[dpdk-dev] [PATCH] vhost: introduce rte_vhost_vring_call()

Stefan Hajnoczi stefanha at redhat.com
Thu Dec 21 17:41:28 CET 2017


Users of librte_vhost currently implement the vring call operation
themselves.  Each caller performs the operation slightly differently.

This patch introduces a new librte_vhost API called
rte_vhost_vring_call() that performs the operation so that vhost-user
applications don't have to duplicate it.

Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 lib/librte_vhost/rte_vhost.h           | 15 +++++++++++++++
 examples/vhost/virtio_net.c            | 11 ++---------
 examples/vhost_scsi/vhost_scsi.c       |  6 +++---
 lib/librte_vhost/vhost.c               | 27 +++++++++++++++++++++++++++
 lib/librte_vhost/virtio_net.c          | 29 ++++++-----------------------
 lib/librte_vhost/rte_vhost_version.map |  7 +++++++
 6 files changed, 60 insertions(+), 35 deletions(-)

diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
index fe5c94c69..dde0eeb03 100644
--- a/lib/librte_vhost/rte_vhost.h
+++ b/lib/librte_vhost/rte_vhost.h
@@ -85,7 +85,9 @@ struct rte_vhost_vring {
 	struct vring_used	*used;
 	uint64_t		log_guest_addr;
 
+	/** Deprecated, use rte_vhost_vring_call() instead. */
 	int			callfd;
+
 	int			kickfd;
 	uint16_t		size;
 };
@@ -435,6 +437,19 @@ int rte_vhost_get_mem_table(int vid, struct rte_vhost_memory **mem);
 int rte_vhost_get_vhost_vring(int vid, uint16_t vring_idx,
 			      struct rte_vhost_vring *vring);
 
+/**
+ * Notify the guest that used descriptors have been added to the vring.  This
+ * function acts as a memory barrier.
+ *
+ * @param vid
+ *  vhost device ID
+ * @param vring_idx
+ *  vring index
+ * @return
+ *  0 on success, -1 on failure
+ */
+int rte_vhost_vring_call(int vid, uint16_t vring_idx);
+
 /**
  * Get vhost RX queue avail count.
  *
diff --git a/examples/vhost/virtio_net.c b/examples/vhost/virtio_net.c
index 1ab57f526..252c5b8ce 100644
--- a/examples/vhost/virtio_net.c
+++ b/examples/vhost/virtio_net.c
@@ -207,13 +207,8 @@ vs_enqueue_pkts(struct vhost_dev *dev, uint16_t queue_id,
 	*(volatile uint16_t *)&vr->used->idx += count;
 	queue->last_used_idx += count;
 
-	/* flush used->idx update before we read avail->flags. */
-	rte_mb();
+	rte_vhost_vring_call(dev->vid, queue_id);
 
-	/* Kick the guest if necessary. */
-	if (!(vr->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-			&& (vr->callfd >= 0))
-		eventfd_write(vr->callfd, (eventfd_t)1);
 	return count;
 }
 
@@ -396,9 +391,7 @@ vs_dequeue_pkts(struct vhost_dev *dev, uint16_t queue_id,
 
 	vr->used->idx += i;
 
-	if (!(vr->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-			&& (vr->callfd >= 0))
-		eventfd_write(vr->callfd, (eventfd_t)1);
+	rte_vhost_vring_call(dev->vid, queue_id);
 
 	return i;
 }
diff --git a/examples/vhost_scsi/vhost_scsi.c b/examples/vhost_scsi/vhost_scsi.c
index b4f1f8d27..e30e61f6d 100644
--- a/examples/vhost_scsi/vhost_scsi.c
+++ b/examples/vhost_scsi/vhost_scsi.c
@@ -110,7 +110,7 @@ descriptor_is_wr(struct vring_desc *cur_desc)
 }
 
 static void
-submit_completion(struct vhost_scsi_task *task)
+submit_completion(struct vhost_scsi_task *task, uint32_t q_idx)
 {
 	struct rte_vhost_vring *vq;
 	struct vring_used *used;
@@ -131,7 +131,7 @@ submit_completion(struct vhost_scsi_task *task)
 	/* Send an interrupt back to the guest VM so that it knows
 	 * a completion is ready to be processed.
 	 */
-	eventfd_write(vq->callfd, (eventfd_t)1);
+	rte_vhost_vring_call(task->bdev->vid, q_idx);
 }
 
 static void
@@ -263,7 +263,7 @@ process_requestq(struct vhost_scsi_ctrlr *ctrlr, uint32_t q_idx)
 			task->resp->status = 0;
 			task->resp->resid = 0;
 		}
-		submit_completion(task);
+		submit_completion(task, q_idx);
 		rte_free(task);
 	}
 }
diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 4f8b73a09..0d269f12a 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -519,6 +519,33 @@ rte_vhost_get_vhost_vring(int vid, uint16_t vring_idx,
 	return 0;
 }
 
