[ipxe-devel] console-command works in quem only with DEBUG enabled

Michael Brown mbrown at fensystems.co.uk
Fri Dec 6 03:11:44 UTC 2013

On 05/12/13 19:09, Oliver Rath wrote:
> Interesting detail: if I start qemu without "--vga std" it works fine.

Thanks; that allowed me to reproduce the problem!

It turned out to be a rather interesting bug in the qemu VGA BIOS:


The bug causes the %ebx and %edx registers to become corrupted.  If the 
iPXE code surrounding the call to INT 10,4f00 relies on values that were 
left in either of these registers, then weird things will happen.  (In 
my test setup, iPXE would try to use a mode list full of random garbage; 
this would sometimes work because one of the random numbers would happen 
to be a valid VESA mode!).

The latest code should work around this BIOS bug.

> FYI: Im testing console-background-picture in conjunction with menu, but
> at the moment with starting the menu, the pic is hided and comes back
> after finishing menu. Do you planning a feature for this? For the first,
> it would be enough for me, that the pic resides in menu-mode.

The plan is to allow for the menu colour scheme to be customised.  In 
particular, selecting the background colour as "transparent" rather than 
"blue" will allow the picture to show through.  You can get a rough idea 
of how this will look by hacking config/colour.h: change all instances 
of "COLOR_BLUE" to "9".


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