem, so I figure I'll ask for some help here. I'm trying to do some work using UEFI -- namely, I'd like to view/change the runtime variables that UEFI exposes. However, to do this, I need to get Linux to boot with UEFI first.

I've gotten some success; on one machine everything works beautifully -- grub-efi loads, the kernel is selected, and the system boots up nicely. However, on another system, immediately after the kernel is selected (and the initrd image is loaded and control is passed over to the kernel) the system hangs at a black screen. Numlock, etc. all do not respond.

What would be a way to start trying to debug what went wrong? Since i have no output whatsoever on the screen thus far, how can I determine whether or not it's a grub problem or a kernel problem?

Note that the exact same grub config and kernel etc. boot up fine on one machine, but not this one.

Thanks!

[yancek]

Since i have no output whatsoever on the screen thus fa

Are you saying you see no output when you hit the ESC key during Grub boot? That would be very unusual!
What is the difference in hardware between the two machines?

[atanamir]

Grub itself is fine -- I see the grub menu, I can access the grub prompt, etc. However, after grub when the kernel is about to kick in -- that's when the blank screen + hang occurs.

The difference in the two machines is primarily the chipset (P55 vs. X5, and the BIOS (one is an Intel BIOS, the other one is an AMI BIOS which appears to have better EFI support).

I've tried the following kernel flags in different combinations:
debug=all, loglevel=7, acpi=force, agp=off, video=vesafb, video=uvesafb, video=efifb, vga=771, earlyprintk=vga

The only one that makes a difference is 'noefi', which allows the system to boot normally. However, the EFI stuff are all disabled, which is exactly what I need to use. This leads me to believe that it's not a grub problem, but a kernel problem. I'd like to see some sort of panic on the screen or something though from which to debug.