- Needed for SGABIOS option ROM for VMM. Normally these are setup based on
  the QEMU fw_cfg interface (or coreboot CBFS on hardware).

Index: src/optionroms.c
--- src/optionroms.c.orig
+++ src/optionroms.c
@@ -387,7 +387,7 @@ optionrom_setup(void)
 
     // All option roms found and deployed - now build BEV/BCV vectors.
 
-    u32 pos = post_vga;
+    u32 pos = BUILD_BIOS_ADDR - BUILD_ROM_START;
     while (pos < rom_get_last()) {
         struct rom_header *rom = (void*)pos;
         if (! is_valid_rom(rom)) {