[dpdk-dev] [RFC PATCH 12/13] support inorder in vhost dequeue path

[Marvin Liu <yong.liu@intel.com>]

When inorder feature bit is negotiated, just update first used
descriptor with last descriptor index. It can reflect all used
descriptors.

Signed-off-by: Marvin Liu <yong.liu@intel.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 0f9292eb0..6bcf565f0 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -31,6 +31,12 @@ rxvq_is_mergeable(struct virtio_net *dev)
 	return dev->features & (1ULL << VIRTIO_NET_F_MRG_RXBUF);
 }
 
+static  __rte_always_inline bool
+virtio_net_is_inorder(struct virtio_net *dev)
+{
+	return dev->features & (1ULL << VIRTIO_F_IN_ORDER);
+}
+
 static bool
 is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
 {
@@ -158,6 +164,35 @@ flush_shadow_used_ring_packed(struct virtio_net *dev,
 	vhost_log_cache_sync(dev, vq);
 }
 
+static __rte_always_inline void
+flush_dequeue_shadow_used_packed_inorder(struct virtio_net *dev,
+				struct vhost_virtqueue *vq)
+{
+	uint16_t head_idx = vq->dequeue_shadow_head;
+	uint16_t head_flags = 0;
+	struct vring_used_elem_packed *last_elem;
+
+	last_elem = &vq->shadow_used_packed[vq->shadow_used_idx - 1];
+	vq->desc_packed[head_idx].id = last_elem->id + last_elem->count - 1;
+
+	if (vq->shadow_used_packed[0].used_wrap_counter)
+		head_flags = VIRTIO_TX_FLAG_PACKED;
+	else
+		head_flags = VIRTIO_TX_WRAP_FLAG_PACKED;
+
+	rte_smp_wmb();
+
+	vq->desc_packed[head_idx].flags = head_flags;
+
+	vhost_log_cache_used_vring(dev, vq,
+				head_idx *
+				sizeof(struct vring_packed_desc),
+				sizeof(struct vring_packed_desc));
+
+	vq->shadow_used_idx = 0;
+	vhost_log_cache_sync(dev, vq);
+}
+
 static __rte_always_inline void
 flush_enqueue_used_packed(struct virtio_net *dev,
 			struct vhost_virtqueue *vq)
@@ -269,6 +304,34 @@ flush_dequeue_shadow_used_packed(struct virtio_net *dev,
 	vhost_log_cache_sync(dev, vq);
 }
 
+static __rte_always_inline void
+flush_used_fast_packed_inorder(struct virtio_net *dev,
+			struct vhost_virtqueue *vq, uint64_t len,
+			uint64_t len1, uint64_t len2, uint64_t len3,
+			uint16_t id, uint16_t flags)
+{
+	vq->desc_packed[vq->last_used_idx].id = id;
+	vq->desc_packed[vq->last_used_idx].len = len;
+	vq->desc_packed[vq->last_used_idx + 1].len = len1;
+	vq->desc_packed[vq->last_used_idx + 2].len = len2;
+	vq->desc_packed[vq->last_used_idx + 3].len = len3;
+
+	rte_smp_wmb();
+	vq->desc_packed[vq->last_used_idx].flags = flags;
+
+	vhost_log_cache_used_vring(dev, vq,
+				vq->last_used_idx *
+				sizeof(struct vring_packed_desc),
+				RTE_CACHE_LINE_SIZE);
+	vhost_log_cache_sync(dev, vq);
+
+	vq->last_used_idx += PACKED_DESC_PER_CACHELINE;
+	if (vq->last_used_idx >= vq->size) {
+		vq->used_wrap_counter ^= 1;
+		vq->last_used_idx -= vq->size;
+	}
+}
+
 /* flags are same when flushing used ring in fast path */
 static __rte_always_inline void
 flush_used_fast_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
@@ -320,8 +383,12 @@ flush_dequeue_fast_used_packed(struct virtio_net *dev,
 		flags = VIRTIO_TX_FLAG_PACKED;
 	else
 		flags = VIRTIO_TX_WRAP_FLAG_PACKED;
-
-	flush_used_fast_packed(dev, vq, 0, 0, 0, 0, id, id1, id2, id3, flags);
+	if (virtio_net_is_inorder(dev))
+		flush_used_fast_packed_inorder(dev, vq, 0, 0, 0, 0, id3,
+					flags);
+	else
+		flush_used_fast_packed(dev, vq, 0, 0, 0, 0, id, id1, id2, id3,
+				flags);
 }
 
 static __rte_always_inline void
@@ -451,7 +518,10 @@ flush_dequeue_shadow_used(struct virtio_net *dev, struct vhost_virtqueue *vq)
 	shadow_count += vq->last_used_idx & 0x3;
 	if ((uint16_t)shadow_count >= (vq->size >> 1)) {
 		do_data_copy_dequeue(vq);
-		flush_dequeue_shadow_used_packed(dev, vq);
+		if (virtio_net_is_inorder(dev))
+			flush_dequeue_shadow_used_packed_inorder(dev, vq);
+		else
+			flush_dequeue_shadow_used_packed(dev, vq);
 		vhost_vring_call_packed(dev, vq);
 	}
 }
-- 
2.17.1