Imported Upstream version 16.07-rc1
[deb_dpdk.git] / lib / librte_vhost / vhost_rxtx.c
index 750821a..15ca956 100644 (file)
@@ -126,10 +126,10 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
 }
 
 static inline void
-copy_virtio_net_hdr(struct vhost_virtqueue *vq, uint64_t desc_addr,
+copy_virtio_net_hdr(struct virtio_net *dev, uint64_t desc_addr,
                    struct virtio_net_hdr_mrg_rxbuf hdr)
 {
-       if (vq->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf))
+       if (dev->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf))
                *(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr = hdr;
        else
                *(struct virtio_net_hdr *)(uintptr_t)desc_addr = hdr.hdr;
@@ -137,7 +137,7 @@ copy_virtio_net_hdr(struct vhost_virtqueue *vq, uint64_t desc_addr,
 
 static inline int __attribute__((always_inline))
 copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
-                 struct rte_mbuf *m, uint16_t desc_idx, uint32_t *copied)
+                 struct rte_mbuf *m, uint16_t desc_idx)
 {
        uint32_t desc_avail, desc_offset;
        uint32_t mbuf_avail, mbuf_offset;
@@ -147,21 +147,20 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
        struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
 
        desc = &vq->desc[desc_idx];
-       if (unlikely(desc->len < vq->vhost_hlen))
+       if (unlikely(desc->len < dev->vhost_hlen))
                return -1;
 
        desc_addr = gpa_to_vva(dev, desc->addr);
        rte_prefetch0((void *)(uintptr_t)desc_addr);
 
        virtio_enqueue_offload(m, &virtio_hdr.hdr);
-       copy_virtio_net_hdr(vq, desc_addr, virtio_hdr);
-       vhost_log_write(dev, desc->addr, vq->vhost_hlen);
-       PRINT_PACKET(dev, (uintptr_t)desc_addr, vq->vhost_hlen, 0);
+       copy_virtio_net_hdr(dev, desc_addr, virtio_hdr);
+       vhost_log_write(dev, desc->addr, dev->vhost_hlen);
+       PRINT_PACKET(dev, (uintptr_t)desc_addr, dev->vhost_hlen, 0);
 
-       desc_offset = vq->vhost_hlen;
-       desc_avail  = desc->len - vq->vhost_hlen;
+       desc_offset = dev->vhost_hlen;
+       desc_avail  = desc->len - dev->vhost_hlen;
 
-       *copied = rte_pktmbuf_pkt_len(m);
        mbuf_avail  = rte_pktmbuf_data_len(m);
        mbuf_offset = 0;
        while (mbuf_avail != 0 || m->next != NULL) {
@@ -205,49 +204,6 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
        return 0;
 }
 
-/*
- * As many data cores may want to access available buffers
- * they need to be reserved.
- */
-static inline uint32_t
-reserve_avail_buf(struct vhost_virtqueue *vq, uint32_t count,
-                 uint16_t *start, uint16_t *end)
-{
-       uint16_t res_start_idx;
-       uint16_t res_end_idx;
-       uint16_t avail_idx;
-       uint16_t free_entries;
-       int success;
-
-       count = RTE_MIN(count, (uint32_t)MAX_PKT_BURST);
-
-again:
-       res_start_idx = vq->last_used_idx_res;
-       avail_idx = *((volatile uint16_t *)&vq->avail->idx);
-
-       free_entries = avail_idx - res_start_idx;
-       count = RTE_MIN(count, free_entries);
-       if (count == 0)
-               return 0;
-
-       res_end_idx = res_start_idx + count;
-
-       /*
-        * update vq->last_used_idx_res atomically; try again if failed.
-        *
-        * TODO: Allow to disable cmpset if no concurrency in application.
-        */
-       success = rte_atomic16_cmpset(&vq->last_used_idx_res,
-                                     res_start_idx, res_end_idx);
-       if (unlikely(!success))
-               goto again;
-
-       *start = res_start_idx;
-       *end   = res_end_idx;
-
-       return count;
-}
-
 /**
  * This function adds buffers to the virtio devices RX virtqueue. Buffers can
  * be received from the physical port or from another virtio device. A packet
@@ -260,15 +216,15 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
              struct rte_mbuf **pkts, uint32_t count)
 {
        struct vhost_virtqueue *vq;
-       uint16_t res_start_idx, res_end_idx;
+       uint16_t avail_idx, free_entries, start_idx;
        uint16_t desc_indexes[MAX_PKT_BURST];
+       uint16_t used_idx;
        uint32_t i;
 
