[PATCH 2/3] vhost: fix virtqueue access lock in datapath

[David Marchand]

Now that a r/w lock is used, the access_ok field should only be updated
under a write lock.

Since the datapath code only takes a read lock on the virtqueue to check
access_ok, this lock must be released and a write lock taken before
calling vring_translate().

Fixes: 03f77d66d966 ("vhost: change virtqueue access lock to a read/write one")
Cc: sta...@dpdk.org

Signed-off-by: David Marchand <david.march...@redhat.com>
---
 lib/vhost/virtio_net.c | 60 +++++++++++++++++++++++++++++++-----------
 1 file changed, 44 insertions(+), 16 deletions(-)

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 759a78e3e3..4116f79d4f 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -1694,6 +1694,17 @@ virtio_dev_rx_packed(struct virtio_net *dev,
        return pkt_idx;
 }
 
+static void
+virtio_dev_vring_translate(struct virtio_net *dev, struct vhost_virtqueue *vq)
+{
+       rte_rwlock_write_lock(&vq->access_lock);
+       vhost_user_iotlb_rd_lock(vq);
+       if (!vq->access_ok)
+               vring_translate(dev, vq);
+       vhost_user_iotlb_rd_unlock(vq);
+       rte_rwlock_write_unlock(&vq->access_lock);
+}
+
 static __rte_always_inline uint32_t
 virtio_dev_rx(struct virtio_net *dev, struct vhost_virtqueue *vq,
        struct rte_mbuf **pkts, uint32_t count)
@@ -1708,9 +1719,13 @@ virtio_dev_rx(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
 
        vhost_user_iotlb_rd_lock(vq);
 
-       if (unlikely(!vq->access_ok))
-               if (unlikely(vring_translate(dev, vq) < 0))
-                       goto out;
+       if (unlikely(!vq->access_ok)) {
+               vhost_user_iotlb_rd_unlock(vq);
+               rte_rwlock_read_unlock(&vq->access_lock);
+
+               virtio_dev_vring_translate(dev, vq);
+               goto out_no_unlock;
+       }
 
        count = RTE_MIN((uint32_t)MAX_PKT_BURST, count);
        if (count == 0)
@@ -1729,6 +1744,7 @@ virtio_dev_rx(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
 out_access_unlock:
        rte_rwlock_read_unlock(&vq->access_lock);
 
+out_no_unlock:
        return nb_tx;
 }
 
@@ -2523,9 +2539,13 @@ virtio_dev_rx_async_submit(struct virtio_net *dev, 
struct vhost_virtqueue *vq,
 
        vhost_user_iotlb_rd_lock(vq);
 
-       if (unlikely(!vq->access_ok))
-               if (unlikely(vring_translate(dev, vq) < 0))
-                       goto out;
+       if (unlikely(!vq->access_ok)) {
+               vhost_user_iotlb_rd_unlock(vq);
+               rte_rwlock_read_unlock(&vq->access_lock);
+
+               virtio_dev_vring_translate(dev, vq);
+               goto out_no_unlock;
+       }
 
        count = RTE_MIN((uint32_t)MAX_PKT_BURST, count);
        if (count == 0)
@@ -2546,6 +2566,7 @@ virtio_dev_rx_async_submit(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
 out_access_unlock:
        rte_rwlock_write_unlock(&vq->access_lock);
 
+out_no_unlock:
        return nb_tx;
 }
 
@@ -3576,11 +3597,13 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
 
        vhost_user_iotlb_rd_lock(vq);
 
-       if (unlikely(!vq->access_ok))
-               if (unlikely(vring_translate(dev, vq) < 0)) {
-                       count = 0;
-                       goto out;
-               }
+       if (unlikely(!vq->access_ok)) {
+               vhost_user_iotlb_rd_unlock(vq);
+               rte_rwlock_read_unlock(&vq->access_lock);
+
+               virtio_dev_vring_translate(dev, vq);
+               goto out_no_unlock;
+       }
 
        /*
         * Construct a RARP broadcast packet, and inject it to the "pkts"
@@ -3641,6 +3664,7 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
        if (unlikely(rarp_mbuf != NULL))
                count += 1;
 
+out_no_unlock:
        return count;
 }
 
@@ -4190,11 +4214,14 @@ rte_vhost_async_try_dequeue_burst(int vid, uint16_t 
queue_id,
 
        vhost_user_iotlb_rd_lock(vq);
 
-       if (unlikely(vq->access_ok == 0))
-               if (unlikely(vring_translate(dev, vq) < 0)) {
-                       count = 0;
-                       goto out;
-               }
+       if (unlikely(vq->access_ok == 0)) {
+               vhost_user_iotlb_rd_unlock(vq);
+               rte_rwlock_read_unlock(&vq->access_lock);
+
+               virtio_dev_vring_translate(dev, vq);
+               count = 0;
+               goto out_no_unlock;
+       }
 
        /*
         * Construct a RARP broadcast packet, and inject it to the "pkts"
@@ -4260,5 +4287,6 @@ rte_vhost_async_try_dequeue_burst(int vid, uint16_t 
queue_id,
        if (unlikely(rarp_mbuf != NULL))
                count += 1;
 
+out_no_unlock:
        return count;
 }
-- 
2.41.0