vhost: simplify mergeable Rx vring reservation

Let it return "num_buffers" we reserved, so that we could re-use it
with copy_mbuf_to_desc_mergeable() directly, instead of calculating
it again there.

Meanwhile, the return type of copy_mbuf_to_desc_mergeable is changed
to "int". -1 will be return on error.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Reviewed-by: Jianbo Liu <jianbo.liu@linaro.org>
Tested-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 27ebf3d..e449388 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -336,7 +336,7 @@ fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
  */
 static inline int
 reserve_avail_buf_mergeable(struct vhost_virtqueue *vq, uint32_t size,
-                           uint16_t *end, struct buf_vector *buf_vec)
+                           struct buf_vector *buf_vec, uint16_t *num_buffers)
 {
        uint16_t cur_idx;
        uint16_t avail_idx;
@@ -370,19 +370,18 @@ reserve_avail_buf_mergeable(struct vhost_virtqueue *vq, uint32_t size,
                        return -1;
        }
 
-       *end = cur_idx;
+       *num_buffers = cur_idx - vq->last_used_idx;
        return 0;
 }
 
-static inline uint32_t __attribute__((always_inline))
+static inline int __attribute__((always_inline))
 copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
-                           uint16_t end_idx, struct rte_mbuf *m,
-                           struct buf_vector *buf_vec)
+                           struct rte_mbuf *m, struct buf_vector *buf_vec,
+                           uint16_t num_buffers)
 {
        struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
        uint32_t vec_idx = 0;
-       uint16_t start_idx = vq->last_used_idx;
-       uint16_t cur_idx = start_idx;
+       uint16_t cur_idx = vq->last_used_idx;
        uint64_t desc_addr;
        uint32_t desc_chain_head;
        uint32_t desc_chain_len;
@@ -394,21 +393,21 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
        struct rte_mbuf *hdr_mbuf;
 
        if (unlikely(m == NULL))
-               return 0;
+               return -1;
 
        LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
-               dev->vid, cur_idx, end_idx);
+               dev->vid, cur_idx, cur_idx + num_buffers);
 
        desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
        if (buf_vec[vec_idx].buf_len < dev->vhost_hlen || !desc_addr)
-               return 0;
+               return -1;
 
        hdr_mbuf = m;
        hdr_addr = desc_addr;
        hdr_phys_addr = buf_vec[vec_idx].buf_addr;
        rte_prefetch0((void *)(uintptr_t)hdr_addr);
 
-       virtio_hdr.num_buffers = end_idx - start_idx;
+       virtio_hdr.num_buffers = num_buffers;
        LOG_DEBUG(VHOST_DATA, "(%d) RX: num merge buffers %d\n",
                dev->vid, virtio_hdr.num_buffers);
 
@@ -440,7 +439,7 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
                        desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
                        if (unlikely(!desc_addr))
-                               return 0;
+                               return -1;
 
                        /* Prefetch buffer address. */
                        rte_prefetch0((void *)(uintptr_t)desc_addr);
@@ -489,7 +488,7 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
                offsetof(struct vring_used, ring[used_idx]),
                sizeof(vq->used->ring[used_idx]));
 
-       return end_idx - start_idx;
+       return 0;
 }
 
 static inline uint32_t __attribute__((always_inline))
@@ -497,8 +496,8 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
        struct rte_mbuf **pkts, uint32_t count)
 {
        struct vhost_virtqueue *vq;
-       uint32_t pkt_idx = 0, nr_used = 0;
-       uint16_t end;
+       uint32_t pkt_idx = 0;
+       uint16_t num_buffers;
        struct buf_vector buf_vec[BUF_VECTOR_MAX];
 
        LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
@@ -519,22 +518,24 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
        for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
                uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
 
-               if (unlikely(reserve_avail_buf_mergeable(vq, pkt_len,
-                                                        &end, buf_vec) < 0)) {
+               if (unlikely(reserve_avail_buf_mergeable(vq, pkt_len, buf_vec,
+                                                        &num_buffers) < 0)) {
                        LOG_DEBUG(VHOST_DATA,
                                "(%d) failed to get enough desc from vring\n",
                                dev->vid);
                        break;
                }
 
-               nr_used = copy_mbuf_to_desc_mergeable(dev, vq, end,
-                                                     pkts[pkt_idx], buf_vec);
+               if (copy_mbuf_to_desc_mergeable(dev, vq, pkts[pkt_idx],
+                                               buf_vec, num_buffers) < 0)
+                       break;
+
                rte_smp_wmb();
 
-               *(volatile uint16_t *)&vq->used->idx += nr_used;
+               *(volatile uint16_t *)&vq->used->idx += num_buffers;
                vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
                        sizeof(vq->used->idx));
-               vq->last_used_idx += nr_used;
+               vq->last_used_idx += num_buffers;
        }
 
        if (likely(pkt_idx)) {