-       LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_rx()\n", dev->device_fh);
+       LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
        if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->virt_qp_nb))) {
-               RTE_LOG(ERR, VHOST_DATA,
-                       "%s (%"PRIu64"): virtqueue idx:%d invalid.\n",
-                       __func__, dev->device_fh, queue_id);
+               RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
+                       dev->vid, __func__, queue_id);
                return 0;
        }
 
@@ -276,38 +232,43 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
        if (unlikely(vq->enabled == 0))
                return 0;
 
-       count = reserve_avail_buf(vq, count, &res_start_idx, &res_end_idx);
+       avail_idx = *((volatile uint16_t *)&vq->avail->idx);
+       start_idx = vq->last_used_idx;
+       free_entries = avail_idx - start_idx;
+       count = RTE_MIN(count, free_entries);
+       count = RTE_MIN(count, (uint32_t)MAX_PKT_BURST);
        if (count == 0)
                return 0;
 
-       LOG_DEBUG(VHOST_DATA,
-               "(%"PRIu64") res_start_idx %d| res_end_idx Index %d\n",
-               dev->device_fh, res_start_idx, res_end_idx);
+       LOG_DEBUG(VHOST_DATA, "(%d) start_idx %d | end_idx %d\n",
+               dev->vid, start_idx, start_idx + count);
 
        /* Retrieve all of the desc indexes first to avoid caching issues. */
-       rte_prefetch0(&vq->avail->ring[res_start_idx & (vq->size - 1)]);
+       rte_prefetch0(&vq->avail->ring[start_idx & (vq->size - 1)]);
        for (i = 0; i < count; i++) {
-               desc_indexes[i] = vq->avail->ring[(res_start_idx + i) &
-                                                 (vq->size - 1)];
+               used_idx = (start_idx + i) & (vq->size - 1);
+               desc_indexes[i] = vq->avail->ring[used_idx];
+               vq->used->ring[used_idx].id = desc_indexes[i];
+               vq->used->ring[used_idx].len = pkts[i]->pkt_len +
+                                              dev->vhost_hlen;
+               vhost_log_used_vring(dev, vq,
+                       offsetof(struct vring_used, ring[used_idx]),
+                       sizeof(vq->used->ring[used_idx]));
        }
 
        rte_prefetch0(&vq->desc[desc_indexes[0]]);
        for (i = 0; i < count; i++) {
                uint16_t desc_idx = desc_indexes[i];
-               uint16_t used_idx = (res_start_idx + i) & (vq->size - 1);
-               uint32_t copied;
                int err;
 
-               err = copy_mbuf_to_desc(dev, vq, pkts[i], desc_idx, &copied);
-
-               vq->used->ring[used_idx].id = desc_idx;
-               if (unlikely(err))
-                       vq->used->ring[used_idx].len = vq->vhost_hlen;
-               else
-                       vq->used->ring[used_idx].len = copied + vq->vhost_hlen;
-               vhost_log_used_vring(dev, vq,
-                       offsetof(struct vring_used, ring[used_idx]),
-                       sizeof(vq->used->ring[used_idx]));
+               err = copy_mbuf_to_desc(dev, vq, pkts[i], desc_idx);
+               if (unlikely(err)) {
+                       used_idx = (start_idx + i) & (vq->size - 1);
+                       vq->used->ring[used_idx].len = dev->vhost_hlen;
+                       vhost_log_used_vring(dev, vq,
+                               offsetof(struct vring_used, ring[used_idx]),
+                               sizeof(vq->used->ring[used_idx]));
+               }
 
                if (i + 1 < count)
                        rte_prefetch0(&vq->desc[desc_indexes[i+1]]);
@@ -315,12 +276,8 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 
        rte_smp_wmb();
 
