diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index a722a1a8a48a..264daffedb09 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1573,7 +1573,7 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 			    enum vfio_device_mig_state cur_fsm,
 			    enum vfio_device_mig_state new_fsm)
 {
-	enum { VFIO_DEVICE_NUM_STATES = VFIO_DEVICE_STATE_RUNNING_P2P + 1 };
+	enum { VFIO_DEVICE_NUM_STATES = VFIO_DEVICE_STATE_PRE_COPY_P2P + 1 };
 	/*
 	 * The coding in this table requires the driver to implement
 	 * FSM arcs:
@@ -1592,25 +1592,59 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 	 *         RUNNING -> STOP
 	 *         STOP -> RUNNING
 	 *
+	 * If precopy is supported then the driver must support these additional
+	 * FSM arcs:
+	 *         RUNNING -> PRE_COPY
+	 *         PRE_COPY -> RUNNING
+	 *         PRE_COPY -> STOP_COPY
+	 * However, if precopy and P2P are supported together then the driver
+	 * must support these additional arcs beyond the P2P arcs above:
+	 *         PRE_COPY -> RUNNING
+	 *         PRE_COPY -> PRE_COPY_P2P
+	 *         PRE_COPY_P2P -> PRE_COPY
+	 *         PRE_COPY_P2P -> RUNNING_P2P
+	 *         PRE_COPY_P2P -> STOP_COPY
+	 *         RUNNING -> PRE_COPY
+	 *         RUNNING_P2P -> PRE_COPY_P2P
+	 *
 	 * If all optional features are supported then the coding will step
 	 * through multiple states for these combination transitions:
+	 *         PRE_COPY -> PRE_COPY_P2P -> STOP_COPY
+	 *         PRE_COPY -> RUNNING -> RUNNING_P2P
+	 *         PRE_COPY -> RUNNING -> RUNNING_P2P -> STOP
+	 *         PRE_COPY -> RUNNING -> RUNNING_P2P -> STOP -> RESUMING
+	 *         PRE_COPY_P2P -> RUNNING_P2P -> RUNNING
+	 *         PRE_COPY_P2P -> RUNNING_P2P -> STOP
+	 *         PRE_COPY_P2P -> RUNNING_P2P -> STOP -> RESUMING
 	 *         RESUMING -> STOP -> RUNNING_P2P
+	 *         RESUMING -> STOP -> RUNNING_P2P -> PRE_COPY_P2P
 	 *         RESUMING -> STOP -> RUNNING_P2P -> RUNNING
+	 *         RESUMING -> STOP -> RUNNING_P2P -> RUNNING -> PRE_COPY
 	 *         RESUMING -> STOP -> STOP_COPY
+	 *         RUNNING -> RUNNING_P2P -> PRE_COPY_P2P
 	 *         RUNNING -> RUNNING_P2P -> STOP
 	 *         RUNNING -> RUNNING_P2P -> STOP -> RESUMING
 	 *         RUNNING -> RUNNING_P2P -> STOP -> STOP_COPY
+	 *         RUNNING_P2P -> RUNNING -> PRE_COPY
 	 *         RUNNING_P2P -> STOP -> RESUMING
 	 *         RUNNING_P2P -> STOP -> STOP_COPY
+	 *         STOP -> RUNNING_P2P -> PRE_COPY_P2P
 	 *         STOP -> RUNNING_P2P -> RUNNING
+	 *         STOP -> RUNNING_P2P -> RUNNING -> PRE_COPY
 	 *         STOP_COPY -> STOP -> RESUMING
 	 *         STOP_COPY -> STOP -> RUNNING_P2P
 	 *         STOP_COPY -> STOP -> RUNNING_P2P -> RUNNING
+	 *
+	 *  The following transitions are blocked:
+	 *         STOP_COPY -> PRE_COPY
+	 *         STOP_COPY -> PRE_COPY_P2P
 	 */
 	static const u8 vfio_from_fsm_table[VFIO_DEVICE_NUM_STATES][VFIO_DEVICE_NUM_STATES] = {
 		[VFIO_DEVICE_STATE_STOP] = {
 			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_RUNNING_P2P,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_RUNNING_P2P,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_RUNNING_P2P,
 			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_STOP_COPY,
 			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_RESUMING,
 			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_RUNNING_P2P,
@@ -1619,14 +1653,38 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 		[VFIO_DEVICE_STATE_RUNNING] = {
 			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_RUNNING_P2P,
 			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_PRE_COPY,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_RUNNING_P2P,
 			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_RUNNING_P2P,
 			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_RUNNING_P2P,
 			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_RUNNING_P2P,
 			[VFIO_DEVICE_STATE_ERROR] = VFIO_DEVICE_STATE_ERROR,
 		},
+		[VFIO_DEVICE_STATE_PRE_COPY] = {
+			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_PRE_COPY,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_PRE_COPY_P2P,
+			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_PRE_COPY_P2P,
+			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_ERROR] = VFIO_DEVICE_STATE_ERROR,
+		},
+		[VFIO_DEVICE_STATE_PRE_COPY_P2P] = {
+			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_RUNNING_P2P,
+			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_RUNNING_P2P,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_PRE_COPY,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_PRE_COPY_P2P,
+			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_STOP_COPY,
+			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_RUNNING_P2P,
+			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_RUNNING_P2P,
+			[VFIO_DEVICE_STATE_ERROR] = VFIO_DEVICE_STATE_ERROR,
+		},
 		[VFIO_DEVICE_STATE_STOP_COPY] = {
 			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_STOP,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_ERROR,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_ERROR,
 			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_STOP_COPY,
 			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_STOP,
@@ -1635,6 +1693,8 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 		[VFIO_DEVICE_STATE_RESUMING] = {
 			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_STOP,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_STOP,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_RESUMING,
 			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_STOP,
@@ -1643,6 +1703,8 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 		[VFIO_DEVICE_STATE_RUNNING_P2P] = {
 			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_RUNNING,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_PRE_COPY_P2P,
 			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_STOP,
 			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_RUNNING_P2P,
@@ -1651,6 +1713,8 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 		[VFIO_DEVICE_STATE_ERROR] = {
 			[VFIO_DEVICE_STATE_STOP] = VFIO_DEVICE_STATE_ERROR,
 			[VFIO_DEVICE_STATE_RUNNING] = VFIO_DEVICE_STATE_ERROR,
+			[VFIO_DEVICE_STATE_PRE_COPY] = VFIO_DEVICE_STATE_ERROR,
+			[VFIO_DEVICE_STATE_PRE_COPY_P2P] = VFIO_DEVICE_STATE_ERROR,
 			[VFIO_DEVICE_STATE_STOP_COPY] = VFIO_DEVICE_STATE_ERROR,
 			[VFIO_DEVICE_STATE_RESUMING] = VFIO_DEVICE_STATE_ERROR,
 			[VFIO_DEVICE_STATE_RUNNING_P2P] = VFIO_DEVICE_STATE_ERROR,
@@ -1658,18 +1722,32 @@ u32 vfio_mig_get_next_state(struct vfio_device *device,
 		},
 	};
 	bool have_p2p = device->migration_flags & VFIO_MIGRATION_P2P;
+	bool have_pre_copy = device->migration_flags & VFIO_MIGRATION_PRE_COPY;
 
