[PATCH V9 19/19] virtio_ring: add in order support

[Jason Wang <jasowang@redhat.com>]

This patch implements in order support for both split virtqueue and
packed virtqueue. Performance could be gained for the device where the
memory access could be expensive (e.g vhost-net or a real PCI device):

Benchmark with KVM guest:

Vhost-net on the host: (pktgen + XDP_DROP):

         in_order=off | in_order=on | +%
    TX:  4.51Mpps     | 5.30Mpps    | +17%
    RX:  3.47Mpps     | 3.61Mpps    | + 4%

Vhost-user(testpmd) on the host: (pktgen/XDP_DROP):

For split virtqueue:

         in_order=off | in_order=on | +%
    TX:  5.60Mpps     | 5.60Mpps    | +0.0%
    RX:  9.16Mpps     | 9.61Mpps    | +4.9%

For packed virtqueue:

         in_order=off | in_order=on | +%
    TX:  5.60Mpps     | 5.70Mpps    | +1.7%
    RX:  10.6Mpps     | 10.8Mpps    | +1.8%

Benchmark also shows no performance impact for in_order=off for queue
size with 256 and 1024.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/virtio/virtio_ring.c | 458 +++++++++++++++++++++++++++++++++--
 1 file changed, 435 insertions(+), 23 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 61884e031b94..9847b23f82ea 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -70,6 +70,8 @@
 enum vq_layout {
 	SPLIT = 0,
 	PACKED,
+	SPLIT_IN_ORDER,
+	PACKED_IN_ORDER,
 	VQ_TYPE_MAX,
 };
 
@@ -80,6 +82,7 @@ struct vring_desc_state_split {
 	 * allocated together. So we won't stress more to the memory allocator.
 	 */
 	struct vring_desc *indir_desc;
+	u32 total_len;			/* Buffer Length */
 };
 
 struct vring_desc_state_packed {
@@ -91,6 +94,7 @@ struct vring_desc_state_packed {
 	struct vring_packed_desc *indir_desc;
 	u16 num;			/* Descriptor list length. */
 	u16 last;			/* The last desc state in a list. */
+	u32 total_len;			/* Buffer Length */
 };
 
 struct vring_desc_extra {
@@ -205,8 +209,24 @@ struct vring_virtqueue {
 
 	enum vq_layout layout;
 
-	/* Head of free buffer list. */
+	/*
+	 * Without IN_ORDER it's the head of free buffer list. With
+	 * IN_ORDER and SPLIT, it's the next available buffer
+	 * index. With IN_ORDER and PACKED, it's unused.
+	 */
 	unsigned int free_head;
+
+	/*
+	 * With IN_ORDER, once we see an in-order batch, this stores
+	 * this last entry, and until we return the last buffer.
+	 * After this, id is set to vq.num to mark it invalid.
+	 * Unused without IN_ORDER.
+	 */
+	struct used_entry {
+		u32 id;
+		u32 len;
+	} batch_last;
+
 	/* Number we've added since last sync. */
 	unsigned int num_added;
 
@@ -218,6 +238,11 @@ struct vring_virtqueue {
 	 */
 	u16 last_used_idx;
 
+	/* With IN_ORDER and SPLIT, last descriptor id we used to
+	 * detach buffer.
+	 */
+	u16 last_used;
+
 	/* Hint for event idx: already triggered no need to disable. */
 	bool event_triggered;
 
@@ -259,7 +284,12 @@ static void vring_free(struct virtqueue *_vq);
 
 static inline bool virtqueue_is_packed(const struct vring_virtqueue *vq)
 {
-	return vq->layout == PACKED;
+	return vq->layout == PACKED || vq->layout == PACKED_IN_ORDER;
+}
+
+static inline bool virtqueue_is_in_order(const struct vring_virtqueue *vq)
+{
+	return vq->layout == SPLIT_IN_ORDER || vq->layout == PACKED_IN_ORDER;
 }
 
 static bool virtqueue_use_indirect(const struct vring_virtqueue *vq,
@@ -469,6 +499,8 @@ static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
 	else
 		vq->last_used_idx = 0;
 
