[PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic

[Eric W. Biederman]

Ingo Molnar <mingo at elte.hu> writes:

> * H. Peter Anvin <hpa at zytor.com> wrote:
>
>> On 01/26/2011 06:00 AM, Ingo Molnar wrote:
>> >
>> >I mean, use the warm reset vector to truly reset the box.
>> >
>> >Then, once a stable known-good kernel boots, *that* kernel can then recover all the
>> >log data which is sitting in a well-known place in RAM, automatically and
>> >transparently.
>> >
>> >Basically a bit like kexec, just more convenient and it also goes through the BIOS
>> >warm reset, so it might work better than kexec ...
>> >
>> 
>> The problem is that the BIOS will often wipe memory.
>
> Yes - but at least a long time ago there used to be modi of reboot when the BIOS did 
> not do this. Whether that's possible at all with modern BIOSen is a
> big question ...

As I recall that was how you went from 32bit mode to 16bit real mode.
The issue is that mode never reset the hardware it simply changed the
cpu mode.

Eric