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From: Morten Brørup <mb@smartsharesystems.com>
To: "Konstantin Ananyev" <konstantin.ananyev@intel.com>, <dev@dpdk.org>
Cc: <jerinj@marvell.com>, <stephen@networkplumber.org>
Subject: Re: [dpdk-dev] [PATCH v2 5/5] bpf: x86 JIT support for packet data load instructions
Date: Thu, 28 May 2020 10:50:05 +0200
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35C61012@smartserver.smartshare.dk> (raw)
In-Reply-To: <20200527141653.15576-6-konstantin.ananyev@intel.com>

> From: Konstantin Ananyev [mailto:konstantin.ananyev@intel.com]
> Sent: Wednesday, May 27, 2020 4:17 PM
> 
> Make x86 JIT to generate native code for
> (BPF_ABS | <size> | BPF_LD) and (BPF_IND | <size> | BPF_LD)
> instructions.
> 
> Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> ---

[...]

> +/*
> + * helper function, used by emit_ld_mbuf().
> + * generates code for 'fast_path':
> + * calculate load offset and check is it inside first packet segment.
> + */
> +static void
> +emit_ldmb_fast_path(struct bpf_jit_state *st, const uint32_t
> rg[EBPF_REG_7],
> +	uint32_t sreg, uint32_t mode, uint32_t sz, uint32_t imm,
> +	const int32_t ofs[LDMB_OFS_NUM])
> +{
> +	/* make R2 contain *off* value */
> +
> +	if (sreg != rg[EBPF_REG_2]) {
> +		emit_mov_imm(st, EBPF_ALU64 | EBPF_MOV | BPF_K,
> +			rg[EBPF_REG_2], imm);
> +		if (mode == BPF_IND)
> +			emit_alu_reg(st, EBPF_ALU64 | BPF_ADD | BPF_X,
> +				sreg, rg[EBPF_REG_2]);
> +	} else
> +		/* BPF_IND with sreg == R2 */
> +		emit_alu_imm(st, EBPF_ALU64 | BPF_ADD | BPF_K,
> +			rg[EBPF_REG_2], imm);
> +
> +	/* R3 = mbuf->data_len */
> +	emit_ld_reg(st, BPF_LDX | BPF_MEM | BPF_H,
> +		rg[EBPF_REG_6], rg[EBPF_REG_3],
> +		offsetof(struct rte_mbuf, data_len));
> +
> +	/* R3 = R3 - R2 */
> +	emit_alu_reg(st, EBPF_ALU64 | BPF_SUB | BPF_X,
> +		rg[EBPF_REG_2], rg[EBPF_REG_3]);
> +
> +	/* JSLT R3, <sz> <slow_path> */
> +	emit_cmp_imm(st, EBPF_ALU64, rg[EBPF_REG_3], sz);
> +	emit_abs_jcc(st, BPF_JMP | EBPF_JSLT | BPF_K, ofs[LDMB_SLP_OFS]);
> +

[...]

> +
> +/*
> + * emit code for BPF_ABS/BPF_IND load.
> + * generates the following construction:
> + * fast_path:
> + *   off = ins->sreg + ins->imm
> + *   if (mbuf->data_len - off < ins->opsz)
> + *      goto slow_path;
> + *   ptr = mbuf->buf_addr + mbuf->data_off + off;
> + *   goto fin_part;
> + * slow_path:
> + *   typeof(ins->opsz) buf; //allocate space on the stack
> + *   ptr = __rte_pktmbuf_read(mbuf, off, ins->opsz, &buf);
> + *   if (ptr == NULL)
> + *      goto exit_label;
> + * fin_part:
> + *   res = *(typeof(ins->opsz))ptr;
> + *   res = bswap(res);
> + */

[...] 

The comparison for jumping to the slow path looks correct now.

I haven't reviewed it all in depth, but it certainly deserves an:

Acked-by: Morten Brørup <mb@smartsharesystems.com>


  reply	other threads:[~2020-05-28  8:50 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-18 15:52 [dpdk-dev] [PATCH 0/5] bpf: add support for BPF_ABS/BPF_IND instructions Konstantin Ananyev
2020-05-18 15:52 ` [dpdk-dev] [PATCH 1/5] test/bpf: fix few small issues Konstantin Ananyev
2020-06-24 21:33   ` [dpdk-dev] [dpdk-stable] " Thomas Monjalon
2020-05-18 15:52 ` [dpdk-dev] [PATCH 2/5] bpf: fix add/sub min/max estimations Konstantin Ananyev
2020-05-18 15:52 ` [dpdk-dev] [PATCH 3/5] bpf: add support for packet data load instructions Konstantin Ananyev
2020-05-18 15:52 ` [dpdk-dev] [PATCH 4/5] test/bpf: add new test cases for mbuf " Konstantin Ananyev
2020-05-18 15:52 ` [dpdk-dev] [PATCH 5/5] bpf: x86 JIT support for packet data " Konstantin Ananyev
2020-05-24 13:37   ` [dpdk-dev] [PATCH 5/5] bpf: x86 JIT support for packet data loadinstructions Morten Brørup
2020-05-24 23:08     ` Ananyev, Konstantin
2020-05-27 14:16 ` [dpdk-dev] [PATCH v2 0/5] bpf: add support for BPF_ABS/BPF_IND instructions Konstantin Ananyev
2020-05-27 14:16   ` [dpdk-dev] [PATCH v2 1/5] test/bpf: fix few small issues Konstantin Ananyev
2020-05-27 14:16   ` [dpdk-dev] [PATCH v2 2/5] bpf: fix add/sub min/max estimations Konstantin Ananyev
2020-05-27 14:16   ` [dpdk-dev] [PATCH v2 3/5] bpf: add support for packet data load instructions Konstantin Ananyev
2020-05-27 14:16   ` [dpdk-dev] [PATCH v2 4/5] test/bpf: add new test cases for mbuf " Konstantin Ananyev
2020-05-27 14:16   ` [dpdk-dev] [PATCH v2 5/5] bpf: x86 JIT support for packet data " Konstantin Ananyev
2020-05-28  8:50     ` Morten Brørup [this message]
2020-06-24 21:43   ` [dpdk-dev] [PATCH v2 0/5] bpf: add support for BPF_ABS/BPF_IND instructions Thomas Monjalon

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