+int
+rte_vhost_vring_call(int vid, uint16_t vring_idx)
+{
+	struct virtio_net *dev;
+	struct vhost_virtqueue *vq;
+
+	dev = get_device(vid);
+	if (!dev)
+		return -1;
+
+	if (vring_idx >= VHOST_MAX_VRING)
+		return -1;
+
+	vq = dev->virtqueue[vring_idx];
+	if (!vq)
+		return -1;
+
+	/* flush used->idx update before we read avail->flags. */
+	rte_mb();
+
+	/* Kick the guest if necessary. */
+	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
+			&& (vq->callfd >= 0))
+		eventfd_write(vq->callfd, (eventfd_t)1);
+	return 0;
+}
+
 uint16_t
 rte_vhost_avail_entries(int vid, uint16_t queue_id)
 {
diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 3c6f1a531..27efae788 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -408,13 +408,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		offsetof(struct vring_used, idx),
 		sizeof(vq->used->idx));
 
-	/* flush used->idx update before we read avail->flags. */
-	rte_mb();
-
-	/* Kick the guest if necessary. */
-	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-			&& (vq->callfd >= 0))
-		eventfd_write(vq->callfd, (eventfd_t)1);
+	rte_vhost_vring_call(dev->vid, queue_id);
 out:
 	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
 		vhost_user_iotlb_rd_unlock(vq);
@@ -701,14 +695,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 
 	if (likely(vq->shadow_used_idx)) {
 		flush_shadow_used_ring(dev, vq);
-
-		/* flush used->idx update before we read avail->flags. */
-		rte_mb();
-
-		/* Kick the guest if necessary. */
-		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-				&& (vq->callfd >= 0))
-			eventfd_write(vq->callfd, (eventfd_t)1);
+		rte_vhost_vring_call(dev->vid, queue_id);
 	}
 
 out:
@@ -1095,7 +1082,7 @@ update_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
 static __rte_always_inline void
 update_used_idx(struct virtio_net *dev, struct vhost_virtqueue *vq,
-		uint32_t count)
+		uint16_t queue_id, uint32_t count)
 {
 	if (unlikely(count == 0))
 		return;
@@ -1106,11 +1093,7 @@ update_used_idx(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	vq->used->idx += count;
 	vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
 			sizeof(vq->used->idx));
-
-	/* Kick guest if required. */
-	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-			&& (vq->callfd >= 0))
-		eventfd_write(vq->callfd, (eventfd_t)1);
+	rte_vhost_vring_call(dev->vid, queue_id);
 }
 
 static __rte_always_inline struct zcopy_mbuf *
@@ -1213,7 +1196,7 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
 			}
 		}
 
-		update_used_idx(dev, vq, nr_updated);
+		update_used_idx(dev, vq, queue_id, nr_updated);
 	}
 
 	/*
@@ -1349,7 +1332,7 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
 	if (likely(dev->dequeue_zero_copy == 0)) {
 		do_data_copy_dequeue(vq);
 		vq->last_used_idx += i;
-		update_used_idx(dev, vq, i);
+		update_used_idx(dev, vq, queue_id, i);
 	}
 
 out:
diff --git a/lib/librte_vhost/rte_vhost_version.map b/lib/librte_vhost/rte_vhost_version.map
index 1e7049535..b30187601 100644
--- a/lib/librte_vhost/rte_vhost_version.map
+++ b/lib/librte_vhost/rte_vhost_version.map
@@ -52,3 +52,10 @@ DPDK_17.08 {
 	rte_vhost_rx_queue_count;
 
 } DPDK_17.05;
+
+EXPERIMENTAL {
+	global:
+
+	rte_vhost_vring_call;
+
+} DPDK_17.08
-- 
2.14.3



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