Re: [PATCH v2 1/5] vhost: fix virtqueue access check in datapath

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 12/5/23 10:45, David Marchand wrote:
> 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: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> Acked-by: Eelco Chaudron <echaudro@redhat.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin@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 8af20f1487..d00f4b03aa 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -1696,6 +1696,17 @@ 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)
> @@ -1710,9 +1721,13 @@ 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)
> @@ -1731,6 +1746,7 @@ 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;
>   }
>   
> @@ -2528,9 +2544,13 @@ 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)
> @@ -2551,6 +2571,7 @@ 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;
>   }
>   
> @@ -3581,11 +3602,13 @@ 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"
> @@ -3646,6 +3669,7 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
>   	if (unlikely(rarp_mbuf != NULL))
>   		count += 1;
>   
> +out_no_unlock:
>   	return count;
>   }
>   
> @@ -4196,11 +4220,14 @@ 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"
> @@ -4266,5 +4293,6 @@ rte_vhost_async_try_dequeue_burst(int vid, uint16_t queue_id,
>   	if (unlikely(rarp_mbuf != NULL))
>   		count += 1;
>   
> +out_no_unlock:
>   	return count;
>   }

Series applied to next-virtio/for-next-net

Thanks,
Maxime