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diff --git a/include/uapi/linux/um_timetravel.h b/include/uapi/linux/um_timetravel.h
new file mode 100644
index 000000000000..546a690b0346
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+++ b/include/uapi/linux/um_timetravel.h
@@ -0,0 +1,290 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Copyright (C) 2019 - 2023 Intel Corporation
+ */
+#ifndef _UAPI_LINUX_UM_TIMETRAVEL_H
+#define _UAPI_LINUX_UM_TIMETRAVEL_H
+#include <linux/types.h>
+
+/**
+ * struct um_timetravel_msg - UM time travel message
+ *
+ * This is the basic message type, going in both directions.
+ *
+ * This is the message passed between the host (user-mode Linux instance)
+ * and the calendar (the application on the other side of the socket) in
+ * order to implement common scheduling.
+ *
+ * Whenever UML has an event it will request runtime for it from the
+ * calendar, and then wait for its turn until it can run, etc. Note
+ * that it will only ever request the single next runtime, i.e. multiple
+ * REQUEST messages override each other.
+ */
+struct um_timetravel_msg {
+	/**
+	 * @op: operation value from &enum um_timetravel_ops
+	 */
+	__u32 op;
+
+	/**
+	 * @seq: sequence number for the message - shall be reflected in
+	 *	the ACK response, and should be checked while processing
+	 *	the response to see if it matches
+	 */
+	__u32 seq;
+
+	/**
+	 * @time: time in nanoseconds
+	 */
+	__u64 time;
+};
+
+/* max number of file descriptors that can be sent/received in a message */
+#define UM_TIMETRAVEL_MAX_FDS 2
+
+/**
+ * enum um_timetravel_shared_mem_fds - fds sent in ACK message for START message
+ */
+enum um_timetravel_shared_mem_fds {
+	/**
+	 * @UM_TIMETRAVEL_SHARED_MEMFD: Index of the shared memory file
+	 *	descriptor in the control message
+	 */
+	UM_TIMETRAVEL_SHARED_MEMFD,
+	/**
+	 * @UM_TIMETRAVEL_SHARED_LOGFD: Index of the logging file descriptor
+	 *	in the control message
+	 */
+	UM_TIMETRAVEL_SHARED_LOGFD,
+	UM_TIMETRAVEL_SHARED_MAX_FDS,
+};
+
+/**
+ * enum um_timetravel_start_ack - ack-time mask for start message
+ */
+enum um_timetravel_start_ack {
+	/**
+	 * @UM_TIMETRAVEL_START_ACK_ID: client ID that controller allocated.
+	 */
+	UM_TIMETRAVEL_START_ACK_ID = 0xffff,
+};
+
+/**
+ * enum um_timetravel_ops - Operation codes
+ */
+enum um_timetravel_ops {
+	/**
+	 * @UM_TIMETRAVEL_ACK: response (ACK) to any previous message,
+	 *	this usually doesn't carry any data in the 'time' field
+	 *	unless otherwise specified below, note: while using shared
+	 *	memory no ACK for WAIT and RUN messages, for more info see
+	 *	&struct um_timetravel_schedshm.
+	 */
+	UM_TIMETRAVEL_ACK		= 0,
+
+	/**
+	 * @UM_TIMETRAVEL_START: initialize the connection, the time
+	 *	field contains an (arbitrary) ID to possibly be able
+	 *	to distinguish the connections.
+	 */
+	UM_TIMETRAVEL_START		= 1,
+
+	/**
+	 * @UM_TIMETRAVEL_REQUEST: request to run at the given time
+	 *	(host -> calendar)
+	 */
+	UM_TIMETRAVEL_REQUEST		= 2,
+
+	/**
+	 * @UM_TIMETRAVEL_WAIT: Indicate waiting for the previously requested
+	 *	runtime, new requests may be made while waiting (e.g. due to
+	 *	interrupts); the time field is ignored. The calendar must process
+	 *	this message and later	send a %UM_TIMETRAVEL_RUN message when
+	 *	the host can run again.
+	 *	(host -> calendar)
+	 */
+	UM_TIMETRAVEL_WAIT		= 3,
+
+	/**
+	 * @UM_TIMETRAVEL_GET: return the current time from the calendar in the
+	 *	ACK message, the time in the request message is ignored
+	 *	(host -> calendar)
+	 */
+	UM_TIMETRAVEL_GET		= 4,
+
+	/**
+	 * @UM_TIMETRAVEL_UPDATE: time update to the calendar, must be sent e.g.
+	 *	before kicking an interrupt to another calendar
+	 *	(host -> calendar)
+	 */
+	UM_TIMETRAVEL_UPDATE		= 5,
+
+	/**
+	 * @UM_TIMETRAVEL_RUN: run time request granted, current time is in
+	 *	the time field
+	 *	(calendar -> host)
+	 */
+	UM_TIMETRAVEL_RUN		= 6,
+
+	/**
+	 * @UM_TIMETRAVEL_FREE_UNTIL: Enable free-running until the given time,
+	 *	this is a message from the calendar telling the host that it can
+	 *	freely do its own scheduling for anything before the indicated
+	 *	time.
+	 *	Note that if a calendar sends this message once, the host may
+	 *	assume that it will also do so in the future, if it implements
+	 *	wraparound semantics for the time field.
+	 *	(calendar -> host)
+	 */
+	UM_TIMETRAVEL_FREE_UNTIL	= 7,
+
+	/**
+	 * @UM_TIMETRAVEL_GET_TOD: Return time of day, typically used once at
+	 *	boot by the virtual machines to get a synchronized time from
+	 *	the simulation.
+	 */
+	UM_TIMETRAVEL_GET_TOD		= 8,
+
+	/**
+	 * @UM_TIMETRAVEL_BROADCAST: Send/Receive a broadcast message.
