diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index bccd341e9ae1..5c4e4a8771cf 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -1077,7 +1077,7 @@ static int configure_kgdbts(void)
 	final_ack = 0;
 	run_plant_and_detach_test(1);
 
-	err = kgdb_register_io_module(&kgdbts_io_ops);
+	err = kgdb_register_io_module(&kgdbts_io_ops, false);
 	if (err) {
 		configured = 0;
 		return err;
diff --git a/drivers/tty/mips_ejtag_fdc.c b/drivers/tty/mips_ejtag_fdc.c
index 21e76a2ec182..68817cca39ce 100644
--- a/drivers/tty/mips_ejtag_fdc.c
+++ b/drivers/tty/mips_ejtag_fdc.c
@@ -1265,7 +1265,7 @@ static struct kgdb_io kgdbfdc_io_ops = {
 
 static int __init kgdbfdc_init(void)
 {
-	kgdb_register_io_module(&kgdbfdc_io_ops);
+	kgdb_register_io_module(&kgdbfdc_io_ops, false);
 	return 0;
 }
 early_initcall(kgdbfdc_init);
diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 519d8cfbfbed..2f526f2d2bea 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -21,6 +21,7 @@
 #include <linux/input.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/serial_core.h>
 
 #define MAX_CONFIG_LEN		40
 
@@ -42,6 +43,14 @@ static int			kgdb_tty_line;
 
 static struct platform_device *kgdboc_pdev;
 
+#ifdef CONFIG_KGDB_SERIAL_CONSOLE
+static struct kgdb_io		earlycon_kgdboc_io_ops;
+struct console			*earlycon;
+bool				earlycon_neutered;
+#else /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+#define earlycon NULL
+#endif /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+
 #ifdef CONFIG_KDB_KEYBOARD
 static int kgdboc_reset_connect(struct input_handler *handler,
 				struct input_dev *dev,
@@ -135,8 +144,46 @@ static void kgdboc_unregister_kbd(void)
 #define kgdboc_restore_input()
 #endif /* ! CONFIG_KDB_KEYBOARD */
 
+#ifdef CONFIG_KGDB_SERIAL_CONSOLE
+
+static void cleanup_earlycon(bool unregister)
+{
+	if (earlycon && unregister)
+		kgdb_unregister_io_module(&earlycon_kgdboc_io_ops);
+	earlycon = NULL;
+}
+
+static bool is_earlycon_still_valid(void)
+{
+	struct console *con;
+
+	for_each_console(con)
+		if (con == earlycon)
+			return true;
+	return false;
+}
+
+static void cleanup_earlycon_if_invalid(void)
+{
+	console_lock();
+	if (earlycon && (earlycon_neutered || !is_earlycon_still_valid())) {
+		pr_warn("earlycon vanished; unregistering\n");
+		cleanup_earlycon(true);
+	}
+	console_unlock();
+}
+
+#else /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+
+static inline void cleanup_earlycon(bool unregister) { ; }
+static inline void cleanup_earlycon_if_invalid(void) { ; }
+
+#endif /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+
 static void cleanup_kgdboc(void)
 {
+	cleanup_earlycon(true);
+
 	if (configured != 1)
 		return;
 
@@ -188,9 +235,10 @@ static int configure_kgdboc(void)
 	kgdb_tty_line = tty_line;
 
 do_register:
-	err = kgdb_register_io_module(&kgdboc_io_ops);
+	err = kgdb_register_io_module(&kgdboc_io_ops, earlycon != NULL);
 	if (err)
 		goto noconfig;
+	cleanup_earlycon(false);
 
 	err = kgdb_register_nmi_console();
 	if (err)
@@ -206,6 +254,14 @@ static int configure_kgdboc(void)
 	kgdboc_unregister_kbd();
 	configured = 0;
 
+	/*
+	 * Each time we run configure_kgdboc() but don't find a console, use
+	 * that as a chance to validate that our earlycon didn't vanish on
+	 * us.  If it vanished we should unregister which will disable kgdb
+	 * if we're the last I/O module.
+	 */
+	cleanup_earlycon_if_invalid();
+
 	return err;
 }
 
