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

[Simon Horman <horms@kernel.org>]

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")
> ---
>  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)

nit: This could be BIT(1)