Re: [Qemu-devel] [PATCH] x86: Manage BIOS boot menu via command line

[Paul Brook <paul@codesourcery.com>]

On Thursday 18 December 2008, Jan Kiszka wrote:
> When booting a guest from the command line, you normally do not need the
> interactive boot menu with its 3 s waiting that someone might press F12.
> So this patch introduces a mechanism to enable the boot menu only on
> demand, ie. when the user provided the command line switch -bootmenu.
> This reduces boot times to their original dimension.
>
> The host-guest interface used here is CMOS RAM byte 0x60. If it is
> non-zero, the guest BIOS will skip the F12 delay, keeping the previous
> behavior in case the host does not support it. -bootmenu was chosen in
> favor of -boot as the syntax of the latter is not easily and cleanly
> extensible.

I'm not sure I believe this. We already support multiple options to -boot so 
why not just add another one (e.g. "q") that means include the boot menu?
i.e. -boot qcad would give the current behaviour.

I've no particular preference whether this is communicated to the bios via the 
current 0x3d region or via a new byte. It looks like there's a spare bit in 
byte 0x38 that could be used.

Paul