 	if (cur_fsm >= ARRAY_SIZE(vfio_from_fsm_table) ||
 	    new_fsm >= ARRAY_SIZE(vfio_from_fsm_table))
 		return VFIO_DEVICE_STATE_ERROR;
 
 	if (!have_p2p && (new_fsm == VFIO_DEVICE_STATE_RUNNING_P2P ||
-			  cur_fsm == VFIO_DEVICE_STATE_RUNNING_P2P))
+			  new_fsm == VFIO_DEVICE_STATE_PRE_COPY_P2P ||
+			  cur_fsm == VFIO_DEVICE_STATE_RUNNING_P2P ||
+			  cur_fsm == VFIO_DEVICE_STATE_PRE_COPY_P2P))
+		return VFIO_DEVICE_STATE_ERROR;
+
+	/*
+	 * PRE_COPY states do not appear as an interior next state, so rejecting
+	 * them here is sufficient.
+	 */
+	if (!have_pre_copy && (new_fsm == VFIO_DEVICE_STATE_PRE_COPY ||
+			       new_fsm == VFIO_DEVICE_STATE_PRE_COPY_P2P ||
+			       cur_fsm == VFIO_DEVICE_STATE_PRE_COPY ||
+			       cur_fsm == VFIO_DEVICE_STATE_PRE_COPY_P2P))
 		return VFIO_DEVICE_STATE_ERROR;
 