-       /* Wait until it's our turn to add our buffer to the used ring. */
-       while (unlikely(vq->last_used_idx != res_start_idx))
-               rte_pause();
-
        *(volatile uint16_t *)&vq->used->idx += count;
-       vq->last_used_idx = res_end_idx;
+       vq->last_used_idx += count;
        vhost_log_used_vring(dev, vq,
                offsetof(struct vring_used, idx),
                sizeof(vq->used->idx));
@@ -337,7 +294,8 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 
 static inline int
 fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
-            uint32_t *allocated, uint32_t *vec_idx)
+            uint32_t *allocated, uint32_t *vec_idx,
+            struct buf_vector *buf_vec)
 {
        uint16_t idx = vq->avail->ring[avail_idx & (vq->size - 1)];
        uint32_t vec_id = *vec_idx;
@@ -348,9 +306,9 @@ fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
                        return -1;
 
                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) == 0)
@@ -366,39 +324,30 @@ fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
 }
 
 /*
- * As many data cores may want to access available buffers concurrently,
- * they need to be reserved.
- *
  * Returns -1 on fail, 0 on success
  */
 static inline int
 reserve_avail_buf_mergeable(struct vhost_virtqueue *vq, uint32_t size,
-                           uint16_t *start, uint16_t *end)
+                           uint16_t *end, struct buf_vector *buf_vec)
 {
-       uint16_t res_start_idx;
-       uint16_t res_cur_idx;
+       uint16_t cur_idx;
        uint16_t avail_idx;
-       uint32_t allocated;
-       uint32_t vec_idx;
-       uint16_t tries;
+       uint32_t allocated = 0;
+       uint32_t vec_idx = 0;
+       uint16_t tries = 0;
 
-again:
-       res_start_idx = vq->last_used_idx_res;
-       res_cur_idx  = res_start_idx;
+       cur_idx  = vq->last_used_idx;
 
-       allocated = 0;
-       vec_idx   = 0;
-       tries     = 0;
        while (1) {
                avail_idx = *((volatile uint16_t *)&vq->avail->idx);
-               if (unlikely(res_cur_idx == avail_idx))
+               if (unlikely(cur_idx == avail_idx))
                        return -1;
 
-               if (unlikely(fill_vec_buf(vq, res_cur_idx, &allocated,
-                                         &vec_idx) < 0))
+               if (unlikely(fill_vec_buf(vq, cur_idx, &allocated,
+                                         &vec_idx, buf_vec) < 0))
                        return -1;
 
-               res_cur_idx++;
+               cur_idx++;
                tries++;
 
                if (allocated >= size)
@@ -413,27 +362,19 @@ again:
                        return -1;
        }
 
-       /*
-        * update vq->last_used_idx_res atomically.
-        * retry again if failed.
-        */
-       if (rte_atomic16_cmpset(&vq->last_used_idx_res,
-                               res_start_idx, res_cur_idx) == 0)
-               goto again;
-
-       *start = res_start_idx;
-       *end   = res_cur_idx;
+       *end = cur_idx;
        return 0;
 }
 
 static inline uint32_t __attribute__((always_inline))
 copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
-                           uint16_t res_start_idx, uint16_t res_end_idx,
-                           struct rte_mbuf *m)
+                           uint16_t end_idx, struct rte_mbuf *m,
+                           struct buf_vector *buf_vec)
 {
        struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
        uint32_t vec_idx = 0;
-       uint16_t cur_idx = res_start_idx;
+       uint16_t start_idx = vq->last_used_idx;
+       uint16_t cur_idx = start_idx;
        uint64_t desc_addr;
        uint32_t mbuf_offset, mbuf_avail;
        uint32_t desc_offset, desc_avail;
@@ -443,34 +384,33 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
        if (unlikely(m == NULL))
                return 0;
 
-       LOG_DEBUG(VHOST_DATA,
-               "(%"PRIu64") Current Index %d| End Index %d\n",
-               dev->device_fh, cur_idx, res_end_idx);
+       LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
+               dev->vid, cur_idx, end_idx);
 
-       if (vq->buf_vec[vec_idx].buf_len < vq->vhost_hlen)
+       if (buf_vec[vec_idx].buf_len < dev->vhost_hlen)
                return -1;
 
-       desc_addr = gpa_to_vva(dev, vq->buf_vec[vec_idx].buf_addr);
+       desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
        rte_prefetch0((void *)(uintptr_t)desc_addr);
 