+	vq->last_used = 0;
+
 	vq->event_triggered = false;
 	vq->num_added = 0;
 
@@ -576,6 +608,8 @@ static inline int virtqueue_add_split(struct vring_virtqueue *vq,
 	struct scatterlist *sg;
 	struct vring_desc *desc;
 	unsigned int i, n, avail, descs_used, err_idx, sg_count = 0;
+	/* Total length for in-order */
+	unsigned int total_len = 0;
 	int head;
 	bool indirect;
 
@@ -648,6 +682,7 @@ static inline int virtqueue_add_split(struct vring_virtqueue *vq,
 			 */
 			i = virtqueue_add_desc_split(vq, desc, extra, i, addr,
 						     len, flags ,premapped);
+			total_len += len;
 		}
 	}
 	for (; n < (out_sgs + in_sgs); n++) {
@@ -667,6 +702,7 @@ static inline int virtqueue_add_split(struct vring_virtqueue *vq,
 			 */
 			i = virtqueue_add_desc_split(vq, desc, extra, i, addr,
 						     len, flags, premapped);
+			total_len += len;
 		}
 	}
 
@@ -689,7 +725,12 @@ static inline int virtqueue_add_split(struct vring_virtqueue *vq,
 	vq->vq.num_free -= descs_used;
 
 	/* Update free pointer */
-	if (indirect)
+	if (virtqueue_is_in_order(vq)) {
+		vq->free_head += descs_used;
+		if (vq->free_head >= vq->split.vring.num)
+			vq->free_head -= vq->split.vring.num;
+		vq->split.desc_state[head].total_len = total_len;
+	} else if (indirect)
 		vq->free_head = vq->split.desc_extra[head].next;
 	else
 		vq->free_head = i;
@@ -862,6 +903,14 @@ static bool more_used_split(const struct vring_virtqueue *vq)
 	return virtqueue_poll_split(vq, vq->last_used_idx);
 }
 
+static bool more_used_split_in_order(const struct vring_virtqueue *vq)
+{
+	if (vq->batch_last.id != UINT_MAX)
+		return true;
+
+	return virtqueue_poll_split(vq, vq->last_used_idx);
+}
+
 static void *virtqueue_get_buf_ctx_split(struct vring_virtqueue *vq,
 					 unsigned int *len,
 					 void **ctx)
@@ -919,6 +968,80 @@ static void *virtqueue_get_buf_ctx_split(struct vring_virtqueue *vq,
 	return ret;
 }
 
