[SeaBIOS] vgabios -> seabios breaks (my) 16-bit applications

[Paolo Bonzini]

On 12/01/2015 16:59, Richard Laager wrote:
> On Mon, 2015-01-12 at 10:32 -0500, Kevin O'Connor wrote:
>> Interesting.  Does your original business app then also work with
>> CONFIG_VGA_ALLOCATE_EXTRA_STACK disabled?
> 
> Yes. I couldn't be sure if I tested before, since I didn't write it
> down. But I just tested now.
> 
> Obviously this extra stack feature exists for a reason. What are the
> implications of turning it off?

commit 4a8b58cb6cccc8f6431167dfdd36f3e39601ff79
Author: Kevin O'Connor <kevin at koconnor.net>
Date:   Sat Nov 30 19:16:15 2013 -0500

    vgabios: Support allocating an extra stack for vgabios calls and default on.
    
    Add code to allocate an extra stack for the main vgabios int 0x10
    entry point.  The allocation is done via the PMM spec and uses a PCI
    v3 permanent low memory region request.  This request will work with
    SeaBIOS - it is unknown how many other main BIOS implementations
    support this PMM call.
    
    The extra stack is useful for old DOS programs that call the VGABIOS
    and expect it to work with very small amounts of stack space.
    
    Signed-off-by: Kevin O'Connor <kevin at koconnor.net>

Paolo