From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D116BC43381 for ; Tue, 19 Feb 2019 14:53:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9D522146E for ; Tue, 19 Feb 2019 14:53:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728312AbfBSOxG (ORCPT ); Tue, 19 Feb 2019 09:53:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54226 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726246AbfBSOxG (ORCPT ); Tue, 19 Feb 2019 09:53:06 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 316CF8762E; Tue, 19 Feb 2019 14:53:06 +0000 (UTC) Received: from carbon (ovpn-200-42.brq.redhat.com [10.40.200.42]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5E8DD61460; Tue, 19 Feb 2019 14:53:00 +0000 (UTC) Date: Tue, 19 Feb 2019 15:52:59 +0100 From: Jesper Dangaard Brouer To: Daniel Borkmann Cc: netdev@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , brouer@redhat.com Subject: Re: [PATCH bpf-next] bpf: add skb->queue_mapping write access from tc clsact Message-ID: <20190219155259.677d195c@carbon> In-Reply-To: <11d2572e-3ff5-2fc0-8f05-c50dd0fb1d6d@iogearbox.net> References: <155057184028.20935.11848804617158437103.stgit@firesoul> <11d2572e-3ff5-2fc0-8f05-c50dd0fb1d6d@iogearbox.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 19 Feb 2019 14:53:06 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 19 Feb 2019 12:46:57 +0100 Daniel Borkmann wrote: > On 02/19/2019 11:24 AM, Jesper Dangaard Brouer wrote: > > The skb->queue_mapping already have read access, via __sk_buff->queue_mapping. > > > > This patch allow BPF tc qdisc clsact write access to the queue_mapping via > > tc_cls_act_is_valid_access. > > > > It is already possible to change this via TC filter action skbedit > > tc-skbedit(8). Due to the lack of TC examples, lets show one: > > > > # tc qdisc add dev ixgbe1 handle ffff: ingress > > # tc filter add dev ixgbe1 parent ffff: matchall action skbedit queue_mapping 5 > > # tc filter list dev ixgbe1 parent ffff: > > Using handles was in the old days, if we add examples, then lets do > something more user friendly ;) > > # tc qdisc add dev ixgbe1 clsact > # tc filter replace dev ixgbe1 ingress matchall action skbedit queue_mapping 5 > # tc filter list dev ixgbe1 ingress > > > The most common mistake is that XPS (Transmit Packet Steering) takes > > precedence over setting skb->queue_mapping. XPS is configured per DEVICE > > via /sys/class/net/DEVICE/queues/tx-*/xps_cpus via a CPU hex mask. To > > disable set mask=00. > > > > The purpose of changing skb->queue_mapping is to influence the selection of > > the net_device "txq" (struct netdev_queue), which influence selection of > > the qdisc "root_lock" (via txq->qdisc->q.lock) and txq->_xmit_lock. When > > using the MQ qdisc the txq->qdisc points to different qdiscs and associated > > locks, and HARD_TX_LOCK (txq->_xmit_lock), allowing for CPU scalability. > > > > Due to lack of TC examples, lets show howto attach clsact BPF programs: > > > > # tc qdisc add dev ixgbe2 clsact > > # tc filter replace dev ixgbe2 egress bpf da obj XXX_kern.o sec tc_qmap2cpu > > # tc filter list dev ixgbe2 egress > > > > Signed-off-by: Jesper Dangaard Brouer > > --- > > net/core/filter.c | 14 +++++++++++--- > > 1 file changed, 11 insertions(+), 3 deletions(-) > > > > diff --git a/net/core/filter.c b/net/core/filter.c > > index 353735575204..d05ae8d05397 100644 > > --- a/net/core/filter.c > > +++ b/net/core/filter.c > > @@ -6238,6 +6238,7 @@ static bool tc_cls_act_is_valid_access(int off, int size, > > case bpf_ctx_range(struct __sk_buff, tc_classid): > > case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]): > > case bpf_ctx_range(struct __sk_buff, tstamp): > > + case bpf_ctx_range(struct __sk_buff, queue_mapping): > > break; > > default: > > return false; > > @@ -6642,9 +6643,16 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, > > break; > > > > case offsetof(struct __sk_buff, queue_mapping): > > - *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, > > - bpf_target_off(struct sk_buff, queue_mapping, 2, > > - target_size)); > > + if (type == BPF_WRITE) > > + *insn++ = BPF_STX_MEM(BPF_H, si->dst_reg, si->src_reg, > > + bpf_target_off(struct sk_buff, > > + queue_mapping, > > + 2, target_size)); > > + else > > + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, > > + bpf_target_off(struct sk_buff, > > + queue_mapping, > > + 2, target_size)); > > One thing we should avoid would be to allow user to write NO_QUEUE_MAPPING > into skb->queue_mapping so we don't hit the warn in sk_tx_queue_set(), I'd > add this into the ctx rewrite here. Makes sense. I would really appreciate if you could help me out writing the needed BPF instructions, as I'm not an expert here. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer