kexec --real-mode

[Eric W. Biederman]

Bernhard Walle <bwalle at suse.de> writes:

> Hi,
>
> * Eric W. Biederman [2008-04-23 07:00]:
>> Bernhard Walle <bwalle at suse.de> writes:
>> > * Jamey Sharp [2008-04-22 16:44]:
>> >>
>> >> On Tue, Apr 22, 2008 at 6:16 AM, Bernhard Walle <bwalle at suse.de> wrote:
>> >> > did anybody try the --real-mode option with current release? I tried
>> >> > it on two machines, and on one machine it just reboots, on the other
>> >> > machine it hangs.
>> >> 
>> >> I think you're experiencing a bug that I just proposed a patch for. :-)
>> >> You can confirm that: try adding the "--debug" option to your kexec
>> >> call. If that works correctly, then I think you'll find that the patch
>> >> in "[PATCH 2/9] Fix copy-paste bug: entry16 does not start at
>> >> entry16_debug" will solve your problem. That's archived here:
>> >> 
>> >> http://lists.infradead.org/pipermail/kexec/2008-April/001581.html
>> >
>> > No, I used --debug already.
>> 
>> If this used to work when booting older kernels on your hardware.
>> Jamey's patch 3/9 might help.
>
> Well, now it goes until DEBUG_CHAR('j'). But the kernel doesn't boot.
>
>> Otherwise if this is the first time you are trying it you may
>> simply have encountered the reason that --real-mode is not the default.
>> BIOS can get really strange after the kernel has been running.

> That might be the case. Thanks for the information.
>
>> You might try booting kexec_test and see where that puts you.
>
> But that's ELF and not bzImage.

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.

Eric