[SeaBIOS] [PATCHv3] vgabios: Don't use extra stack if it appears a modern OS is in use

[Kevin O'Connor]

On Tue, Mar 17, 2015 at 11:54:31AM -0400, Kevin O'Connor wrote:
> If the last mode set (while not in vm86 mode) was done from a VBE mode
> set call then disable the extra stack.  This works under the premise
> that only a modern OS would invoke the VBE mode changing facilities
> and a modern OS would always call the vgabios with sufficient stack
> space.
> 
> This is an ugly hack to work around a problem Windows Vista (and
> possibly later Windows releases) has with the VGA BIOS using a stack
> in the e-segment.

FYI, I pushed (a slightly modified version of) this patch to the
master repo.

-Kevin