kexec --real-mode

[Eric W. Biederman]

Bernhard Walle <bwalle at suse.de> writes:

> * Eric W. Biederman [2008-04-28 10:55]:
>> 
>> It is a different code path.  It is designed to exercise the 16bit BIOS
>> calls that the kernel uses with a lot of serial port debugging
>> so we can see if that is the problem.
>
> Well, that gives me 
> ------------------------------------------------------------
> I'm in purgatory
> kexec_test 20080324 starting...
> eax: 00000000 ebx: 00000000 ecx: 00000000 edx: 00000000
> esi: 00000000 edi: 00000000 esp: 00008FF8 ebp: 00000000
> idt: 00000000 00000000
> gdt: 0000006F 00005BA0
> Switching descriptors.
> Descriptors changed.
> Legacy pic setup.
> In real mode.
> Interrupts enabled.
> Base memory size: 0276
> A20 disabled.
> E820 Memory Map.
> 000000000009D800 @ 0000000000000000 type: 00000001
> 0000000000002800 @ 000
> ------------------------------------------------------------
>
> Yes, the output stops here. Don't know why ...

Ok.  I'm guessing that whatever it is immediately after
the e820 map dump causes the box to go south.

But this is a very good clue that your BIOS just can't
handle being run after the linux kernel has run at
this point.  Unfortunately this is common and why
the --real-mode switch has not been the default for several years.

What is your interest in getting the --real-mode option working at this
point?

After this point the debugging starts to get very laborious.

Eric