6 files changed, 28 insertions, 9 deletions
diff --git a/src/arch/i386/include/bios.h b/src/arch/i386/include/bios.h
index fadb9f1b7..3e6a845e3 100644
--- a/src/arch/i386/include/bios.h
+++ b/src/arch/i386/include/bios.h
@@ -6,6 +6,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define BDA_SEG 0x0040
 #define BDA_EQUIPMENT_WORD 0x0010
 #define BDA_FBMS 0x0013
+#define BDA_REBOOT 0x0072
+#define BDA_REBOOT_WARM 0x1234
 #define BDA_NUM_DRIVES 0x0075
 
 #endif /* BIOS_H */
diff --git a/src/arch/i386/interface/pcbios/bios_reboot.c b/src/arch/i386/interface/pcbios/bios_reboot.c
index 86f4e3eb3..68546b2e5 100644
--- a/src/arch/i386/interface/pcbios/bios_reboot.c
+++ b/src/arch/i386/interface/pcbios/bios_reboot.c
@@ -27,12 +27,19 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <ipxe/reboot.h>
 #include <realmode.h>
+#include <bios.h>
 
 /**
  * Reboot system
  *
+ * @v warm		Perform a warm reboot
  */
-static void bios_reboot ( void ) {
+static void bios_reboot ( int warm ) {
+	uint16_t flag;
+
+	/* Configure BIOS for cold/warm reboot */
+	flag = ( warm ? BDA_REBOOT_WARM : 0 );
+	put_real ( flag, BDA_SEG, BDA_REBOOT );
 
 	/* Jump to system reset vector */
 	__asm__ __volatile__ ( REAL_CODE ( "ljmp $0xf000, $0xfff0" ) : : );
diff --git a/src/core/null_reboot.c b/src/core/null_reboot.c
index b7e55bce8..8e3ed0bb6 100644
--- a/src/core/null_reboot.c
+++ b/src/core/null_reboot.c
@@ -32,8 +32,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
 /**
  * Reboot system
  *
+ * @v warm		Perform a warm reboot
  */
-static void null_reboot ( void ) {
+static void null_reboot ( int warm __unused ) {
 
 	printf ( "Cannot reboot; not implemented\n" );
 	while ( 1 ) {}
diff --git a/src/hci/commands/reboot_cmd.c b/src/hci/commands/reboot_cmd.c
index 19d3d6df4..44dcfc71c 100644
--- a/src/hci/commands/reboot_cmd.c
+++ b/src/hci/commands/reboot_cmd.c
@@ -17,6 +17,7 @@
  * 02110-1301, USA.
  */
 
+#include <getopt.h>
 #include <ipxe/command.h>
 #include <ipxe/parseopt.h>
 #include <ipxe/reboot.h>
@@ -30,14 +31,20 @@ FILE_LICENCE ( GPL2_OR_LATER );
  */
 
 /** "reboot" options */
-struct reboot_options {};
+struct reboot_options {
+	/** Perform a warm reboot */
+	int warm;
+};
 
 /** "reboot" option list */
-static struct option_descriptor reboot_opts[] = {};
+static struct option_descriptor reboot_opts[] = {
+	OPTION_DESC ( "warm", 'w', no_argument,
+		      struct reboot_options, warm, parse_flag ),
+};
 
 /** "reboot" command descriptor */
 static struct command_descriptor reboot_cmd =
-	COMMAND_DESC ( struct reboot_options, reboot_opts, 0, 0, "" );
+	COMMAND_DESC ( struct reboot_options, reboot_opts, 0, 0, "[--warm]" );
 
 /**
  * The "reboot" command
@@ -55,7 +62,7 @@ static int reboot_exec ( int argc, char **argv ) {
 		return rc;
 
 	/* Reboot system */
-	reboot();
+	reboot ( opts.warm );
 
 	return 0;
 }
diff --git a/src/include/ipxe/reboot.h b/src/include/ipxe/reboot.h
index 043c5e10b..5d882d3dd 100644
--- a/src/include/ipxe/reboot.h
+++ b/src/include/ipxe/reboot.h
@@ -51,7 +51,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
 /**
  * Reboot system
  *
+ * @v warm		Perform a warm reboot
  */
-void reboot ( void );
+void reboot ( int warm );
 
 #endif /* _IPXE_REBOOT_H */
diff --git a/src/interface/efi/efi_reboot.c b/src/interface/efi/efi_reboot.c
index 1ecccc460..bfee36aa3 100644
--- a/src/interface/efi/efi_reboot.c
+++ b/src/interface/efi/efi_reboot.c
@@ -32,12 +32,13 @@ FILE_LICENCE ( GPL2_OR_LATER );
 /**
  * Reboot system
  *
+ * @v warm		Perform a warm reboot
  */
-static void efi_reboot ( void ) {
+static void efi_reboot ( int warm ) {
 	EFI_RUNTIME_SERVICES *rs = efi_systab->RuntimeServices;
 
 	/* Use runtime services to reset system */
-	rs->ResetSystem ( EfiResetCold, 0, 0, NULL );
+	rs->ResetSystem ( ( warm ? EfiResetWarm : EfiResetCold ), 0, 0, NULL );
 }
 
 PROVIDE_REBOOT ( efi, reboot, efi_reboot );