diff --git a/Documentation/ABI/testing/dev-kmsg b/Documentation/ABI/testing/dev-kmsg
index bb820be48179..fff817efa508 100644
--- a/Documentation/ABI/testing/dev-kmsg
+++ b/Documentation/ABI/testing/dev-kmsg
@@ -98,4 +98,13 @@ Description:	The /dev/kmsg character device node provides userspace access
 		logic is used internally when messages are printed to the
 		console, /proc/kmsg or the syslog() syscall.
 
+		By default, kernel tries to avoid fragments by concatenating
+		when it can and fragments are rare; however, when extended
+		console support is enabled, the in-kernel concatenation is
+		disabled and /dev/kmsg output will contain more fragments. If
+		the log consumer performs concatenation, the end result
+		should be the same. In the future, the in-kernel concatenation
+		may be removed entirely and /dev/kmsg users are recommended to
+		implement fragment handling.
+
 Users:		dmesg(1), userspace kernel log consumers
diff --git a/include/linux/console.h b/include/linux/console.h
index 9f50fb413c11..bd194343c346 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -115,6 +115,7 @@ static inline int con_debug_leave(void)
 #define CON_BOOT	(8)
 #define CON_ANYTIME	(16) /* Safe to call when cpu is offline */
 #define CON_BRL		(32) /* Used for a braille device */
+#define CON_EXTENDED	(64) /* Use the extended output format a la /dev/kmsg */
 
 struct console {
 	char	name[16];
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 51ce4f1838b3..ae980dc3ac1e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -84,6 +84,18 @@ static struct lockdep_map console_lock_dep_map = {
 };
 #endif
 
+/*
+ * Number of registered extended console drivers.
+ *
+ * If extended consoles are present, in-kernel cont reassembly is disabled
+ * and each fragment is stored as a separate log entry with proper
+ * continuation flag so that every emitted message has full metadata.  This
+ * doesn't change the result for regular consoles or /proc/kmsg.  For
+ * /dev/kmsg, as long as the reader concatenates messages according to
+ * consecutive continuation flags, the end result should be the same too.
+ */
+static int nr_ext_console_drivers;
+
 /*
  * Helper macros to handle lockdep when locking/unlocking console_sem. We use
  * macros instead of functions so that _RET_IP_ contains useful information.
@@ -195,7 +207,7 @@ static int console_may_schedule;
  * need to be changed in the future, when the requirements change.
  *
  * /dev/kmsg exports the structured data in the following line format:
- *   "level,sequnum,timestamp;<message text>\n"
+ *   "<level>,<sequnum>,<timestamp>,<contflag>;<message text>\n"
  *
  * The optional key/value pairs are attached as continuation lines starting
  * with a space character and terminated by a newline. All possible
@@ -1417,7 +1429,9 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
  * log_buf[start] to log_buf[end - 1].
  * The console_lock must be held.
  */
-static void call_console_drivers(int level, const char *text, size_t len)
+static void call_console_drivers(int level,
+				 const char *ext_text, size_t ext_len,
+				 const char *text, size_t len)
 {
 	struct console *con;
 
@@ -1438,7 +1452,10 @@ static void call_console_drivers(int level, const char *text, size_t len)
 		if (!cpu_online(smp_processor_id()) &&
 		    !(con->flags & CON_ANYTIME))
 			continue;
-		con->write(con, text, len);
+		if (con->flags & CON_EXTENDED)
+			con->write(con, ext_text, ext_len);
+		else
+			con->write(con, text, len);
 	}
 }
 
@@ -1581,8 +1598,12 @@ static bool cont_add(int facility, int level, const char *text, size_t len)
 	if (cont.len && cont.flushed)
 		return false;
 
