Also hide base memory region from E820 map.

src/arch/i386/firmware/pcbios/hidemem.c

  */
 enum {
 	TEXT = 0,
+	BASEMEM,
 };
 
 /**
  */
 struct hidden_region __data16_array ( hidden_regions, [] ) = {
 	[TEXT] = { 0, 0 },
+	[BASEMEM] = { 0, ( 640 * 1024 ) },
 	{ 0, 0, } /* Terminator */
 };
 #define hidden_regions __use_data16 ( hidden_regions )
 void hide_etherboot ( void ) {
 	hidden_regions[TEXT].start = virt_to_phys ( _text );
 	hidden_regions[TEXT].end = virt_to_phys ( _end );
+	hidden_regions[BASEMEM].start = ( rm_cs << 4 );
 
-	DBG ( "Hiding [%lx,%lx)\n",
+	DBG ( "Hiding [%lx,%lx) and [%lx,%lx)\n",
 	      ( unsigned long ) hidden_regions[TEXT].start,
-	      ( unsigned long ) hidden_regions[TEXT].end );
+	      ( unsigned long ) hidden_regions[TEXT].end,
+	      ( unsigned long ) hidden_regions[BASEMEM].start,
+	      ( unsigned long ) hidden_regions[BASEMEM].end );
 
 	hook_bios_interrupt ( 0x15, ( unsigned int ) int15,
 			      &int15_vector );