-       virtio_hdr.num_buffers = res_end_idx - res_start_idx;
-       LOG_DEBUG(VHOST_DATA, "(%"PRIu64") RX: Num merge buffers %d\n",
-               dev->device_fh, virtio_hdr.num_buffers);
+       virtio_hdr.num_buffers = end_idx - start_idx;
+       LOG_DEBUG(VHOST_DATA, "(%d) RX: num merge buffers %d\n",
+               dev->vid, virtio_hdr.num_buffers);
 
        virtio_enqueue_offload(m, &virtio_hdr.hdr);
-       copy_virtio_net_hdr(vq, desc_addr, virtio_hdr);
-       vhost_log_write(dev, vq->buf_vec[vec_idx].buf_addr, vq->vhost_hlen);
-       PRINT_PACKET(dev, (uintptr_t)desc_addr, vq->vhost_hlen, 0);
+       copy_virtio_net_hdr(dev, desc_addr, virtio_hdr);
+       vhost_log_write(dev, buf_vec[vec_idx].buf_addr, dev->vhost_hlen);
+       PRINT_PACKET(dev, (uintptr_t)desc_addr, dev->vhost_hlen, 0);
 
-       desc_avail  = vq->buf_vec[vec_idx].buf_len - vq->vhost_hlen;
-       desc_offset = vq->vhost_hlen;
+       desc_avail  = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
+       desc_offset = dev->vhost_hlen;
 
        mbuf_avail  = rte_pktmbuf_data_len(m);
        mbuf_offset = 0;
        while (mbuf_avail != 0 || m->next != NULL) {
                /* done with current desc buf, get the next one */
                if (desc_avail == 0) {
-                       desc_idx = vq->buf_vec[vec_idx].desc_idx;
+                       desc_idx = buf_vec[vec_idx].desc_idx;
 
                        if (!(vq->desc[desc_idx].flags & VRING_DESC_F_NEXT)) {
                                /* Update used ring with desc information */
@@ -484,12 +424,12 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        }
 
                        vec_idx++;
-                       desc_addr = gpa_to_vva(dev, vq->buf_vec[vec_idx].buf_addr);
+                       desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
 
                        /* Prefetch buffer address. */
                        rte_prefetch0((void *)(uintptr_t)desc_addr);
                        desc_offset = 0;
-                       desc_avail  = vq->buf_vec[vec_idx].buf_len;
+                       desc_avail  = buf_vec[vec_idx].buf_len;
                }
 
                /* done with current mbuf, get the next one */
@@ -504,7 +444,7 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
                rte_memcpy((void *)((uintptr_t)(desc_addr + desc_offset)),
                        rte_pktmbuf_mtod_offset(m, void *, mbuf_offset),
                        cpy_len);
-               vhost_log_write(dev, vq->buf_vec[vec_idx].buf_addr + desc_offset,
+               vhost_log_write(dev, buf_vec[vec_idx].buf_addr + desc_offset,
                        cpy_len);
                PRINT_PACKET(dev, (uintptr_t)(desc_addr + desc_offset),
                        cpy_len, 0);
@@ -516,13 +456,13 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
        }
 
        used_idx = cur_idx & (vq->size - 1);
-       vq->used->ring[used_idx].id = vq->buf_vec[vec_idx].desc_idx;
+       vq->used->ring[used_idx].id = buf_vec[vec_idx].desc_idx;
        vq->used->ring[used_idx].len = desc_offset;
        vhost_log_used_vring(dev, vq,
                offsetof(struct vring_used, ring[used_idx]),
                sizeof(vq->used->ring[used_idx]));
 
-       return res_end_idx - res_start_idx;
+       return end_idx - start_idx;
 }
 
 static inline uint32_t __attribute__((always_inline))
@@ -531,14 +471,13 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 {
        struct vhost_virtqueue *vq;
        uint32_t pkt_idx = 0, nr_used = 0;
-       uint16_t start, end;
+       uint16_t end;
+       struct buf_vector buf_vec[BUF_VECTOR_MAX];
 
-       LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_merge_rx()\n",
-               dev->device_fh);
+       LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
        if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->virt_qp_nb))) {
-               RTE_LOG(ERR, VHOST_DATA,
-                       "%s (%"PRIu64"): virtqueue idx:%d invalid.\n",
-                       __func__, dev->device_fh, queue_id);
+               RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
+                       dev->vid, __func__, queue_id);
                return 0;
        }
 
