[dpdk-dev] [PATCH RFC v2 0/3] Thread safe rte_vhost_enqueue_burst().

[dpdk-dev] [PATCH RFC v2 0/3] Thread safe rte_vhost_enqueue_burst().

[Ilya Maximets]

Implementation of rte_vhost_enqueue_burst() based on lockless ring-buffer
algorithm and contains almost all to be thread-safe, but it's not.

This set adds required changes.

First patch in set is a standalone patch that fixes many times discussed
issue with barriers on different architectures.

Second and third adds fixes to make rte_vhost_enqueue_burst thread safe.

version 2:
	* Documentation patch dropped. Other patches of series still
	  may be merged to fix existing issues and keep code in
	  consistent state for the future.
	* buf_vec field of struct vhost_virtqueue marked as deprecated.

Ilya Maximets (3):
  vhost: use SMP barriers instead of compiler ones.
  vhost: make buf vector for scatter RX local.
  vhost: avoid reordering of used->idx and last_used_idx updating.

 doc/guides/rel_notes/deprecation.rst |  1 +
 lib/librte_vhost/rte_virtio_net.h    |  2 +-
 lib/librte_vhost/vhost_rxtx.c        | 67 ++++++++++++++++++++----------------
 3 files changed, 40 insertions(+), 30 deletions(-)

-- 
2.5.0

[dpdk-dev] [PATCH RFC v2 1/3] vhost: use SMP barriers instead of compiler ones.

[Ilya Maximets]

Since commit 4c02e453cc62 ("eal: introduce SMP memory barriers") virtio
uses architecture dependent SMP barriers. vHost should use them too.

Fixes: 4c02e453cc62 ("eal: introduce SMP memory barriers")

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
---
 lib/librte_vhost/vhost_rxtx.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 5e7e5b1..411dd95 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -274,7 +274,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		}
 	}
 
-	rte_compiler_barrier();
+	rte_smp_wmb();
 
 	/* Wait until it's our turn to add our buffer to the used ring. */
 	while (unlikely(vq->last_used_idx != res_base_idx))
@@ -575,7 +575,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 		entry_success = copy_from_mbuf_to_vring(dev, queue_id,
 			res_base_idx, res_cur_idx, pkts[pkt_idx]);
 
-		rte_compiler_barrier();
+		rte_smp_wmb();
 
 		/*
 		 * Wait until it's our turn to add our buffer
@@ -917,7 +917,7 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
 		entry_success++;
 	}
 
-	rte_compiler_barrier();
+	rte_smp_rmb();
 	vq->used->idx += entry_success;
 	/* Kick guest if required. */
 	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
-- 
2.5.0

[dpdk-dev] [PATCH RFC v2 2/3] vhost: make buf vector for scatter RX local.

[Ilya Maximets]

Array of buf_vector's is just an array for temporary storing information
about available descriptors. It used only locally in virtio_dev_merge_rx()
and there is no reason for that array to be shared.

Fix that by allocating local buf_vec inside virtio_dev_merge_rx().
buf_vec field of struct vhost_virtqueue marked as deprecated.

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
---
 doc/guides/rel_notes/deprecation.rst |  1 +
 lib/librte_vhost/rte_virtio_net.h    |  2 +-
 lib/librte_vhost/vhost_rxtx.c        | 45 ++++++++++++++++++------------------
 3 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index e94d4a2..40f350d 100644
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -7,6 +7,7 @@ API and ABI deprecation notices are to be posted here.
 
 Deprecation Notices
 -------------------
+* Field buf_vec of struct vhost_virtqueue have been deprecated.
 
 * The following fields have been deprecated in rte_eth_stats:
   ibadcrc, ibadlen, imcasts, fdirmatch, fdirmiss,
diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 10dcb90..db05d68 100644
--- a/lib/librte_vhost/rte_virtio_net.h
+++ b/lib/librte_vhost/rte_virtio_net.h
@@ -91,7 +91,7 @@ struct vhost_virtqueue {
 	int			kickfd;			/**< Currently unused as polling mode is enabled. */
 	int			enabled;
 	uint64_t		reserved[16];		/**< Reserve some spaces for future extension. */
-	struct buf_vector	buf_vec[BUF_VECTOR_MAX];	/**< for scatter RX. */
+	struct buf_vector       buf_vec[BUF_VECTOR_MAX] __rte_deprecated;        /**< @deprecated Buffer for scatter RX. */
 } __rte_cache_aligned;
 
 
diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 411dd95..9095fb1 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -295,7 +295,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 static inline uint32_t __attribute__((always_inline))
 copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 			uint16_t res_base_idx, uint16_t res_end_idx,
-			struct rte_mbuf *pkt)
+			struct rte_mbuf *pkt, struct buf_vector *buf_vec)
 {
 	uint32_t vec_idx = 0;
 	uint32_t entry_success = 0;
@@ -325,7 +325,7 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 	 */
 	vq = dev->virtqueue[queue_id];
 
