linux-kernel - Re: [PATCH bpf-next] Enable zext optimization for more RV64G ALU ops

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Message-ID: <8736jk4ywp.fsf@netronome.com>
Date:   Fri, 05 Jul 2019 10:24:22 +0100
From:   Jiong Wang <jiong.wang@...ronome.com>
To:     Luke Nelson <lukenels@...washington.edu>
Cc:     linux-kernel@...r.kernel.org, Luke Nelson <luke.r.nels@...il.com>,
        Song Liu <liu.song.a23@...il.com>,
        Jiong Wang <jiong.wang@...ronome.com>,
        Xi Wang <xi.wang@...il.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        netdev@...r.kernel.org, linux-riscv@...ts.infradead.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] Enable zext optimization for more RV64G ALU ops


Luke Nelson writes:

> commit 66d0d5a854a6 ("riscv: bpf: eliminate zero extension code-gen")
> added the new zero-extension optimization for some BPF ALU operations.
>
> Since then, bugs in the JIT that have been fixed in the bpf tree require
> this optimization to be added to other operations: commit 1e692f09e091
> ("bpf, riscv: clear high 32 bits for ALU32 add/sub/neg/lsh/rsh/arsh"),
> and commit fe121ee531d1 ("bpf, riscv: clear target register high 32-bits
> for and/or/xor on ALU32")
>
> Now that these have been merged to bpf-next, the zext optimization can
> be enabled for the fixed operations.

LGTM, thanks.

Acked-by: Jiong Wang <jiong.wang@...ronome.com>

>
> Cc: Song Liu <liu.song.a23@...il.com>
> Cc: Jiong Wang <jiong.wang@...ronome.com>
> Cc: Xi Wang <xi.wang@...il.com>
> Signed-off-by: Luke Nelson <luke.r.nels@...il.com>
> ---
>  arch/riscv/net/bpf_jit_comp.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
> index 876cb9c705ce..5451ef3845f2 100644
> --- a/arch/riscv/net/bpf_jit_comp.c
> +++ b/arch/riscv/net/bpf_jit_comp.c
> @@ -757,31 +757,31 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>  	case BPF_ALU | BPF_ADD | BPF_X:
>  	case BPF_ALU64 | BPF_ADD | BPF_X:
>  		emit(is64 ? rv_add(rd, rd, rs) : rv_addw(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  	case BPF_ALU | BPF_SUB | BPF_X:
>  	case BPF_ALU64 | BPF_SUB | BPF_X:
>  		emit(is64 ? rv_sub(rd, rd, rs) : rv_subw(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  	case BPF_ALU | BPF_AND | BPF_X:
>  	case BPF_ALU64 | BPF_AND | BPF_X:
>  		emit(rv_and(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  	case BPF_ALU | BPF_OR | BPF_X:
>  	case BPF_ALU64 | BPF_OR | BPF_X:
>  		emit(rv_or(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  	case BPF_ALU | BPF_XOR | BPF_X:
>  	case BPF_ALU64 | BPF_XOR | BPF_X:
>  		emit(rv_xor(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  	case BPF_ALU | BPF_MUL | BPF_X:
> @@ -811,13 +811,13 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>  	case BPF_ALU | BPF_RSH | BPF_X:
>  	case BPF_ALU64 | BPF_RSH | BPF_X:
>  		emit(is64 ? rv_srl(rd, rd, rs) : rv_srlw(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  	case BPF_ALU | BPF_ARSH | BPF_X:
>  	case BPF_ALU64 | BPF_ARSH | BPF_X:
>  		emit(is64 ? rv_sra(rd, rd, rs) : rv_sraw(rd, rd, rs), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;
>  
> @@ -826,7 +826,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>  	case BPF_ALU64 | BPF_NEG:
>  		emit(is64 ? rv_sub(rd, RV_REG_ZERO, rd) :
>  		     rv_subw(rd, RV_REG_ZERO, rd), ctx);
> -		if (!is64)
> +		if (!is64 && !aux->verifier_zext)
>  			emit_zext_32(rd, ctx);
>  		break;