Re: [PATCH bpf-next v4 10/14] xsk: add shared umem support between queue ids

[Björn Töpel <bjorn.topel@xxxxxxxxx>]

On 2020-07-21 07:04, Magnus Karlsson wrote:
> Add support to share a umem between queue ids on the same
> device. This mode can be invoked with the XDP_SHARED_UMEM bind
> flag. Previously, sharing was only supported within the same
> queue id and device, and you shared one set of fill and
> completion rings. However, note that when sharing a umem between
> queue ids, you need to create a fill ring and a completion ring
> and tie them to the socket before you do the bind with the
> XDP_SHARED_UMEM flag. This so that the single-producer
> single-consumer semantics can be upheld.
>
> Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>

Acked-by: Björn Töpel <bjorn.topel@xxxxxxxxx>


> ---
>   include/net/xsk_buff_pool.h |  2 ++
>   net/xdp/xsk.c               | 44 ++++++++++++++++++++++++++++++--------------
>   net/xdp/xsk_buff_pool.c     | 26 ++++++++++++++++++++++++--
>   3 files changed, 56 insertions(+), 16 deletions(-)
>
> diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> index b4d6307..4d699dd 100644
> --- a/include/net/xsk_buff_pool.h
> +++ b/include/net/xsk_buff_pool.h
> @@ -75,6 +75,8 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
>   						struct xdp_umem *umem);
>   int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *dev,
>   		  u16 queue_id, u16 flags);
> +int xp_assign_dev_shared(struct xsk_buff_pool *pool, struct xdp_umem *umem,
> +			 struct net_device *dev, u16 queue_id);
>   void xp_destroy(struct xsk_buff_pool *pool);
>   void xp_release(struct xdp_buff_xsk *xskb);
>   void xp_get_pool(struct xsk_buff_pool *pool);
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index d0ff5e8..e897755 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -689,12 +689,6 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
>   			goto out_unlock;
>   		}
>   
> -		if (xs->fq_tmp || xs->cq_tmp) {
> -			/* Do not allow setting your own fq or cq. */
> -			err = -EINVAL;
> -			goto out_unlock;
> -		}
> -
>   		sock = xsk_lookup_xsk_from_fd(sxdp->sxdp_shared_umem_fd);
>   		if (IS_ERR(sock)) {
>   			err = PTR_ERR(sock);
> @@ -707,15 +701,41 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
>   			sockfd_put(sock);
>   			goto out_unlock;
>   		}
> -		if (umem_xs->dev != dev || umem_xs->queue_id != qid) {
> +		if (umem_xs->dev != dev) {
>   			err = -EINVAL;
>   			sockfd_put(sock);
>   			goto out_unlock;
>   		}
>   
> -		/* Share the buffer pool with the other socket. */
> -		xp_get_pool(umem_xs->pool);
> -		xs->pool = umem_xs->pool;
> +		if (umem_xs->queue_id != qid) {
> +			/* Share the umem with another socket on another qid */
> +			xs->pool = xp_create_and_assign_umem(xs,
> +							     umem_xs->umem);
> +			if (!xs->pool) {
> +				sockfd_put(sock);
> +				goto out_unlock;
> +			}
> +
> +			err = xp_assign_dev_shared(xs->pool, umem_xs->umem,
> +						   dev, qid);
> +			if (err) {
> +				xp_destroy(xs->pool);
> +				sockfd_put(sock);
> +				goto out_unlock;
> +			}
> +		} else {
> +			/* Share the buffer pool with the other socket. */
> +			if (xs->fq_tmp || xs->cq_tmp) {
> +				/* Do not allow setting your own fq or cq. */
> +				err = -EINVAL;
> +				sockfd_put(sock);
> +				goto out_unlock;
> +			}
> +
> +			xp_get_pool(umem_xs->pool);
> +			xs->pool = umem_xs->pool;
> +		}
> +
>   		xdp_get_umem(umem_xs->umem);
>   		WRITE_ONCE(xs->umem, umem_xs->umem);
>   		sockfd_put(sock);
> @@ -847,10 +867,6 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
>   			mutex_unlock(&xs->mutex);
>   			return -EBUSY;
>   		}
> -		if (!xs->umem) {
> -			mutex_unlock(&xs->mutex);
> -			return -EINVAL;
> -		}
>   
>   		q = (optname == XDP_UMEM_FILL_RING) ? &xs->fq_tmp :
>   			&xs->cq_tmp;
> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> index ca74a3e..688dc36 100644
> --- a/net/xdp/xsk_buff_pool.c
> +++ b/net/xdp/xsk_buff_pool.c
> @@ -123,8 +123,8 @@ static void xp_disable_drv_zc(struct xsk_buff_pool *pool)
>   	}
>   }
>   
> -int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *netdev,
> -		  u16 queue_id, u16 flags)
> +static int __xp_assign_dev(struct xsk_buff_pool *pool,
> +			   struct net_device *netdev, u16 queue_id, u16 flags)
>   {
>   	bool force_zc, force_copy;
>   	struct netdev_bpf bpf;
> @@ -193,6 +193,28 @@ int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *netdev,
>   	return err;
>   }
>   
> +int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *dev,
> +		  u16 queue_id, u16 flags)
> +{
> +	return __xp_assign_dev(pool, dev, queue_id, flags);
> +}
> +
> +int xp_assign_dev_shared(struct xsk_buff_pool *pool, struct xdp_umem *umem,
> +			 struct net_device *dev, u16 queue_id)
> +{
> +	u16 flags;
> +
> +	/* One fill and completion ring required for each queue id. */
> +	if (!pool->fq || !pool->cq)
> +		return -EINVAL;
> +
> +	flags = umem->zc ? XDP_ZEROCOPY : XDP_COPY;
> +	if (pool->uses_need_wakeup)
> +		flags |= XDP_USE_NEED_WAKEUP;
> +
> +	return __xp_assign_dev(pool, dev, queue_id, flags);
> +}
> +
>   void xp_clear_dev(struct xsk_buff_pool *pool)
>   {
>   	if (!pool->netdev)