 	cur_fsm = vfio_from_fsm_table[cur_fsm][new_fsm];
 	if (!have_p2p) {
-		while (cur_fsm == VFIO_DEVICE_STATE_RUNNING_P2P)
+		while (cur_fsm == VFIO_DEVICE_STATE_RUNNING_P2P ||
+		       cur_fsm == VFIO_DEVICE_STATE_PRE_COPY_P2P)
 			cur_fsm = vfio_from_fsm_table[cur_fsm][new_fsm];
 	}
 	return cur_fsm;
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 69a574ba085e..f853a3539b8b 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -45,7 +45,6 @@ struct vfio_device {
 /**
  * struct vfio_device_ops - VFIO bus driver device callbacks
  *
- * @flags: Global flags from enum vfio_device_ops_flags
  * @open_device: Called when the first file descriptor is opened for this device
  * @close_device: Opposite of open_device
  * @read: Perform read(2) on device file descriptor
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 70c77da5812d..7837fe2ca8de 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -785,12 +785,20 @@ struct vfio_device_feature {
  * VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_P2P means that RUNNING_P2P
  * is supported in addition to the STOP_COPY states.
  *
+ * VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_PRE_COPY means that
+ * PRE_COPY is supported in addition to the STOP_COPY states.
+ *
+ * VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_P2P | VFIO_MIGRATION_PRE_COPY
+ * means that RUNNING_P2P, PRE_COPY and PRE_COPY_P2P are supported
+ * in addition to the STOP_COPY states.
+ *
  * Other combinations of flags have behavior to be defined in the future.
  */
 struct vfio_device_feature_migration {
 	__aligned_u64 flags;
 #define VFIO_MIGRATION_STOP_COPY	(1 << 0)
 #define VFIO_MIGRATION_P2P		(1 << 1)
+#define VFIO_MIGRATION_PRE_COPY		(1 << 2)
 };
 #define VFIO_DEVICE_FEATURE_MIGRATION 1
 
@@ -807,8 +815,13 @@ struct vfio_device_feature_migration {
  *  RESUMING - The device is stopped and is loading a new internal state
  *  ERROR - The device has failed and must be reset
  *
- * And 1 optional state to support VFIO_MIGRATION_P2P:
+ * And optional states to support VFIO_MIGRATION_P2P:
  *  RUNNING_P2P - RUNNING, except the device cannot do peer to peer DMA
+ * And VFIO_MIGRATION_PRE_COPY:
+ *  PRE_COPY - The device is running normally but tracking internal state
+ *             changes
+ * And VFIO_MIGRATION_P2P | VFIO_MIGRATION_PRE_COPY:
+ *  PRE_COPY_P2P - PRE_COPY, except the device cannot do peer to peer DMA
  *
  * The FSM takes actions on the arcs between FSM states. The driver implements
  * the following behavior for the FSM arcs:
@@ -840,20 +853,48 @@ struct vfio_device_feature_migration {
  *
  *   To abort a RESUMING session the device must be reset.
  *
+ * PRE_COPY -> RUNNING
  * RUNNING_P2P -> RUNNING
  *   While in RUNNING the device is fully operational, the device may generate
  *   interrupts, DMA, respond to MMIO, all vfio device regions are functional,
  *   and the device may advance its internal state.
  *
+ *   The PRE_COPY arc will terminate a data transfer session.
+ *
+ * PRE_COPY_P2P -> RUNNING_P2P
  * RUNNING -> RUNNING_P2P
  * STOP -> RUNNING_P2P
  *   While in RUNNING_P2P the device is partially running in the P2P quiescent
  *   state defined below.
  *
+ *   The PRE_COPY arc will terminate a data transfer session.
+ *
+ * RUNNING -> PRE_COPY
+ * RUNNING_P2P -> PRE_COPY_P2P
  * STOP -> STOP_COPY
- *   This arc begin the process of saving the device state and will return a
- *   new data_fd.
+ *   PRE_COPY, PRE_COPY_P2P and STOP_COPY form the "saving group" of states
+ *   which share a data transfer session. Moving between these states alters
+ *   what is streamed in session, but does not terminate or otherwise effect
+ *   the associated fd.
+ *
+ *   These arcs begin the process of saving the device state and will return a
+ *   new data_fd. The migration driver may perform actions such as enabling
+ *   dirty logging of device state when entering PRE_COPY or PER_COPY_P2P.
+ *
+ *   Each arc does not change the device operation, the device remains
+ *   RUNNING, P2P quiesced or in STOP. The STOP_COPY state is described below
+ *   in PRE_COPY_P2P -> STOP_COPY.
+ *
+ * PRE_COPY -> PRE_COPY_P2P
+ *   Entering PRE_COPY_P2P continues all the behaviors of PRE_COPY above.
+ *   However, while in the PRE_COPY_P2P state, the device is partially running
+ *   in the P2P quiescent state defined below, like RUNNING_P2P.
  *
+ * PRE_COPY_P2P -> PRE_COPY
+ *   This arc allows returning the device to a full RUNNING behavior while
+ *   continuing all the behaviors of PRE_COPY.
+ *
+ * PRE_COPY_P2P -> STOP_COPY
  *   While in the STOP_COPY state the device has the same behavior as STOP
  *   with the addition that the data transfers session continues to stream the
  *   migration state. End of stream on the FD indicates the entire device
@@ -871,6 +912,13 @@ struct vfio_device_feature_migration {
  *   internal device state for this arc if required to prepare the device to
  *   receive the migration data.
  *
+ * STOP_COPY -> PRE_COPY
+ * STOP_COPY -> PRE_COPY_P2P
+ *   These arcs are not permitted and return error if requested. Future
+ *   revisions of this API may define behaviors for these arcs, in this case
+ *   support will be discoverable by a new flag in
+ *   VFIO_DEVICE_FEATURE_MIGRATION.
+ *
  * any -> ERROR
  *   ERROR cannot be specified as a device state, however any transition request
  *   can be failed with an errno return and may then move the device_state into
@@ -883,7 +931,7 @@ struct vfio_device_feature_migration {
  * The optional peer to peer (P2P) quiescent state is intended to be a quiescent
  * state for the device for the purposes of managing multiple devices within a
  * user context where peer-to-peer DMA between devices may be active. The
- * RUNNING_P2P states must prevent the device from initiating
+ * RUNNING_P2P and PRE_COPY_P2P states must prevent the device from initiating
  * any new P2P DMA transactions. If the device can identify P2P transactions
  * then it can stop only P2P DMA, otherwise it must stop all DMA. The migration
  * driver must complete any such outstanding operations prior to completing the
@@ -894,6 +942,8 @@ struct vfio_device_feature_migration {
  * above FSM arcs. As there are multiple paths through the FSM arcs the path
  * should be selected based on the following rules:
  *   - Select the shortest path.
+ *   - The path cannot have saving group states as interior arcs, only
+ *     starting/end states.
  * Refer to vfio_mig_get_next_state() for the result of the algorithm.
  *
  * The automatic transit through the FSM arcs that make up the combination
@@ -907,6 +957,9 @@ struct vfio_device_feature_migration {
  * support them. The user can disocver if these states are supported by using
  * VFIO_DEVICE_FEATURE_MIGRATION. By using combination transitions the user can
  * avoid knowing about these optional states if the kernel driver supports them.
+ *
+ * Arcs touching PRE_COPY and PRE_COPY_P2P are removed if support for PRE_COPY
+ * is not present.
  */
 enum vfio_device_mig_state {
 	VFIO_DEVICE_STATE_ERROR = 0,
@@ -915,6 +968,8 @@ enum vfio_device_mig_state {
 	VFIO_DEVICE_STATE_STOP_COPY = 3,
 	VFIO_DEVICE_STATE_RESUMING = 4,
 	VFIO_DEVICE_STATE_RUNNING_P2P = 5,
+	VFIO_DEVICE_STATE_PRE_COPY = 6,
+	VFIO_DEVICE_STATE_PRE_COPY_P2P = 7,
 };
 