@@ -409,6 +465,80 @@ static int __init kgdboc_early_init(char *opt)
 }
 
 early_param("ekgdboc", kgdboc_early_init);
+
+static int earlycon_kgdboc_get_char(void)
+{
+	char c;
+
+	if (earlycon_neutered || !earlycon->read(earlycon, &c, 1))
+		return NO_POLL_CHAR;
+
+	return c;
+}
+
+static void earlycon_kgdboc_put_char(u8 chr)
+{
+	if (!earlycon_neutered)
+		earlycon->write(earlycon, &chr, 1);
+}
+
+static void earlycon_kgdboc_pre_exp_handler(void)
+{
+	/*
+	 * We don't get notified when the boot console is unregistered.
+	 * Double-check when we enter the debugger.  Unfortunately we
+	 * can't really unregister ourselves now, but at least don't crash.
+	 */
+	if (earlycon && !earlycon_neutered && !is_earlycon_still_valid()) {
+		pr_warn("Neutering kgdb since boot console vanished\n");
+		earlycon_neutered = true;
+	}
+}
+
+static struct kgdb_io earlycon_kgdboc_io_ops = {
+	.name			= "earlycon_kgdboc",
+	.read_char		= earlycon_kgdboc_get_char,
+	.write_char		= earlycon_kgdboc_put_char,
+	.pre_exception		= earlycon_kgdboc_pre_exp_handler,
+	.is_console		= true,
+};
+
+static int __init earlycon_kgdboc_init(char *opt)
+{
+	struct console *con;
+
+	kdb_init(KDB_INIT_EARLY);
+
+	/*
+	 * Look for a matching console, or if the name was left blank just
+	 * pick the first one we find.
+	 */
+	console_lock();
+	for_each_console(con) {
+		if (con->write && con->read &&
+		    (con->flags & (CON_BOOT | CON_ENABLED)) &&
+		    (!opt || !opt[0] || strcmp(con->name, opt) == 0))
+			break;
+	}
+	console_unlock();
+
+	if (!con) {
+		pr_info("Couldn't find kgdb earlycon\n");
+		return 0;
+	}
+
+	earlycon = con;
+	pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
+	if (kgdb_register_io_module(&earlycon_kgdboc_io_ops, false) != 0) {
+		earlycon = NULL;
+		pr_info("Failed to register kgdb with earlycon\n");
+		return 0;
+	}
+
+	return 0;
+}
+
+early_param("earlycon_kgdboc", earlycon_kgdboc_init);
 #endif /* CONFIG_KGDB_SERIAL_CONSOLE */
 
 module_init(init_kgdboc);
diff --git a/drivers/usb/early/ehci-dbgp.c b/drivers/usb/early/ehci-dbgp.c
index ea0d531c63e2..bb04c688e094 100644
--- a/drivers/usb/early/ehci-dbgp.c
+++ b/drivers/usb/early/ehci-dbgp.c
@@ -1057,7 +1057,7 @@ static int __init kgdbdbgp_parse_config(char *str)
 		ptr++;
 		kgdbdbgp_wait_time = simple_strtoul(ptr, &ptr, 10);
 	}
-	kgdb_register_io_module(&kgdbdbgp_io_ops);
+	kgdb_register_io_module(&kgdbdbgp_io_ops, false);
 	kgdbdbgp_io_ops.is_console = early_dbgp_console.index != -1;
 
 	return 0;
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 7371517aeacc..2e86307f2683 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -323,7 +323,8 @@ static inline int kgdb_unregister_nmi_console(void) { return 0; }
 static inline bool kgdb_nmi_poll_knock(void) { return 1; }
 #endif
 
-extern int kgdb_register_io_module(struct kgdb_io *local_kgdb_io_ops);
+extern int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops,
+				   bool replace);
 extern void kgdb_unregister_io_module(struct kgdb_io *local_kgdb_io_ops);
 extern struct kgdb_io *dbg_io_ops;
 
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 8f178239856d..1b5435c6d92a 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -1074,16 +1074,21 @@ EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 /**
  *	kgdb_register_io_module - register KGDB IO module
  *	@new_dbg_io_ops: the io ops vector
+ *	@replace: If true it's OK if there were old ops.  This is used
+ *		  to transition from early kgdb to normal kgdb.  It's
+ *		  assumed these are the same device so kgdb can continue.
  *
  *	Register it with the KGDB core.
  */
-int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
+int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops, bool replace)
 {
+	struct kgdb_io *old_dbg_io_ops;
 	int err;
 
 	spin_lock(&kgdb_registration_lock);
 
-	if (dbg_io_ops) {
+	old_dbg_io_ops = dbg_io_ops;
+	if (dbg_io_ops && !replace) {
 		spin_unlock(&kgdb_registration_lock);
 
 		pr_err("Another I/O driver is already registered with KGDB\n");
@@ -1102,6 +1107,12 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 
 	spin_unlock(&kgdb_registration_lock);
 
+	if (replace) {
+		pr_info("Replaced I/O driver %s with %s\n",
+			old_dbg_io_ops->name, new_dbg_io_ops->name);
+		return 0;
+	}
+
 	pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
 
 	/* Arm KGDB now. */
