From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out2.migadu.com (out2.migadu.com [IPv6:2001:41d0:2:aacc::]) by mail.toke.dk (Postfix) with ESMTPS id 3E8EA9B415D for ; Mon, 7 Nov 2022 23:02:02 +0100 (CET) Authentication-Results: mail.toke.dk; dkim=pass (1024-bit key; unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=nalMmdEX Message-ID: <187e89c3-d7de-7bec-c72e-d9d6eb5bcca0@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1667858519; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5Lah0aa6diJhPNTAGAxAtQxlp7AX+K4kMo28ZVTFjP4=; b=nalMmdEXcuy725S/fF0nTT8AYked5sz3xF+1Hfy1Qf9qxTVYRb7naxYvdMyq0I/QpYlW5V lrpPbCs6nleKeP76+OtiKREylLKdWlLWrp1llS0UmLWOe2rPh4yPJP0L38fhMnhrmTXD5N +40TdZskWeTLwjvO10qUVlBtn7YZ0JE= Date: Mon, 7 Nov 2022 14:01:53 -0800 MIME-Version: 1.0 Content-Language: en-US To: Stanislav Fomichev References: <20221104032532.1615099-1-sdf@google.com> <20221104032532.1615099-7-sdf@google.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: <20221104032532.1615099-7-sdf@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Message-ID-Hash: GVULPLW5AH3PNG7CNYGZJEWO57RPIOSX X-Message-ID-Hash: GVULPLW5AH3PNG7CNYGZJEWO57RPIOSX X-MailFrom: martin.lau@linux.dev X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org, David Ahern , Jakub Kicinski , Willem de Bruijn , Jesper Dangaard Brouer , Anatoly Burakov , Alexander Lobakin , Magnus Karlsson , Maryam Tahhan , xdp-hints@xdp-project.net, netdev@vger.kernel.org, bpf@vger.kernel.org X-Mailman-Version: 3.3.5 Precedence: list Subject: [xdp-hints] Re: [RFC bpf-next v2 06/14] xdp: Carry over xdp metadata into skb context List-Id: XDP hardware hints design discussion Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 11/3/22 8:25 PM, Stanislav Fomichev wrote: > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 59c9fd55699d..dba857f212d7 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -4217,9 +4217,13 @@ static inline bool skb_metadata_differs(const struct sk_buff *skb_a, > true : __skb_metadata_differs(skb_a, skb_b, len_a); > } > > +void skb_metadata_import_from_xdp(struct sk_buff *skb, size_t len); > + > static inline void skb_metadata_set(struct sk_buff *skb, u8 meta_len) > { > skb_shinfo(skb)->meta_len = meta_len; > + if (meta_len) > + skb_metadata_import_from_xdp(skb, meta_len); > } > [ ... ] > +struct xdp_to_skb_metadata { > + u32 magic; /* xdp_metadata_magic */ > + u64 rx_timestamp; > +} __randomize_layout; > + > +struct bpf_patch; > + [ ... ] > +void skb_metadata_import_from_xdp(struct sk_buff *skb, size_t len) > +{ > + struct xdp_to_skb_metadata *meta = (void *)(skb_mac_header(skb) - len); > + > + /* Optional SKB info, currently missing: > + * - HW checksum info (skb->ip_summed) > + * - HW RX hash (skb_set_hash) > + * - RX ring dev queue index (skb_record_rx_queue) > + */ > + > + if (len != sizeof(struct xdp_to_skb_metadata)) > + return; > + > + if (meta->magic != xdp_metadata_magic) > + return; > + > + if (meta->rx_timestamp) { > + *skb_hwtstamps(skb) = (struct skb_shared_hwtstamps){ > + .hwtstamp = ns_to_ktime(meta->rx_timestamp), > + }; > + } > +} Considering the metadata will affect the gro, should the meta be cleared after importing to the skb? [ ... ] > +/* Since we're not actually doing a call but instead rewriting > + * in place, we can only afford to use R0-R5 scratch registers. > + * > + * We reserve R1 for bpf_xdp_metadata_export_to_skb and let individual > + * metadata kfuncs use only R0,R4-R5. > + * > + * The above also means we _cannot_ easily call any other helper/kfunc > + * because there is no place for us to preserve our R1 argument; > + * existing R6-R9 belong to the callee. > + */ > +void xdp_metadata_export_to_skb(const struct bpf_prog *prog, struct bpf_patch *patch) > +{ > + u32 func_id; > + > + /* > + * The code below generates the following: > + * > + * void bpf_xdp_metadata_export_to_skb(struct xdp_md *ctx) > + * { > + * struct xdp_to_skb_metadata *meta; > + * int ret; > + * > + * ret = bpf_xdp_adjust_meta(ctx, -sizeof(*meta)); > + * if (!ret) > + * return; > + * > + * meta = ctx->data_meta; > + * meta->magic = xdp_metadata_magic; > + * meta->rx_timestamp = bpf_xdp_metadata_rx_timestamp(ctx); > + * } > + * > + */ > + > + bpf_patch_append(patch, > + /* r2 = ((struct xdp_buff *)r1)->data_meta; */ > + BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, > + offsetof(struct xdp_buff, data_meta)), > + /* r3 = ((struct xdp_buff *)r1)->data; */ > + BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_1, > + offsetof(struct xdp_buff, data)), > + /* if (data_meta != data) return; > + * > + * data_meta > data: xdp_data_meta_unsupported() > + * data_meta < data: already used, no need to touch > + */ > + BPF_JMP_REG(BPF_JNE, BPF_REG_2, BPF_REG_3, S16_MAX), > + > + /* r2 -= sizeof(struct xdp_to_skb_metadata); */ > + BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, > + sizeof(struct xdp_to_skb_metadata)), > + /* r3 = ((struct xdp_buff *)r1)->data_hard_start; */ > + BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_1, > + offsetof(struct xdp_buff, data_hard_start)), > + /* r3 += sizeof(struct xdp_frame) */ > + BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, > + sizeof(struct xdp_frame)), > + /* if (data-sizeof(struct xdp_to_skb_metadata) < data_hard_start+sizeof(struct xdp_frame)) return; */ > + BPF_JMP_REG(BPF_JLT, BPF_REG_2, BPF_REG_3, S16_MAX), > + > + /* ((struct xdp_buff *)r1)->data_meta = r2; */ > + BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, > + offsetof(struct xdp_buff, data_meta)), > + > + /* *((struct xdp_to_skb_metadata *)r2)->magic = xdp_metadata_magic; */ > + BPF_ST_MEM(BPF_W, BPF_REG_2, > + offsetof(struct xdp_to_skb_metadata, magic), > + xdp_metadata_magic), > + ); > + > + /* r0 = bpf_xdp_metadata_rx_timestamp(ctx); */ > + func_id = xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_TIMESTAMP); > + prog->aux->xdp_kfunc_ndo->ndo_unroll_kfunc(prog, func_id, patch); > + > + bpf_patch_append(patch, > + /* r2 = ((struct xdp_buff *)r1)->data_meta; */ > + BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, > + offsetof(struct xdp_buff, data_meta)), > + /* *((struct xdp_to_skb_metadata *)r2)->rx_timestamp = r0; */ > + BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_0, > + offsetof(struct xdp_to_skb_metadata, rx_timestamp)), Can the xdp prog still change the metadata through xdp->data_meta? tbh, I am not sure it is solid enough by asking the xdp prog not to use the same random number in its own metadata + not to change the metadata through xdp->data_meta after calling bpf_xdp_metadata_export_to_skb(). Does xdp_to_skb_metadata have a use case for XDP_PASS (like patch 7) or the xdp_to_skb_metadata can be limited to XDP_REDIRECT only? > + ); > + > + bpf_patch_resolve_jmp(patch); > +} > + > static int __init xdp_metadata_init(void) > { > + xdp_metadata_magic = get_random_u32() | 1; > return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &xdp_metadata_kfunc_set); > } > late_initcall(xdp_metadata_init);