 /**
@@ -960,6 +1015,53 @@ struct vfio_device_mig_set_state {
 
 #define VFIO_DEVICE_MIG_SET_STATE _IO(VFIO_TYPE, VFIO_BASE + 21)
 
+/**
+ * VFIO_DEVICE_MIG_PRECOPY - _IO(VFIO_TYPE, VFIO_BASE + 22)
+ *
+ * This ioctl is used in the precopy phase of the migration data transfer. It
+ * returns an estimate of the current data sizes remaining to be transferred.
+ * It allows the user to judge when it is appropriate to leave PRE_COPY for
+ * STOP_COPY.
+ *
+ * initial_bytes reflects the estimated remaining size of any initial mandatory
+ * precopy data transfer. When initial_bytes returns as zero then the initial
+ * phase of the precopy data is completed. Generally initial_bytes should start
+ * out as approximately the entire device state.
+ *
+ * dirty_bytes reflects an estimate for how much more data needs to be
+ * transferred to complete the migration. Generally it should start as zero
+ * and increase as internal state is dirtied.
+ *
+ * Drivers should attempt to return estimates so that initial_bytes +
+ * dirty_bytes matches the amount of data an immediate transition to STOP_COPY
+ * will require to be streamed.
+ *
+ * Drivers have alot of flexability in when and what they transfer during the
+ * PRE_COPY phase, and how they report this from VFIO_DEVICE_MIG_PRECOPY.
+ *
+ * During pre-copy the migration data FD has a temporary "end of stream" that is
+ * reached when both initial_bytes and dirty_byte are zero. For instance, this
+ * may indicate that the device is idle and not currently dirtying any internal
+ * state. When read() is done on this temporary end of stream the kernel driver
+ * should return ENOMSG from read(). Userspace can wait for more data (which may
+ * never come) by using poll.
+ *
+ * Once in STOP_COPY the migration data FD has a permanent end of stream
+ * signaled in the usual way by read() always returning 0 and poll always
+ * returning readable. ENOMSG may not be returned in STOP_COPY. Support
+ * for this ioctl is optional.
+ *
+ * Return: 0 on success, -1 and errno set on failure.
+ */
+struct vfio_device_mig_precopy {
+	__u32 argsz;
+	__u32 flags;
+	__aligned_u64 initial_bytes;
+	__aligned_u64 dirty_bytes;
+};
+
+#define VFIO_DEVICE_MIG_PRECOPY _IO(VFIO_TYPE, VFIO_BASE + 22)
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**