+static void *virtqueue_get_buf_ctx_split_in_order(struct vring_virtqueue *vq,
+						  unsigned int *len,
+						  void **ctx)
+{
+	void *ret;
+	unsigned int num = vq->split.vring.num;
+	unsigned int num_free = vq->vq.num_free;
+	u16 last_used, last_used_idx;
+
+	START_USE(vq);
+
+	if (unlikely(vq->broken)) {
+		END_USE(vq);
+		return NULL;
+	}
+
+	last_used = vq->last_used & (num - 1);
+	last_used_idx = vq->last_used_idx & (num - 1);
+
+	if (vq->batch_last.id == UINT_MAX) {
+		if (!more_used_split_in_order(vq)) {
+			pr_debug("No more buffers in queue\n");
+			END_USE(vq);
+			return NULL;
+		}
+
+		/*
+		 * Only get used array entries after they have been
+		 * exposed by host.
+		 */
+		virtio_rmb(vq->weak_barriers);
+
+		vq->batch_last.id = virtio32_to_cpu(vq->vq.vdev,
+				    vq->split.vring.used->ring[last_used_idx].id);
+		vq->batch_last.len = virtio32_to_cpu(vq->vq.vdev,
+				     vq->split.vring.used->ring[last_used_idx].len);
+	}
+
+	if (vq->batch_last.id == last_used) {
+		vq->batch_last.id = UINT_MAX;
+		*len = vq->batch_last.len;
+	} else {
+		*len = vq->split.desc_state[last_used].total_len;
+	}
+
+	if (unlikely(last_used >= num)) {
+		BAD_RING(vq, "id %u out of range\n", last_used);
+		return NULL;
+	}
+	if (unlikely(!vq->split.desc_state[last_used].data)) {
+		BAD_RING(vq, "id %u is not a head!\n", last_used);
+		return NULL;
+	}
+
+	/* detach_buf_split clears data, so grab it now. */
+	ret = vq->split.desc_state[last_used].data;
+	detach_buf_split_in_order(vq, last_used, ctx);
+
+	vq->last_used_idx++;
+	vq->last_used += (vq->vq.num_free - num_free);
+	/* If we expect an interrupt for the next entry, tell host
+	 * by writing event index and flush out the write before
+	 * the read in the next get_buf call. */
+	if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT))
+		virtio_store_mb(vq->weak_barriers,
+				&vring_used_event(&vq->split.vring),
+				cpu_to_virtio16(vq->vq.vdev, vq->last_used_idx));
+
+	LAST_ADD_TIME_INVALID(vq);
+
+	END_USE(vq);
+	return ret;
+}
+
 static void virtqueue_disable_cb_split(struct vring_virtqueue *vq)
 {
 	if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
@@ -1012,7 +1135,10 @@ static void *virtqueue_detach_unused_buf_split(struct vring_virtqueue *vq)
 			continue;
 		/* detach_buf_split clears data, so grab it now. */
 		buf = vq->split.desc_state[i].data;
-		detach_buf_split(vq, i, NULL);
+		if (virtqueue_is_in_order(vq))
+			detach_buf_split_in_order(vq, i, NULL);
+		else
+			detach_buf_split(vq, i, NULL);
 		vq->split.avail_idx_shadow--;
 		vq->split.vring.avail->idx = cpu_to_virtio16(vq->vq.vdev,
 				vq->split.avail_idx_shadow);
@@ -1075,6 +1201,7 @@ static void virtqueue_vring_attach_split(struct vring_virtqueue *vq,
 
 	/* Put everything in free lists. */
 	vq->free_head = 0;
+	vq->batch_last.id = UINT_MAX;
 }
 
 static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_split)
@@ -1186,7 +1313,6 @@ static struct virtqueue *__vring_new_virtqueue_split(unsigned int index,
 	if (!vq)
 		return NULL;
 
-	vq->layout = SPLIT;
 	vq->vq.callback = callback;
 	vq->vq.vdev = vdev;
 	vq->vq.name = name;
@@ -1206,6 +1332,8 @@ static struct virtqueue *__vring_new_virtqueue_split(unsigned int index,
 	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
 		!context;
 	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+	vq->layout = virtio_has_feature(vdev, VIRTIO_F_IN_ORDER) ?
+		     SPLIT_IN_ORDER : SPLIT;
 
 	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
 		vq->weak_barriers = false;
@@ -1363,13 +1491,14 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 					 unsigned int in_sgs,
 					 void *data,
 					 bool premapped,
-					 gfp_t gfp)
+					 gfp_t gfp,
+					 u16 id)
 {
 	struct vring_desc_extra *extra;
 	struct vring_packed_desc *desc;
 	struct scatterlist *sg;
-	unsigned int i, n, err_idx, len;
-	u16 head, id;
+	unsigned int i, n, err_idx, len, total_len = 0;
+	u16 head;
 	dma_addr_t addr;
 
 	head = vq->packed.next_avail_idx;
@@ -1387,8 +1516,6 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 	}
 
 	i = 0;
-	id = vq->free_head;
-	BUG_ON(id == vq->packed.vring.num);
 
 	for (n = 0; n < out_sgs + in_sgs; n++) {
 		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
@@ -1408,6 +1535,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 				extra[i].flags = n < out_sgs ?  0 : VRING_DESC_F_WRITE;
 			}
 
