EBX: Contains the VM handle (always the currently executing VM).
ECX: Contains the VESA BIOS mode number that is currently running.
EBP: Points to the Windows VM's Client Registers.
Save everything that you use. CY returned means that mini-VDD handled the call. EDX contains the current bank size. EAX contains the physical address of the memory aperture or zero to indicate a standard memory aperture at physical address A000:0h.
This routine is called during the save process of a VESA hi-res screen. It tells the Main VDD how large each bank is (so that during the save and restore process, it will know how many bytes to process per pass of the save/restore loop). It also informs the Main VDD where to access the VRAM. Most VESA programs currently set their VRAM at A000:0h. However, VESA version 2 does allow for flat linear apertures. The mini-VDD should determine if the VESA program is using an aperture and return the correct data to the Main VDD.