-	if (cont.len + len > sizeof(cont.buf)) {
-		/* the line gets too long, split it up in separate records */
+	/*
+	 * If ext consoles are present, flush and skip in-kernel
+	 * continuation.  See nr_ext_console_drivers definition.  Also, if
+	 * the line gets too long, split it up in separate records.
+	 */
+	if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
 		cont_flush(LOG_CONT);
 		return false;
 	}
@@ -1917,9 +1938,19 @@ static struct cont {
 	u8 level;
 	bool flushed:1;
 } cont;
+static char *log_text(const struct printk_log *msg) { return NULL; }
+static char *log_dict(const struct printk_log *msg) { return NULL; }
 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
 static u32 log_next(u32 idx) { return 0; }
-static void call_console_drivers(int level, const char *text, size_t len) {}
+static ssize_t msg_print_ext_header(char *buf, size_t size,
+				    struct printk_log *msg, u64 seq,
+				    enum log_flags prev_flags) { return 0; }
+static ssize_t msg_print_ext_body(char *buf, size_t size,
+				  char *dict, size_t dict_len,
+				  char *text, size_t text_len) { return 0; }
+static void call_console_drivers(int level,
+				 const char *ext_text, size_t ext_len,
+				 const char *text, size_t len) {}
 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
 			     bool syslog, char *buf, size_t size) { return 0; }
 static size_t cont_print_text(char *text, size_t size) { return 0; }
@@ -2172,7 +2203,7 @@ static void console_cont_flush(char *text, size_t size)
 	len = cont_print_text(text, size);
 	raw_spin_unlock(&logbuf_lock);
 	stop_critical_timings();
-	call_console_drivers(cont.level, text, len);
+	call_console_drivers(cont.level, NULL, 0, text, len);
 	start_critical_timings();
 	local_irq_restore(flags);
 	return;
@@ -2196,6 +2227,7 @@ static void console_cont_flush(char *text, size_t size)
  */
 void console_unlock(void)
 {
+	static char ext_text[CONSOLE_EXT_LOG_MAX];
 	static char text[LOG_LINE_MAX + PREFIX_MAX];
 	static u64 seen_seq;
 	unsigned long flags;
@@ -2214,6 +2246,7 @@ void console_unlock(void)
 again:
 	for (;;) {
 		struct printk_log *msg;
+		size_t ext_len = 0;
 		size_t len;
 		int level;
 
@@ -2259,13 +2292,22 @@ void console_unlock(void)
 		level = msg->level;
 		len += msg_print_text(msg, console_prev, false,
 				      text + len, sizeof(text) - len);
+		if (nr_ext_console_drivers) {
+			ext_len = msg_print_ext_header(ext_text,
+						sizeof(ext_text),
+						msg, console_seq, console_prev);
+			ext_len += msg_print_ext_body(ext_text + ext_len,
+						sizeof(ext_text) - ext_len,
+						log_dict(msg), msg->dict_len,
+						log_text(msg), msg->text_len);
+		}
 		console_idx = log_next(console_idx);
 		console_seq++;
 		console_prev = msg->flags;
 		raw_spin_unlock(&logbuf_lock);
 
 		stop_critical_timings();	/* don't trace print latency */
-		call_console_drivers(level, text, len);
+		call_console_drivers(level, ext_text, ext_len, text, len);
 		start_critical_timings();
 		local_irq_restore(flags);
 	}
@@ -2521,6 +2563,11 @@ void register_console(struct console *newcon)
 		newcon->next = console_drivers->next;
 		console_drivers->next = newcon;
 	}
+
+	if (newcon->flags & CON_EXTENDED)
+		if (!nr_ext_console_drivers++)
+			pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*
 		 * console_unlock(); will print out the buffered messages
@@ -2593,6 +2640,9 @@ int unregister_console(struct console *console)
 		}
 	}
 
+	if (!res && (console->flags & CON_EXTENDED))
+		nr_ext_console_drivers--;
+
 	/*
 	 * If this isn't the last console and it has CON_CONSDEV set, we
 	 * need to set it on the next preferred console.