+			total_len += len;
 			i++;
 		}
 	}
@@ -1454,13 +1582,15 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 				1 << VRING_PACKED_DESC_F_USED;
 	}
 	vq->packed.next_avail_idx = n;
-	vq->free_head = vq->packed.desc_extra[id].next;
+	if (!virtqueue_is_in_order(vq))
+		vq->free_head = vq->packed.desc_extra[id].next;
 
 	/* Store token and indirect buffer state. */
 	vq->packed.desc_state[id].num = 1;
 	vq->packed.desc_state[id].data = data;
 	vq->packed.desc_state[id].indir_desc = desc;
 	vq->packed.desc_state[id].last = id;
+	vq->packed.desc_state[id].total_len = total_len;
 
 	vq->num_added += 1;
 
@@ -1513,8 +1643,11 @@ static inline int virtqueue_add_packed(struct vring_virtqueue *vq,
 	BUG_ON(total_sg == 0);
 
 	if (virtqueue_use_indirect(vq, total_sg)) {
+		id = vq->free_head;
+		BUG_ON(id == vq->packed.vring.num);
 		err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
-						    in_sgs, data, premapped, gfp);
+						    in_sgs, data, premapped,
+						    gfp, id);
 		if (err != -ENOMEM) {
 			END_USE(vq);
 			return err;
@@ -1635,6 +1768,156 @@ static inline int virtqueue_add_packed(struct vring_virtqueue *vq,
 	return -EIO;
 }
 
