linux-kernel - Re: [PATCH bpf-next 2/2] bpf,riscv: Implement bpf_addr_space

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Date: Sun, 24 Mar 2024 00:43:37 +0800
From: Pu Lehui <pulehui@...wei.com>
To: Puranjay Mohan <puranjay12@...il.com>
CC: Puranjay Mohan <puranjay12@...il.com>, Alexei Starovoitov
	<ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko
	<andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard
 Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, Yonghong Song
	<yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, KP
 Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo
	<haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Björn Töpel <bjorn@...nel.org>, Luke Nelson
	<luke.r.nels@...il.com>, Xi Wang <xi.wang@...il.com>, Paul Walmsley
	<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>, <bpf@...r.kernel.org>,
	<linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 2/2] bpf,riscv: Implement bpf_addr_space_cast
 instruction


On 2024/3/23 23:46, Puranjay Mohan wrote:
> LLVM generates bpf_addr_space_cast instruction while translating
[snip]
>   
>   /* Convert from ninsns to bytes. */
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index f51b832eafb6..3c389e75cb96 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -1083,6 +1083,16 @@ int bpf_jit_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 (BPF_CLASS(insn->code) == BPF_ALU64 && insn->off == BPF_ADDR_SPACE_CAST &&
> +		    insn->imm == 1U << 16) {
> +			emit_mv(RV_REG_T1, rs, ctx); > +			emit_zextw(RV_REG_T1, RV_REG_T1, ctx);
combine mv and zextw will be better
> +			emit_imm(rd, (ctx->user_vm_start >> 32) << 32, ctx);
> +			emit(rv_beq(RV_REG_T1, RV_REG_ZERO, 4), ctx);
> +			emit_or(RV_REG_T1, rd, RV_REG_T1, ctx);
> +			emit_mv(rd, RV_REG_T1, ctx);
ditto, but for or and mv