diff --git a/hypervisor/arch/x86/Kconfig b/hypervisor/arch/x86/Kconfig
index 3244967ee..0e4819c1b 100644
--- a/hypervisor/arch/x86/Kconfig
+++ b/hypervisor/arch/x86/Kconfig
@@ -154,13 +154,15 @@ config CPU_UP_TIMEOUT
 	  for secondary CPUs to start up.
 
 choice
-	prompt "serial IO type"
+	prompt "Serial IO type"
 	depends on !RELEASE
-	default SERIAL_MMIO if PLATFORM_SBL
-	default SERIAL_PIO  if PLATFORM_UEFI
+	optional
 	help
-	  Whether the physical serial port shall be accessed via memory-mapped
-	  registers or I/O ports.
+	  If selected, this configures whether the physical serial port shall
+	  be accessed via memory-mapped registers or I/O ports.
+
+	  If this is not selected, the serial port is disabled. This is the
+	  default.
 
 config SERIAL_MMIO
 	bool "MMIO"
diff --git a/hypervisor/arch/x86/configs/apl-mrb.config b/hypervisor/arch/x86/configs/apl-mrb.config
index 5e87dc17f..71b03b332 100644
--- a/hypervisor/arch/x86/configs/apl-mrb.config
+++ b/hypervisor/arch/x86/configs/apl-mrb.config
@@ -1,5 +1,5 @@
+# Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
 CONFIG_BOARD="apl-mrb"
-# CONFIG_PLATFORM_UEFI is not set
-CONFIG_PLATFORM_SBL=y
+CONFIG_SERIAL_MMIO=y
 CONFIG_COM_BASE=0x3e8
 CONFIG_COM_IRQ=6
diff --git a/hypervisor/arch/x86/configs/cb2_dnv.config b/hypervisor/arch/x86/configs/cb2_dnv.config
index 17cd06f03..94c562bd8 100644
--- a/hypervisor/arch/x86/configs/cb2_dnv.config
+++ b/hypervisor/arch/x86/configs/cb2_dnv.config
@@ -1,7 +1,6 @@
-CONFIG_BOARD="cb2_dnv"
-CONFIG_PLATFORM_SBL=y
+# Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
 CONFIG_PARTITION_MODE=y
+CONFIG_BOARD="cb2_dnv"
 CONFIG_SERIAL_PIO=y
 CONFIG_SERIAL_PIO_BASE=0x1000
 CONFIG_DMAR_PARSE_ENABLED=y
-
diff --git a/hypervisor/arch/x86/configs/nuc6cayh.config b/hypervisor/arch/x86/configs/nuc6cayh.config
index 7ffdde65e..f056ac725 100644
--- a/hypervisor/arch/x86/configs/nuc6cayh.config
+++ b/hypervisor/arch/x86/configs/nuc6cayh.config
@@ -1,3 +1,4 @@
-CONFIG_BOARD="NUC6CAYH"
+# Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
 CONFIG_PLATFORM_UEFI=y
-# CONFIG_PLATFORM_SBL is not set
+CONFIG_BOARD="NUC6CAYH"
+CONFIG_SERIAL_PIO=y
diff --git a/hypervisor/arch/x86/configs/up2.config b/hypervisor/arch/x86/configs/up2.config
index a3f620724..45491fa00 100644
--- a/hypervisor/arch/x86/configs/up2.config
+++ b/hypervisor/arch/x86/configs/up2.config
@@ -1,3 +1,5 @@
-CONFIG_BOARD="UP2"
+# Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
 CONFIG_PLATFORM_UEFI=y
-# CONFIG_PLATFORM_SBL is not set
+CONFIG_BOARD="UP2"
+CONFIG_SERIAL_MMIO=y
+CONFIG_SERIAL_MMIO_BASE=0x9141e000
diff --git a/hypervisor/debug/uart16550.c b/hypervisor/debug/uart16550.c
index b787166fa..038d10c4d 100644
--- a/hypervisor/debug/uart16550.c
+++ b/hypervisor/debug/uart16550.c
@@ -16,7 +16,6 @@ static bool serial_port_mapped;
 static bool uart_enabled = true;
 #define UART_BASE_ADDRESS		CONFIG_SERIAL_MMIO_BASE
 #else
-#warning  "no uart base configure, please check!"
 static bool serial_port_mapped;
 static bool uart_enabled;
 #define UART_BASE_ADDRESS		0UL