+static inline int virtqueue_add_packed_in_order(struct vring_virtqueue *vq,
+						struct scatterlist *sgs[],
+						unsigned int total_sg,
+						unsigned int out_sgs,
+						unsigned int in_sgs,
+						void *data,
+						void *ctx,
+						bool premapped,
+						gfp_t gfp)
+{
+	struct vring_packed_desc *desc;
+	struct scatterlist *sg;
+	unsigned int i, n, sg_count, err_idx, total_len = 0;
+	__le16 head_flags, flags;
+	u16 head, avail_used_flags;
+	int err;
+
+	START_USE(vq);
+
+	BUG_ON(data == NULL);
+	BUG_ON(ctx && vq->indirect);
+
+	if (unlikely(vq->broken)) {
+		END_USE(vq);
+		return -EIO;
+	}
+
+	LAST_ADD_TIME_UPDATE(vq);
+
+	BUG_ON(total_sg == 0);
+
+	if (virtqueue_use_indirect(vq, total_sg)) {
+		err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
+						    in_sgs, data, premapped, gfp,
+						    vq->packed.next_avail_idx);
+		if (err != -ENOMEM) {
+			END_USE(vq);
+			return err;
+		}
+
+		/* fall back on direct */
+	}
+
+	head = vq->packed.next_avail_idx;
+	avail_used_flags = vq->packed.avail_used_flags;
+
+	WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect);
+
+	desc = vq->packed.vring.desc;
+	i = head;
+
+	if (unlikely(vq->vq.num_free < total_sg)) {
+		pr_debug("Can't add buf len %i - avail = %i\n",
+			 total_sg, vq->vq.num_free);
+		END_USE(vq);
+		return -ENOSPC;
+	}
+
+	sg_count = 0;
+	for (n = 0; n < out_sgs + in_sgs; n++) {
+		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+			dma_addr_t addr;
+			u32 len;
+
+			flags = 0;
+			if (++sg_count != total_sg)
+				flags |= cpu_to_le16(VRING_DESC_F_NEXT);
+			if (n >= out_sgs)
+				flags |= cpu_to_le16(VRING_DESC_F_WRITE);
+
+			if (vring_map_one_sg(vq, sg, n < out_sgs ?
+					     DMA_TO_DEVICE : DMA_FROM_DEVICE,
+					     &addr, &len, premapped))
+				goto unmap_release;
+
+			flags |= cpu_to_le16(vq->packed.avail_used_flags);
+
+			if (i == head)
+				head_flags = flags;
+			else
+				desc[i].flags = flags;
+
+			desc[i].addr = cpu_to_le64(addr);
+			desc[i].len = cpu_to_le32(len);
+			desc[i].id = cpu_to_le16(head);
+
+			if (unlikely(vq->use_map_api)) {
+				vq->packed.desc_extra[i].addr = premapped ?
+				      DMA_MAPPING_ERROR: addr;
+				vq->packed.desc_extra[i].len = len;
+				vq->packed.desc_extra[i].flags =
+					le16_to_cpu(flags);
+			}
+
+			if ((unlikely(++i >= vq->packed.vring.num))) {
+				i = 0;
+				vq->packed.avail_used_flags ^=
+					1 << VRING_PACKED_DESC_F_AVAIL |
+					1 << VRING_PACKED_DESC_F_USED;
+				vq->packed.avail_wrap_counter ^= 1;
+			}
+
+			total_len += len;
+		}
+	}
+
+	/* We're using some buffers from the free list. */
+	vq->vq.num_free -= total_sg;
+
+	/* Update free pointer */
+	vq->packed.next_avail_idx = i;
+
+	/* Store token. */
+	vq->packed.desc_state[head].num = total_sg;
+	vq->packed.desc_state[head].data = data;
+	vq->packed.desc_state[head].indir_desc = ctx;
+	vq->packed.desc_state[head].total_len = total_len;
+
+	/*
+	 * A driver MUST NOT make the first descriptor in the list
+	 * available before all subsequent descriptors comprising
+	 * the list are made available.
+	 */
+	virtio_wmb(vq->weak_barriers);
+	vq->packed.vring.desc[head].flags = head_flags;
+	vq->num_added += total_sg;
+
+	pr_debug("Added buffer head %i to %p\n", head, vq);
+	END_USE(vq);
+
+	return 0;
+
+unmap_release:
+	err_idx = i;
+	i = head;
+	vq->packed.avail_used_flags = avail_used_flags;
+
+	for (n = 0; n < total_sg; n++) {
+		if (i == err_idx)
+			break;
+		vring_unmap_extra_packed(vq, &vq->packed.desc_extra[i]);
+		i++;
+		if (i >= vq->packed.vring.num)
+			i = 0;
+	}
+
+	END_USE(vq);
+	return -EIO;
+}
+
 static bool virtqueue_kick_prepare_packed(struct vring_virtqueue *vq)
 {
 	u16 new, old, off_wrap, flags, wrap_counter, event_idx;
@@ -1796,10 +2079,82 @@ static void update_last_used_idx_packed(struct vring_virtqueue *vq,
 				cpu_to_le16(vq->last_used_idx));
 }
 