@@ -551,27 +490,20 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
                return 0;
 
        for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
-               uint32_t pkt_len = pkts[pkt_idx]->pkt_len + vq->vhost_hlen;
+               uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
 
                if (unlikely(reserve_avail_buf_mergeable(vq, pkt_len,
-                                                        &start, &end) < 0)) {
+                                                        &end, buf_vec) < 0)) {
                        LOG_DEBUG(VHOST_DATA,
-                               "(%" PRIu64 ") Failed to get enough desc from vring\n",
-                               dev->device_fh);
+                               "(%d) failed to get enough desc from vring\n",
+                               dev->vid);
                        break;
                }
 
-               nr_used = copy_mbuf_to_desc_mergeable(dev, vq, start, end,
-                                                     pkts[pkt_idx]);
+               nr_used = copy_mbuf_to_desc_mergeable(dev, vq, end,
+                                                     pkts[pkt_idx], buf_vec);
                rte_smp_wmb();
 
-               /*
-                * Wait until it's our turn to add our buffer
-                * to the used ring.
-                */
-               while (unlikely(vq->last_used_idx != start))
-                       rte_pause();
-
                *(volatile uint16_t *)&vq->used->idx += nr_used;
                vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
                        sizeof(vq->used->idx));
@@ -592,9 +524,14 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 }
 
 uint16_t
-rte_vhost_enqueue_burst(struct virtio_net *dev, uint16_t queue_id,
+rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
        struct rte_mbuf **pkts, uint16_t count)
 {
+       struct virtio_net *dev = get_device(vid);
+
+       if (!dev)
+               return 0;
+
        if (dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF))
                return virtio_dev_merge_rx(dev, queue_id, pkts, count);
        else
@@ -747,22 +684,53 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
        uint32_t nr_desc = 1;
 
        desc = &vq->desc[desc_idx];
-       if (unlikely(desc->len < vq->vhost_hlen))
+       if (unlikely(desc->len < dev->vhost_hlen))
                return -1;
 
        desc_addr = gpa_to_vva(dev, desc->addr);
-       rte_prefetch0((void *)(uintptr_t)desc_addr);
-
-       /* Retrieve virtio net header */
        hdr = (struct virtio_net_hdr *)((uintptr_t)desc_addr);
-       desc_avail  = desc->len - vq->vhost_hlen;
-       desc_offset = vq->vhost_hlen;
+       rte_prefetch0(hdr);
+
+       /*
+        * A virtio driver normally uses at least 2 desc buffers
+        * for Tx: the first for storing the header, and others
+        * for storing the data.
+        */
+       if (likely((desc->len == dev->vhost_hlen) &&
+                  (desc->flags & VRING_DESC_F_NEXT) != 0)) {
+               desc = &vq->desc[desc->next];
+
+               desc_addr = gpa_to_vva(dev, desc->addr);
+               rte_prefetch0((void *)(uintptr_t)desc_addr);
+
+               desc_offset = 0;
+               desc_avail  = desc->len;
+               nr_desc    += 1;
+
+               PRINT_PACKET(dev, (uintptr_t)desc_addr, desc->len, 0);
+       } else {
+               desc_avail  = desc->len - dev->vhost_hlen;
+               desc_offset = dev->vhost_hlen;
+       }
 
        mbuf_offset = 0;
        mbuf_avail  = m->buf_len - RTE_PKTMBUF_HEADROOM;
-       while (desc_avail != 0 || (desc->flags & VRING_DESC_F_NEXT) != 0) {
+       while (1) {
+               cpy_len = RTE_MIN(desc_avail, mbuf_avail);
+               rte_memcpy(rte_pktmbuf_mtod_offset(cur, void *, mbuf_offset),
+                       (void *)((uintptr_t)(desc_addr + desc_offset)),
+                       cpy_len);
+
+               mbuf_avail  -= cpy_len;
+               mbuf_offset += cpy_len;
+               desc_avail  -= cpy_len;
+               desc_offset += cpy_len;
+
                /* This desc reaches to its end, get the next one */
                if (desc_avail == 0) {
+                       if ((desc->flags & VRING_DESC_F_NEXT) == 0)
+                               break;
+
                        if (unlikely(desc->next >= vq->size ||
                                     ++nr_desc >= vq->size))
                                return -1;
@@ -798,16 +766,6 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        mbuf_offset = 0;
                        mbuf_avail  = cur->buf_len - RTE_PKTMBUF_HEADROOM;
                }
-
-               cpy_len = RTE_MIN(desc_avail, mbuf_avail);
-               rte_memcpy(rte_pktmbuf_mtod_offset(cur, void *, mbuf_offset),
-                       (void *)((uintptr_t)(desc_addr + desc_offset)),
-                       cpy_len);
-
-               mbuf_avail  -= cpy_len;
-               mbuf_offset += cpy_len;
-               desc_avail  -= cpy_len;
-               desc_offset += cpy_len;
        }
 