-	vb_addr = gpa_to_vva(dev, vq->buf_vec[vec_idx].buf_addr);
+	vb_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
 	vb_hdr_addr = vb_addr;
 
 	/* Prefetch buffer address. */
@@ -345,19 +345,19 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 
 	seg_avail = rte_pktmbuf_data_len(pkt);
 	vb_offset = vq->vhost_hlen;
-	vb_avail = vq->buf_vec[vec_idx].buf_len - vq->vhost_hlen;
+	vb_avail = buf_vec[vec_idx].buf_len - vq->vhost_hlen;
 
 	entry_len = vq->vhost_hlen;
 
 	if (vb_avail == 0) {
 		uint32_t desc_idx =
-			vq->buf_vec[vec_idx].desc_idx;
+			buf_vec[vec_idx].desc_idx;
 
 		if ((vq->desc[desc_idx].flags
 			& VRING_DESC_F_NEXT) == 0) {
 			/* Update used ring with desc information */
 			vq->used->ring[cur_idx & (vq->size - 1)].id
-				= vq->buf_vec[vec_idx].desc_idx;
+				= buf_vec[vec_idx].desc_idx;
 			vq->used->ring[cur_idx & (vq->size - 1)].len
 				= entry_len;
 
@@ -367,12 +367,12 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 		}
 
 		vec_idx++;
-		vb_addr = gpa_to_vva(dev, vq->buf_vec[vec_idx].buf_addr);
+		vb_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
 
 		/* Prefetch buffer address. */
 		rte_prefetch0((void *)(uintptr_t)vb_addr);
 		vb_offset = 0;
-		vb_avail = vq->buf_vec[vec_idx].buf_len;
+		vb_avail = buf_vec[vec_idx].buf_len;
 	}
 
 	cpy_len = RTE_MIN(vb_avail, seg_avail);
@@ -399,11 +399,11 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 			 * entry reach to its end.
 			 * But the segment doesn't complete.
 			 */
-			if ((vq->desc[vq->buf_vec[vec_idx].desc_idx].flags &
+			if ((vq->desc[buf_vec[vec_idx].desc_idx].flags &
 				VRING_DESC_F_NEXT) == 0) {
 				/* Update used ring with desc information */
 				vq->used->ring[cur_idx & (vq->size - 1)].id
-					= vq->buf_vec[vec_idx].desc_idx;
+					= buf_vec[vec_idx].desc_idx;
 				vq->used->ring[cur_idx & (vq->size - 1)].len
 					= entry_len;
 				entry_len = 0;
@@ -413,9 +413,9 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 
 			vec_idx++;
 			vb_addr = gpa_to_vva(dev,
-				vq->buf_vec[vec_idx].buf_addr);
+				buf_vec[vec_idx].buf_addr);
 			vb_offset = 0;
-			vb_avail = vq->buf_vec[vec_idx].buf_len;
+			vb_avail = buf_vec[vec_idx].buf_len;
 			cpy_len = RTE_MIN(vb_avail, seg_avail);
 		} else {
 			/*
@@ -434,7 +434,7 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 					 * from buf_vec.
 					 */
 					uint32_t desc_idx =
-						vq->buf_vec[vec_idx].desc_idx;
+						buf_vec[vec_idx].desc_idx;
 
 					if ((vq->desc[desc_idx].flags &
 						VRING_DESC_F_NEXT) == 0) {
@@ -456,9 +456,9 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 					/* Get next buffer from buf_vec. */
 					vec_idx++;
 					vb_addr = gpa_to_vva(dev,
-						vq->buf_vec[vec_idx].buf_addr);
+						buf_vec[vec_idx].buf_addr);
 					vb_avail =
-						vq->buf_vec[vec_idx].buf_len;
+						buf_vec[vec_idx].buf_len;
 					vb_offset = 0;
 				}
 