+static bool more_used_packed_in_order(const struct vring_virtqueue *vq)
+{
+	if (vq->batch_last.id != UINT_MAX)
+		return true;
+
+	return virtqueue_poll_packed(vq, READ_ONCE(vq->last_used_idx));
+}
+
+static void *virtqueue_get_buf_ctx_packed_in_order(struct vring_virtqueue *vq,
+						   unsigned int *len,
+						   void **ctx)
+{
+	unsigned int num = vq->packed.vring.num;
+	u16 last_used, last_used_idx;
+	bool used_wrap_counter;
+	void *ret;
+
+	START_USE(vq);
+
+	if (unlikely(vq->broken)) {
+		END_USE(vq);
+		return NULL;
+	}
+
+	last_used_idx = vq->last_used_idx;
+	used_wrap_counter = packed_used_wrap_counter(last_used_idx);
+	last_used = packed_last_used(last_used_idx);
+
+	if (vq->batch_last.id == UINT_MAX) {
+		if (!more_used_packed_in_order(vq)) {
+			pr_debug("No more buffers in queue\n");
+			END_USE(vq);
+			return NULL;
+		}
+		/* Only get used elements after they have been exposed by host. */
+		virtio_rmb(vq->weak_barriers);
+		vq->batch_last.id =
+			le16_to_cpu(vq->packed.vring.desc[last_used].id);
+		vq->batch_last.len =
+			le32_to_cpu(vq->packed.vring.desc[last_used].len);
+	}
+
+	if (vq->batch_last.id == last_used) {
+		vq->batch_last.id = UINT_MAX;
+		*len = vq->batch_last.len;
+	} else {
+		*len = vq->packed.desc_state[last_used].total_len;
+	}
+
+	if (unlikely(last_used >= num)) {
+		BAD_RING(vq, "id %u out of range\n", last_used);
+		return NULL;
+	}
+	if (unlikely(!vq->packed.desc_state[last_used].data)) {
+		BAD_RING(vq, "id %u is not a head!\n", last_used);
+		return NULL;
+	}
+
+	/* detach_buf_packed clears data, so grab it now. */
+	ret = vq->packed.desc_state[last_used].data;
+	detach_buf_packed_in_order(vq, last_used, ctx);
+
+	update_last_used_idx_packed(vq, last_used, last_used,
+				    used_wrap_counter);
+
+	LAST_ADD_TIME_INVALID(vq);
+
+	END_USE(vq);
+	return ret;
+}
+
 static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq,
 					  unsigned int *len,
 					  void **ctx)
 {
+	unsigned int num = vq->packed.vring.num;
 	u16 last_used, id, last_used_idx;
 	bool used_wrap_counter;
 	void *ret;
@@ -1826,7 +2181,7 @@ static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq,
 	id = le16_to_cpu(vq->packed.vring.desc[last_used].id);
 	*len = le32_to_cpu(vq->packed.vring.desc[last_used].len);
 
-	if (unlikely(id >= vq->packed.vring.num)) {
+	if (unlikely(id >= num)) {
 		BAD_RING(vq, "id %u out of range\n", id);
 		return NULL;
 	}
@@ -1967,7 +2322,10 @@ static void *virtqueue_detach_unused_buf_packed(struct vring_virtqueue *vq)
 			continue;
 		/* detach_buf clears data, so grab it now. */
 		buf = vq->packed.desc_state[i].data;
-		detach_buf_packed(vq, i, NULL);
+		if (virtqueue_is_in_order(vq))
+			detach_buf_packed_in_order(vq, i, NULL);
+		else
+			detach_buf_packed(vq, i, NULL);
 		END_USE(vq);
 		return buf;
 	}
@@ -1993,6 +2351,8 @@ static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num)
 	for (i = 0; i < num - 1; i++)
 		desc_extra[i].next = i + 1;
 
+	desc_extra[num - 1].next = 0;
+
 	return desc_extra;
 }
 
@@ -2124,10 +2484,17 @@ static void virtqueue_vring_attach_packed(struct vring_virtqueue *vq,
 {
 	vq->packed = *vring_packed;
 
-	/* Put everything in free lists. */
-	vq->free_head = 0;
+	if (virtqueue_is_in_order(vq)) {
+		vq->batch_last.id = UINT_MAX;
+	} else {
+		/*
+		 * Put everything in free lists. Note that
+		 * next_avail_idx is sufficient with IN_ORDER so
+		 * free_head is unused.
+		 */
+		vq->free_head = 0;
+	}
 }
-
 static void virtqueue_reset_packed(struct vring_virtqueue *vq)
 {
 	memset(vq->packed.vring.device, 0, vq->packed.event_size_in_bytes);
@@ -2172,13 +2539,14 @@ static struct virtqueue *__vring_new_virtqueue_packed(unsigned int index,
 #else
 	vq->broken = false;
 #endif
-	vq->layout = PACKED;
 	vq->map = map;
 	vq->use_map_api = vring_use_map_api(vdev);
 
 	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
 		!context;
 	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+	vq->layout = virtio_has_feature(vdev, VIRTIO_F_IN_ORDER) ?
+		     PACKED_IN_ORDER : PACKED;
 
