netdev - Re: [PATCH bpf-next v4 11/14] xsk: add shared umem support between devices

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Date:   Tue, 28 Jul 2020 09:15:42 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Magnus Karlsson <magnus.karlsson@...el.com>, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        jonathan.lemon@...il.com, maximmi@...lanox.com
Cc:     bpf@...r.kernel.org, jeffrey.t.kirsher@...el.com,
        anthony.l.nguyen@...el.com, maciej.fijalkowski@...el.com,
        maciejromanfijalkowski@...il.com, cristian.dumitrescu@...el.com
Subject: Re: [PATCH bpf-next v4 11/14] xsk: add shared umem support between
 devices



On 2020-07-21 07:04, Magnus Karlsson wrote:
> Add support to share a umem between different devices. This mode
> can be invoked with the XDP_SHARED_UMEM bind flag. Previously,
> sharing was only supported within the same device. Note that when
> sharing a umem between devices, just as in the case of sharing a
> umem between queue ids, you need to create a fill ring and a
> completion ring and tie them to the socket (with two setsockopts,
> one for each ring) before you do the bind with the
> XDP_SHARED_UMEM flag. This so that the single-producer
> single-consumer semantics of the rings can be upheld.
> 
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>

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


> ---
>   net/xdp/xsk.c | 11 ++++-------
>   1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index e897755..ec2a2df 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -701,14 +701,11 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
>   			sockfd_put(sock);
>   			goto out_unlock;
>   		}
> -		if (umem_xs->dev != dev) {
> -			err = -EINVAL;
> -			sockfd_put(sock);
> -			goto out_unlock;
> -		}
>   
> -		if (umem_xs->queue_id != qid) {
> -			/* Share the umem with another socket on another qid */
> +		if (umem_xs->queue_id != qid || umem_xs->dev != dev) {
> +			/* Share the umem with another socket on another qid
> +			 * and/or device.
> +			 */
>   			xs->pool = xp_create_and_assign_umem(xs,
>   							     umem_xs->umem);
>   			if (!xs->pool) {
>