+	 *	This message can be used to sync all components in the system
+	 *	with a single message, if the calender gets the message, the
+	 *	calender broadcast the message to all components, and if a
+	 *	component receives it it should act based on it e.g print a
+	 *	message to it's log system.
+	 *	(calendar <-> host)
+	 */
+	UM_TIMETRAVEL_BROADCAST		= 9,
+};
+
+/* version of struct um_timetravel_schedshm */
+#define UM_TIMETRAVEL_SCHEDSHM_VERSION 2
+
+/**
+ * enum um_timetravel_schedshm_cap - time travel capabilities of every client
+ *
+ * These flags must be set immediately after processing the ACK to
+ * the START message, before sending any message to the controller.
+ */
+enum um_timetravel_schedshm_cap {
+	/**
+	 * @UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE: client can read current time
+	 *	update internal time request to shared memory and read
+	 *	free until and send no Ack on RUN and doesn't expect ACK on
+	 *	WAIT.
+	 */
+	UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE = 0x1,
+};
+
+/**
+ * enum um_timetravel_schedshm_flags - time travel flags of every client
+ */
+enum um_timetravel_schedshm_flags {
+	/**
+	 * @UM_TIMETRAVEL_SCHEDSHM_FLAGS_REQ_RUN: client has a request to run.
+	 *	It's set by client when it has a request to run, if (and only
+	 *	if) the @running_id points to a client that is able to use
+	 *	shared memory, i.e. has %UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE
+	 *	(this includes the client itself). Otherwise, a message must
+	 *	be used.
+	 */
+	UM_TIMETRAVEL_SCHEDSHM_FLAGS_REQ_RUN = 0x1,
+};
+
+/**
+ * DOC: Time travel shared memory overview
+ *
+ * The main purpose of the shared memory is to avoid all time travel message
+ * that don't need any action, for example current time can be held in shared
+ * memory without the need of any client to send a message UM_TIMETRAVEL_GET
+ * in order to know what's the time.
+ *
+ * Since this is shared memory with all clients and controller and controller
+ * creates the shared memory space, all time values are absolute to controller
+ * time. So first time client connects to shared memory mode it should take the
+ * current_time value in shared memory and keep it internally as a diff to
+ * shared memory times, and once shared memory is initialized, any interaction
+ * with the controller must happen in the controller time domain, including any
+ * messages (for clients that are not using shared memory, the controller will
+ * handle an offset and make the clients think they start at time zero.)
+ *
+ * Along with the shared memory file descriptor is sent to the client a logging
+ * file descriptor, to have all logs related to shared memory,
+ * logged into one place. note: to have all logs synced into log file at write,
+ * file should be flushed (fflush) after writing to it.
+ *
+ * To avoid memory corruption, we define below for each field who can write to
+ * it at what time, defined in the structure fields.
+ *
+ * To avoid having to pack this struct, all fields in it must be naturally aligned
+ * (i.e. aligned to their size).
+ */
+
+/**
+ * union um_timetravel_schedshm_client - UM time travel client struct
+ *
+ * Every entity using the shared memory including the controller has a place in
+ * the um_timetravel_schedshm clients array, that holds info related to the client
+ * using the shared memory, and can be set only by the client after it gets the
+ * fd memory.
+ *
+ * @capa: bit fields with client capabilities see
+ *	&enum um_timetravel_schedshm_cap, set by client once after getting the
+ *	shared memory file descriptor.
+ * @flags: bit fields for flags see &enum um_timetravel_schedshm_flags for doc.
+ * @req_time: request time to run, set by client on every request it needs.
+ * @name: unique id sent to the controller by client with START message.
+ */
+union um_timetravel_schedshm_client {
+	struct {
+		__u32 capa;
+		__u32 flags;
+		__u64 req_time;
+		__u64 name;
+	};
+	char reserve[128]; /* reserved for future usage */
+};
+
+/**
+ * struct um_timetravel_schedshm - UM time travel shared memory struct
+ *
+ * @hdr: header fields:
+ * @version: Current version struct UM_TIMETRAVEL_SCHEDSHM_VERSION,
+ *	set by controller once at init, clients must check this after mapping
+ *	and work without shared memory if they cannot handle the indicated
+ *	version.
+ * @len: Length of all the memory including header (@hdr), clients should once
+ *	per connection first mmap the header and take the length (@len) to remap the entire size.
+ *	This is done in order to support dynamic struct size letting number of
+ *	clients be dynamic based on controller support.
+ * @free_until: Stores the next request to run by any client, in order for the
+ *	current client to know how long it can still run. A client needs to (at
+ *	least) reload this value immediately after communicating with any other
+ *	client, since the controller will update this field when a new request
+ *	is made by any client. Clients also must update this value when they
+ *	insert/update an own request into the shared memory while not running
+ *	themselves, and the new request is before than the current value.
+ * current_time: Current time, can only be set by the client in running state
+ *	(indicated by @running_id), though that client may only run until @free_until,
+ *	so it must remain smaller than @free_until.
+ * @running_id: The current client in state running, set before a client is
+ *	notified that it's now running.
+ * @max_clients: size of @clients array, set once at init by the controller.
+ * @clients: clients array see &union um_timetravel_schedshm_client for doc,
+ *	set only by client.
+ */
+struct um_timetravel_schedshm {
+	union {
+		struct {
+			__u32 version;
+			__u32 len;
+			__u64 free_until;
+			__u64 current_time;
+			__u16 running_id;
+			__u16 max_clients;
+		};
+		char hdr[4096]; /* align to 4K page size */
+	};
+	union um_timetravel_schedshm_client clients[];
+};
+#endif /* _UAPI_LINUX_UM_TIMETRAVEL_H */