@@ -471,7 +471,7 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 				 */
 				/* Update used ring with desc information */
 				vq->used->ring[cur_idx & (vq->size - 1)].id
-					= vq->buf_vec[vec_idx].desc_idx;
+					= buf_vec[vec_idx].desc_idx;
 				vq->used->ring[cur_idx & (vq->size - 1)].len
 					= entry_len;
 				entry_success++;
@@ -485,7 +485,7 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 
 static inline void __attribute__((always_inline))
 update_secure_len(struct vhost_virtqueue *vq, uint32_t id,
-	uint32_t *secure_len, uint32_t *vec_idx)
+	uint32_t *secure_len, uint32_t *vec_idx, struct buf_vector *buf_vec)
 {
 	uint16_t wrapped_idx = id & (vq->size - 1);
 	uint32_t idx = vq->avail->ring[wrapped_idx];
@@ -496,9 +496,9 @@ update_secure_len(struct vhost_virtqueue *vq, uint32_t id,
 	do {
 		next_desc = 0;
 		len += vq->desc[idx].len;
-		vq->buf_vec[vec_id].buf_addr = vq->desc[idx].addr;
-		vq->buf_vec[vec_id].buf_len = vq->desc[idx].len;
-		vq->buf_vec[vec_id].desc_idx = idx;
+		buf_vec[vec_id].buf_addr = vq->desc[idx].addr;
+		buf_vec[vec_id].buf_len = vq->desc[idx].len;
+		buf_vec[vec_id].desc_idx = idx;
 		vec_id++;
 
 		if (vq->desc[idx].flags & VRING_DESC_F_NEXT) {
@@ -523,6 +523,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 	uint16_t avail_idx;
 	uint16_t res_base_idx, res_cur_idx;
 	uint8_t success = 0;
+	struct buf_vector buf_vec[BUF_VECTOR_MAX];
 
 	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_merge_rx()\n",
 		dev->device_fh);
@@ -561,8 +562,8 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 				if (unlikely(res_cur_idx == avail_idx))
 					goto merge_rx_exit;
 
-				update_secure_len(vq, res_cur_idx,
-						  &secure_len, &vec_idx);
+				update_secure_len(vq, res_cur_idx, &secure_len,
+						  &vec_idx, buf_vec);
 				res_cur_idx++;
 			} while (pkt_len > secure_len);
 
@@ -573,7 +574,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 		} while (success == 0);
 
 		entry_success = copy_from_mbuf_to_vring(dev, queue_id,
-			res_base_idx, res_cur_idx, pkts[pkt_idx]);
+			res_base_idx, res_cur_idx, pkts[pkt_idx], buf_vec);
 
 		rte_smp_wmb();
 
-- 
2.5.0

[dpdk-dev] [PATCH RFC v2 3/3] vhost: avoid reordering of used->idx and last_used_idx updating.

[Ilya Maximets]

Calling rte_vhost_enqueue_burst() simultaneously from different threads
for the same queue_id requires additional SMP memory barrier to avoid
reordering of used->idx and last_used_idx updates.

In case of virtio_dev_rx() memory barrier rte_mb() simply moved one
instruction higher.

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
---
 lib/librte_vhost/vhost_rxtx.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 9095fb1..a03f687 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -281,10 +281,13 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		rte_pause();
 
 	*(volatile uint16_t *)&vq->used->idx += count;
-	vq->last_used_idx = res_end_idx;
 
-	/* flush used->idx update before we read avail->flags. */
+	/*
+	 * Flush used->idx update to make it visible to virtio and all other
+	 * threads before allowing to modify it.
+	 */
 	rte_mb();
+	vq->last_used_idx = res_end_idx;
 
 	/* Kick the guest if necessary. */
 	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
@@ -586,19 +589,24 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 			rte_pause();
 
 		*(volatile uint16_t *)&vq->used->idx += entry_success;
+		/*
+		 * Flush used->idx update to make it visible to all
+		 * other threads before allowing to modify it.
+		 */
+		rte_smp_wmb();
+
 		vq->last_used_idx = res_cur_idx;
 	}
 
 merge_rx_exit:
 	if (likely(pkt_idx)) {
-		/* flush used->idx update before we read avail->flags. */
+		/* Flush used->idx update to make it visible to virtio. */
 		rte_mb();
 
 		/* Kick the guest if necessary. */
 		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
 			eventfd_write(vq->callfd, (eventfd_t)1);
 	}
-
 	return pkt_idx;
 }
 
-- 
2.5.0