Re: [PATCH] Use correct x86 reboot vector

[ebiederm@xmission.com (Eric W. Biederman)]

Davide Libenzi <davidel@xmailserver.org> writes:

> On Sun, 11 May 2003, Eric W. Biederman wrote:
> 
> > The remapping is quite common but it usually happens that after bootup:
> > 0xf0000-0xfffff is shadowed RAM.  While 0xffff0000-0xffffffff still points
> > to the rom chip.
> >
> > Now if someone could tell me how to do a jump to 0xffff0000:0xfff0 in real
> > mode I would find that very interesting.
> 
> Have you ever heard about unreal mode ? But I do not think that a reset
> has to start over there. I do not think that exist hw/sw that expect that
> reset address to be 0xfffffff0 instead of 0x000ffff0, since they map the
> same content.

There is some software at least that knows the difference.  I have seen short
jumps in a couple of BIOS's.  But a reset is very different from a
reboot.  As memory must be reinitialized etc.  So I think going to
0xffff0000:0xfff0 would be a very bad idea if the intent is to get a
reliable reboot.


Eric