Re: [PATCH bpf-next] xsk: add multi-buffer support for sockets sharing umem

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Thu, Sep 07, 2023 at 09:20:32AM +0530, Tirthendu Sarkar wrote:
> Userspace applications indicate their multi-buffer capability to xsk
> using XSK_USE_SG socket bind flag. For sockets using shared umem the
> bind flag may contain XSK_USE_SG only for the first socket. For any
> subsequent socket the only option supported is XDP_SHARED_UMEM.
> 
> Add option XDP_UMEM_SG_FLAG in umem config flags to store the
> multi-buffer handling capability when indicated by XSK_USE_SG option in
> bing flag by the first socket. Use this to derive multi-buffer capability
> for subsequent sockets in xsk core.
> 
> Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@intel.com>
> Fixes: 81470b5c3c66 ("xsk: introduce XSK_USE_SG bind flag for xsk socket")

Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

> ---
>  include/net/xdp_sock.h  | 2 ++
>  net/xdp/xsk.c           | 2 +-
>  net/xdp/xsk_buff_pool.c | 3 +++
>  3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> index 1617af380162..69b472604b86 100644
> --- a/include/net/xdp_sock.h
> +++ b/include/net/xdp_sock.h
> @@ -14,6 +14,8 @@
>  #include <linux/mm.h>
>  #include <net/sock.h>
>  
> +#define XDP_UMEM_SG_FLAG (1 << 1)
> +
>  struct net_device;
>  struct xsk_queue;
>  struct xdp_buff;
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 55f8b9b0e06d..7482d0aca504 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -1228,7 +1228,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
>  
>  	xs->dev = dev;
>  	xs->zc = xs->umem->zc;
> -	xs->sg = !!(flags & XDP_USE_SG);
> +	xs->sg = !!(xs->umem->flags & XDP_UMEM_SG_FLAG);
>  	xs->queue_id = qid;
>  	xp_add_xsk(xs->pool, xs);
>  
> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> index b3f7b310811e..49cb9f9a09be 100644
> --- a/net/xdp/xsk_buff_pool.c
> +++ b/net/xdp/xsk_buff_pool.c
> @@ -170,6 +170,9 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
>  	if (err)
>  		return err;
>  
> +	if (flags & XDP_USE_SG)
> +		pool->umem->flags |= XDP_UMEM_SG_FLAG;
> +
>  	if (flags & XDP_USE_NEED_WAKEUP)
>  		pool->uses_need_wakeup = true;
>  	/* Tx needs to be explicitly woken up the first time.  Also
> -- 
> 2.34.1
>