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Date:   Fri, 24 May 2019 18:25:39 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Jiong Wang <jiong.wang@...ronome.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>, Netdev <netdev@...r.kernel.org>,
        oss-drivers@...ronome.com, David Miller <davem@...emloft.net>,
        paul.burton@...s.com, udknight@...il.com, zlim.lnx@...il.com,
        illusionist.neo@...il.com, naveen.n.rao@...ux.ibm.com,
        sandipan@...ux.ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: Re: [PATCH v8 bpf-next 15/16] riscv: bpf: eliminate zero extension code-gen

On Fri, 24 May 2019 at 13:36, Jiong Wang <jiong.wang@...ronome.com> wrote:
>
> Cc: Björn Töpel <bjorn.topel@...il.com>
> Acked-by: Björn Töpel <bjorn.topel@...il.com>
> Tested-by: Björn Töpel <bjorn.topel@...il.com>
> Signed-off-by: Jiong Wang <jiong.wang@...ronome.com>
> ---
>  arch/riscv/net/bpf_jit_comp.c | 43 ++++++++++++++++++++++++++++++-------------
>  1 file changed, 30 insertions(+), 13 deletions(-)
>
> diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
> index 80b12aa..c4c836e 100644
> --- a/arch/riscv/net/bpf_jit_comp.c
> +++ b/arch/riscv/net/bpf_jit_comp.c
> @@ -731,6 +731,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>  {
>         bool is64 = BPF_CLASS(insn->code) == BPF_ALU64 ||
>                     BPF_CLASS(insn->code) == BPF_JMP;
> +       struct bpf_prog_aux *aux = ctx->prog->aux;
>         int rvoff, i = insn - ctx->prog->insnsi;
>         u8 rd = -1, rs = -1, code = insn->code;
>         s16 off = insn->off;
> @@ -742,8 +743,13 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>         /* dst = src */
>         case BPF_ALU | BPF_MOV | BPF_X:
>         case BPF_ALU64 | BPF_MOV | BPF_X:
> +               if (imm == 1) {
> +                       /* Special mov32 for zext */
> +                       emit_zext_32(rd, ctx);
> +                       break;
> +               }

Hmm, missing is64 check here (fall-through for 64-bit movs)?

Björn

>                 emit(is64 ? rv_addi(rd, rs, 0) : rv_addiw(rd, rs, 0), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>
> @@ -771,19 +777,19 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>         case BPF_ALU | BPF_MUL | BPF_X:
>         case BPF_ALU64 | BPF_MUL | BPF_X:
>                 emit(is64 ? rv_mul(rd, rd, rs) : rv_mulw(rd, rd, rs), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_DIV | BPF_X:
>         case BPF_ALU64 | BPF_DIV | BPF_X:
>                 emit(is64 ? rv_divu(rd, rd, rs) : rv_divuw(rd, rd, rs), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_MOD | BPF_X:
>         case BPF_ALU64 | BPF_MOD | BPF_X:
>                 emit(is64 ? rv_remu(rd, rd, rs) : rv_remuw(rd, rd, rs), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_LSH | BPF_X:
> @@ -867,7 +873,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>         case BPF_ALU | BPF_MOV | BPF_K:
>         case BPF_ALU64 | BPF_MOV | BPF_K:
>                 emit_imm(rd, imm, ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>
> @@ -882,7 +888,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                         emit(is64 ? rv_add(rd, rd, RV_REG_T1) :
>                              rv_addw(rd, rd, RV_REG_T1), ctx);
>                 }
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_SUB | BPF_K:
> @@ -895,7 +901,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                         emit(is64 ? rv_sub(rd, rd, RV_REG_T1) :
>                              rv_subw(rd, rd, RV_REG_T1), ctx);
>                 }
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_AND | BPF_K:
> @@ -906,7 +912,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                         emit_imm(RV_REG_T1, imm, ctx);
>                         emit(rv_and(rd, rd, RV_REG_T1), ctx);
>                 }
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_OR | BPF_K:
> @@ -917,7 +923,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                         emit_imm(RV_REG_T1, imm, ctx);
>                         emit(rv_or(rd, rd, RV_REG_T1), ctx);
>                 }
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_XOR | BPF_K:
> @@ -928,7 +934,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                         emit_imm(RV_REG_T1, imm, ctx);
>                         emit(rv_xor(rd, rd, RV_REG_T1), ctx);
>                 }
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_MUL | BPF_K:
> @@ -936,7 +942,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                 emit_imm(RV_REG_T1, imm, ctx);
>                 emit(is64 ? rv_mul(rd, rd, RV_REG_T1) :
>                      rv_mulw(rd, rd, RV_REG_T1), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_DIV | BPF_K:
> @@ -944,7 +950,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                 emit_imm(RV_REG_T1, imm, ctx);
>                 emit(is64 ? rv_divu(rd, rd, RV_REG_T1) :
>                      rv_divuw(rd, rd, RV_REG_T1), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_MOD | BPF_K:
> @@ -952,7 +958,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                 emit_imm(RV_REG_T1, imm, ctx);
>                 emit(is64 ? rv_remu(rd, rd, RV_REG_T1) :
>                      rv_remuw(rd, rd, RV_REG_T1), ctx);
> -               if (!is64)
> +               if (!is64 && !aux->verifier_zext)
>                         emit_zext_32(rd, ctx);
>                 break;
>         case BPF_ALU | BPF_LSH | BPF_K:
> @@ -1239,6 +1245,8 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                 emit_imm(RV_REG_T1, off, ctx);
>                 emit(rv_add(RV_REG_T1, RV_REG_T1, rs), ctx);
>                 emit(rv_lbu(rd, 0, RV_REG_T1), ctx);
> +               if (insn_is_zext(&insn[1]))
> +                       return 1;
>                 break;
>         case BPF_LDX | BPF_MEM | BPF_H:
>                 if (is_12b_int(off)) {
> @@ -1249,6 +1257,8 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                 emit_imm(RV_REG_T1, off, ctx);
>                 emit(rv_add(RV_REG_T1, RV_REG_T1, rs), ctx);
>                 emit(rv_lhu(rd, 0, RV_REG_T1), ctx);
> +               if (insn_is_zext(&insn[1]))
> +                       return 1;
>                 break;
>         case BPF_LDX | BPF_MEM | BPF_W:
>                 if (is_12b_int(off)) {
> @@ -1259,6 +1269,8 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>                 emit_imm(RV_REG_T1, off, ctx);
>                 emit(rv_add(RV_REG_T1, RV_REG_T1, rs), ctx);
>                 emit(rv_lwu(rd, 0, RV_REG_T1), ctx);
> +               if (insn_is_zext(&insn[1]))
> +                       return 1;
>                 break;
>         case BPF_LDX | BPF_MEM | BPF_DW:
>                 if (is_12b_int(off)) {
> @@ -1503,6 +1515,11 @@ static void bpf_flush_icache(void *start, void *end)
>         flush_icache_range((unsigned long)start, (unsigned long)end);
>  }
>
> +bool bpf_jit_needs_zext(void)
> +{
> +       return true;
> +}
> +
>  struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>  {
>         bool tmp_blinded = false, extra_pass = false;
> --
> 2.7.4
>

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