[PATCH] use ljmp to reboot (Re: at_keyboard flush on i386-qemu)

[Robert Millan]

On Sat, Jun 27, 2009 at 01:25:21PM +0200, Robert Millan wrote:
> 
> Hi,
> 
> Pavel pointed out earlier that sometimes when starting on i386-qemu GRUB
> receives spurious events from AT keyboard.  It seems that it is the role
> of the firmware to flush this buffer at startup.
> 
> Unless someone has a better idea, I would fix this with:
> 
>   - Moving at_keyboard to kernel on i386-qemu.
> 
>   - [ifdef GRUB_MACHINE_QEMU]: flush the input buffer at at_keyboard
>     startup by reading and discarding events for a fixed amount of time.
> 
> I don't like that we have a race here.  Suggestions welcome on how to
> improve that, but TTBOMK if there's more than one event you can't tell
> when you're processing the last one.

Actually I diagnosed this completely wrong.  The real problem is we're
using the keyboard to reboot the machine, which (at least on QEMU) results
in spurious keys being put in the buffer.

I think we should just jump to 0xffff0 to reboot.  I didn't know back when I
wrote reboot.c, but this is supposedly more reliable since we're jumping to
code in ROM which hasn't been overwritten (kern/i386/pc/startup.S uses the
same trick for its own grub_reboot()).

See attached patch.

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."

reboot.diff
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