        prev->data_len = mbuf_offset;
@@ -820,9 +778,10 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 }
 
 uint16_t
-rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
+rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
        struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count)
 {
+       struct virtio_net *dev;
        struct rte_mbuf *rarp_mbuf = NULL;
        struct vhost_virtqueue *vq;
        uint32_t desc_indexes[MAX_PKT_BURST];
@@ -831,10 +790,13 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
        uint16_t free_entries;
        uint16_t avail_idx;
 
+       dev = get_device(vid);
+       if (!dev)
+               return 0;
+
        if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->virt_qp_nb))) {
-               RTE_LOG(ERR, VHOST_DATA,
-                       "%s (%"PRIu64"): virtqueue idx:%d invalid.\n",
-                       __func__, dev->device_fh, queue_id);
+               RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
+                       dev->vid, __func__, queue_id);
                return 0;
        }
 
@@ -870,35 +832,37 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
        if (free_entries == 0)
                goto out;
 
-       LOG_DEBUG(VHOST_DATA, "%s (%"PRIu64")\n", __func__, dev->device_fh);
+       LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
 
        /* Prefetch available ring to retrieve head indexes. */
        used_idx = vq->last_used_idx & (vq->size - 1);
        rte_prefetch0(&vq->avail->ring[used_idx]);
+       rte_prefetch0(&vq->used->ring[used_idx]);
 
        count = RTE_MIN(count, MAX_PKT_BURST);
        count = RTE_MIN(count, free_entries);
-       LOG_DEBUG(VHOST_DATA, "(%"PRIu64") about to dequeue %u buffers\n",
-                       dev->device_fh, count);
+       LOG_DEBUG(VHOST_DATA, "(%d) about to dequeue %u buffers\n",
+                       dev->vid, count);
 
        /* Retrieve all of the head indexes first to avoid caching issues. */
        for (i = 0; i < count; i++) {
-               desc_indexes[i] = vq->avail->ring[(vq->last_used_idx + i) &
-                                       (vq->size - 1)];
+               used_idx = (vq->last_used_idx + i) & (vq->size - 1);
+               desc_indexes[i] = vq->avail->ring[used_idx];
+
+               vq->used->ring[used_idx].id  = desc_indexes[i];
+               vq->used->ring[used_idx].len = 0;
+               vhost_log_used_vring(dev, vq,
+                               offsetof(struct vring_used, ring[used_idx]),
+                               sizeof(vq->used->ring[used_idx]));
        }
 
        /* Prefetch descriptor index. */
        rte_prefetch0(&vq->desc[desc_indexes[0]]);
-       rte_prefetch0(&vq->used->ring[vq->last_used_idx & (vq->size - 1)]);
-
        for (i = 0; i < count; i++) {
                int err;
 
-               if (likely(i + 1 < count)) {
+               if (likely(i + 1 < count))
                        rte_prefetch0(&vq->desc[desc_indexes[i + 1]]);
-                       rte_prefetch0(&vq->used->ring[(used_idx + 1) &
-                                                     (vq->size - 1)]);
-               }
 
                pkts[i] = rte_pktmbuf_alloc(mbuf_pool);
                if (unlikely(pkts[i] == NULL)) {
@@ -912,18 +876,12 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
                        rte_pktmbuf_free(pkts[i]);
                        break;
                }
-
-               used_idx = vq->last_used_idx++ & (vq->size - 1);
-               vq->used->ring[used_idx].id  = desc_indexes[i];
-               vq->used->ring[used_idx].len = 0;
-               vhost_log_used_vring(dev, vq,
-                               offsetof(struct vring_used, ring[used_idx]),
-                               sizeof(vq->used->ring[used_idx]));
        }
 
        rte_smp_wmb();
        rte_smp_rmb();
        vq->used->idx += i;
+       vq->last_used_idx += i;
        vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
                        sizeof(vq->used->idx));