EBX: Contains the VM handle to modify state for.
Save anything that you use.
Certain pieces of display hardware are "modal" and must have some of their extended registers set to certain values depending on whether the application is accessing memory at one of the VGA apertures (such as A000h:xxxx) or if it is accessing memory using a flat linear frame buffer. This routine is called by the Main VDD to explicitly tell the mini-VDD to setup for accessing the flat linear frame buffer. See the sample S3 mini-VDD for an example of how this function is used.