Re: [PATCH 07/11] libbpf: add flags to umem config

["Björn Töpel" <bjorn.topel@gmail.com>]

On Thu, 20 Jun 2019 at 19:26, Kevin Laatz <kevin.laatz@intel.com> wrote:
>
> This patch adds a 'flags' field to the umem_config and umem_reg structs.
> This will allow for more options to be added for configuring umems.
>
> The first use for the flags field is to add a flag for unaligned chunks
> mode. These flags can either be user-provided or filled with a default.
>
> Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
> Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
> ---
>  tools/include/uapi/linux/if_xdp.h | 4 ++++
>  tools/lib/bpf/xsk.c               | 7 +++++++
>  tools/lib/bpf/xsk.h               | 2 ++
>  3 files changed, 13 insertions(+)
>
> diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h
> index caed8b1614ff..8548f2110a77 100644
> --- a/tools/include/uapi/linux/if_xdp.h
> +++ b/tools/include/uapi/linux/if_xdp.h
> @@ -17,6 +17,9 @@
>  #define XDP_COPY       (1 << 1) /* Force copy-mode */
>  #define XDP_ZEROCOPY   (1 << 2) /* Force zero-copy mode */
>
> +/* Flags for xsk_umem_config flags */
> +#define XDP_UMEM_UNALIGNED_CHUNKS (1 << 0)
> +
>  struct sockaddr_xdp {
>         __u16 sxdp_family;
>         __u16 sxdp_flags;
> @@ -52,6 +55,7 @@ struct xdp_umem_reg {
>         __u64 len; /* Length of packet data area */
>         __u32 chunk_size;
>         __u32 headroom;
> +       __u32 flags;
>  };
>
>  struct xdp_statistics {
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index 7ef6293b4fd7..df4207d4ff4a 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -115,6 +115,7 @@ static void xsk_set_umem_config(struct xsk_umem_config *cfg,
>                 cfg->comp_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
>                 cfg->frame_size = XSK_UMEM__DEFAULT_FRAME_SIZE;
>                 cfg->frame_headroom = XSK_UMEM__DEFAULT_FRAME_HEADROOM;
> +               cfg->flags = XSK_UMEM__DEFAULT_FLAGS;
>                 return;
>         }
>
> @@ -122,6 +123,7 @@ static void xsk_set_umem_config(struct xsk_umem_config *cfg,
>         cfg->comp_size = usr_cfg->comp_size;
>         cfg->frame_size = usr_cfg->frame_size;
>         cfg->frame_headroom = usr_cfg->frame_headroom;
> +       cfg->flags = usr_cfg->flags;
>  }
>
>  static int xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
> @@ -181,6 +183,11 @@ int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
>         mr.len = size;
>         mr.chunk_size = umem->config.frame_size;
>         mr.headroom = umem->config.frame_headroom;
> +       mr.flags = umem->config.flags;
> +
> +       /* Headroom must be 0 for unaligned chunks */
> +       if ((mr.flags & XDP_UMEM_UNALIGNED_CHUNKS) && mr.headroom != 0)
> +               return -EINVAL;

Ah. :-) I'd prefer that this is done in the bind syscall.

>
>         err = setsockopt(umem->fd, SOL_XDP, XDP_UMEM_REG, &mr, sizeof(mr));
>         if (err) {
> diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> index 82ea71a0f3ec..8d393873b70f 100644
> --- a/tools/lib/bpf/xsk.h
> +++ b/tools/lib/bpf/xsk.h
> @@ -170,12 +170,14 @@ LIBBPF_API int xsk_socket__fd(const struct xsk_socket *xsk);
>  #define XSK_UMEM__DEFAULT_FRAME_SHIFT    11 /* 2048 bytes */
>  #define XSK_UMEM__DEFAULT_FRAME_SIZE     (1 << XSK_UMEM__DEFAULT_FRAME_SHIFT)
>  #define XSK_UMEM__DEFAULT_FRAME_HEADROOM 0
> +#define XSK_UMEM__DEFAULT_FLAGS 0
>
>  struct xsk_umem_config {
>         __u32 fill_size;
>         __u32 comp_size;
>         __u32 frame_size;
>         __u32 frame_headroom;
> +       __u32 flags;
>  };
>
>  /* Flags for the libbpf_flags field. */
> --
> 2.17.1
>