On Thu, Oct 31, 2019 at 09:47:48AM +0100, Björn Töpel wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
>
> Inline the xsk_map_lookup_elem() via implementing the map_gen_lookup()
> callback. This results in emitting the bpf instructions in place of
> bpf_map_lookup_elem() helper call and better performance of bpf
> programs.
>
> Acked-by: Jonathan Lemon <jonathan.lemon@xxxxxxxxx>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
> ---
> kernel/bpf/xskmap.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
> index edcbd863650e..fa32f775b4de 100644
> --- a/kernel/bpf/xskmap.c
> +++ b/kernel/bpf/xskmap.c
> @@ -163,6 +163,22 @@ struct xdp_sock *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
> return xs;
> }
>
> +static u32 xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
> +{
> + const int ret = BPF_REG_0, mp = BPF_REG_1, index = BPF_REG_2;
> + struct bpf_insn *insn = insn_buf;
> +
> + *insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
> + *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
> + *insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(sizeof(struct xsk_sock *)));
> + *insn++ = BPF_ALU64_IMM(BPF_ADD, mp, offsetof(struct xsk_map, xsk_map));
> + *insn++ = BPF_ALU64_REG(BPF_ADD, ret, mp);
> + *insn++ = BPF_LDX_MEM(BPF_DW, ret, ret, 0);
Your map slots are always exactly sizeof(struct xdp_sock *), right? Wouldn't
this BPF_DW crash on 32 bit?
Meaning, it would have to be BPF_LDX_MEM(BPF_SIZEOF(struct xsk_sock *), ...)?
> + *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
> + *insn++ = BPF_MOV64_IMM(ret, 0);
> + return insn - insn_buf;
> +}
> +
> int __xsk_map_redirect(struct bpf_map *map, struct xdp_buff *xdp,
> struct xdp_sock *xs)
> {
> @@ -303,6 +319,7 @@ const struct bpf_map_ops xsk_map_ops = {
> .map_free = xsk_map_free,
> .map_get_next_key = xsk_map_get_next_key,
> .map_lookup_elem = xsk_map_lookup_elem,
> + .map_gen_lookup = xsk_map_gen_lookup,
> .map_lookup_elem_sys_only = xsk_map_lookup_elem_sys_only,
> .map_update_elem = xsk_map_update_elem,
> .map_delete_elem = xsk_map_delete_elem,
> --
> 2.20.1
>
