On Mon, Apr 1, 2024 at 10:02 PM John Fastabend <john.fastabend@xxxxxxxxx> wrote:
>
> Andrii Nakryiko wrote:
> > Using new per-CPU BPF instruction implement inlining for per-CPU ARRAY
> > map lookup helper, if BPF JIT support is present.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > ---
> > kernel/bpf/arraymap.c | 33 +++++++++++++++++++++++++++++++++
> > 1 file changed, 33 insertions(+)
> >
> > diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> > index 13358675ff2e..8c1e6d7654bb 100644
> > --- a/kernel/bpf/arraymap.c
> > +++ b/kernel/bpf/arraymap.c
> > @@ -246,6 +246,38 @@ static void *percpu_array_map_lookup_elem(struct bpf_map *map, void *key)
> > return this_cpu_ptr(array->pptrs[index & array->index_mask]);
> > }
> >
> > +/* emit BPF instructions equivalent to C code of percpu_array_map_lookup_elem() */
> > +static int percpu_array_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
> > +{
> > + struct bpf_array *array = container_of(map, struct bpf_array, map);
> > + struct bpf_insn *insn = insn_buf;
>
> Nit, If you wanted to be consistent with array_*_map_gen_lookup,
>
I didn't in this case, I found these "aliases" more confusing than helpful.
> const int ret = BPF_REG_0;
> const int map_ptr = BPF_REG_1;
> const int index = BPF_REG_2;
>
> But, I think its easier to read as is.
>
Yep, that's what I thought as well.
> > +
> > + if (!bpf_jit_supports_percpu_insn())
> > + return -EOPNOTSUPP;
> > +
> > + if (map->map_flags & BPF_F_INNER_MAP)
> > + return -EOPNOTSUPP;
> > +
> > + BUILD_BUG_ON(offsetof(struct bpf_array, map) != 0);
> > + *insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, offsetof(struct bpf_array, pptrs));
> > +
> > + *insn++ = BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0);
> > + if (!map->bypass_spec_v1) {
> > + *insn++ = BPF_JMP_IMM(BPF_JGE, BPF_REG_0, map->max_entries, 6);
> > + *insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_0, array->index_mask);
> > + } else {
> > + *insn++ = BPF_JMP_IMM(BPF_JGE, BPF_REG_0, map->max_entries, 5);
> > + }
> > +
> > + *insn++ = BPF_ALU64_IMM(BPF_LSH, BPF_REG_0, 3);
> > + *insn++ = BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1);
> > + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0);
> > + *insn++ = BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0);
> > + *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
> > + *insn++ = BPF_MOV64_IMM(BPF_REG_0, 0);
> > + return insn - insn_buf;
> > +}
> > +
> > static void *percpu_array_map_lookup_percpu_elem(struct bpf_map *map, void *key, u32 cpu)
> > {
> > struct bpf_array *array = container_of(map, struct bpf_array, map);
> > @@ -776,6 +808,7 @@ const struct bpf_map_ops percpu_array_map_ops = {
> > .map_free = array_map_free,
> > .map_get_next_key = array_map_get_next_key,
> > .map_lookup_elem = percpu_array_map_lookup_elem,
> > + .map_gen_lookup = percpu_array_map_gen_lookup,
> > .map_update_elem = array_map_update_elem,
> > .map_delete_elem = array_map_delete_elem,
> > .map_lookup_percpu_elem = percpu_array_map_lookup_percpu_elem,
>
> Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