 	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
 		vq->weak_barriers = false;
@@ -2288,9 +2656,39 @@ static const struct virtqueue_ops packed_ops = {
 	.reset = virtqueue_reset_packed,
 };
 
+static const struct virtqueue_ops split_in_order_ops = {
+	.add = virtqueue_add_split,
+	.get = virtqueue_get_buf_ctx_split_in_order,
+	.kick_prepare = virtqueue_kick_prepare_split,
+	.disable_cb = virtqueue_disable_cb_split,
+	.enable_cb_delayed = virtqueue_enable_cb_delayed_split,
+	.enable_cb_prepare = virtqueue_enable_cb_prepare_split,
+	.poll = virtqueue_poll_split,
+	.detach_unused_buf = virtqueue_detach_unused_buf_split,
+	.more_used = more_used_split_in_order,
+	.resize = virtqueue_resize_split,
+	.reset = virtqueue_reset_split,
+};
+
+static const struct virtqueue_ops packed_in_order_ops = {
+	.add = virtqueue_add_packed_in_order,
+	.get = virtqueue_get_buf_ctx_packed_in_order,
+	.kick_prepare = virtqueue_kick_prepare_packed,
+	.disable_cb = virtqueue_disable_cb_packed,
+	.enable_cb_delayed = virtqueue_enable_cb_delayed_packed,
+	.enable_cb_prepare = virtqueue_enable_cb_prepare_packed,
+	.poll = virtqueue_poll_packed,
+	.detach_unused_buf = virtqueue_detach_unused_buf_packed,
+	.more_used = more_used_packed_in_order,
+	.resize = virtqueue_resize_packed,
+	.reset = virtqueue_reset_packed,
+};
+
 static const struct virtqueue_ops *const all_ops[VQ_TYPE_MAX] = {
 	[SPLIT] = &split_ops,
-	[PACKED] = &packed_ops
+	[PACKED] = &packed_ops,
+	[SPLIT_IN_ORDER] = &split_in_order_ops,
+	[PACKED_IN_ORDER] = &packed_in_order_ops,
 };
 
 static int virtqueue_disable_and_recycle(struct virtqueue *_vq,
@@ -2346,6 +2744,12 @@ static int virtqueue_enable_after_reset(struct virtqueue *_vq)
 	case PACKED:							\
 		ret = all_ops[PACKED]->op(vq, ##__VA_ARGS__);		\
 		break;							\
+	case SPLIT_IN_ORDER:						\
+		ret = all_ops[SPLIT_IN_ORDER]->op(vq, ##__VA_ARGS__);	\
+		break;							\
+	case PACKED_IN_ORDER:						\
+		ret = all_ops[PACKED_IN_ORDER]->op(vq, ##__VA_ARGS__);	\
+		break;							\
 	default:							\
 		BUG();							\
 		break;							\
@@ -2362,10 +2766,16 @@ static int virtqueue_enable_after_reset(struct virtqueue *_vq)
 	case PACKED:					\
 		all_ops[PACKED]->op(vq, ##__VA_ARGS__);	\
 		break;					\
-	default:					\
-		BUG();					\
-		break;					\
-	}						\
+	case SPLIT_IN_ORDER:						\
+		all_ops[SPLIT_IN_ORDER]->op(vq, ##__VA_ARGS__);	\
+		break;							\
+	case PACKED_IN_ORDER:						\
+		all_ops[PACKED_IN_ORDER]->op(vq, ##__VA_ARGS__);	\
+		break;							\
+	default:							\
+		BUG();							\
+		break;							\
+	}								\
 })
 
 static inline int virtqueue_add(struct virtqueue *_vq,
@@ -3081,6 +3491,8 @@ void vring_transport_features(struct virtio_device *vdev)
 			break;
 		case VIRTIO_F_NOTIFICATION_DATA:
 			break;
+		case VIRTIO_F_IN_ORDER:
+			break;
 		default:
 			/* We don't understand this bit. */
 			__virtio_clear_bit(vdev, i);
-- 
2.31.1