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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15A76C001DF for ; Tue, 1 Aug 2023 17:39:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229618AbjHARj2 (ORCPT ); Tue, 1 Aug 2023 13:39:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42942 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229379AbjHARj0 (ORCPT ); Tue, 1 Aug 2023 13:39:26 -0400 Received: from mgamail.intel.com (unknown [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A417E53; Tue, 1 Aug 2023 10:39:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1690911565; x=1722447565; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version:content-transfer-encoding; bh=UonUIoBUCNktB5rB1/gE9ziHWmQHQrb//uJtkHY7PGw=; b=lZuNKAh+9xnIyMr4GI1x5LN53eSdHufxbIcODJ8r5jGSeJ3ND9Kbb//q LZhuqTUY8LFwFxnD9LOSsoYch3YwgfBWoahfpenW5f9aNUQtT0d/YBY4m iFqEJew0HXvVmXpnhvOhhdrff7l6oMDWjAaOl0xXZKKzKFI2bgffceH+a bzBlY0GaE+6/reJAgLDHHQPmxJuUc9WQRyY/OTV+Pmr1PvQUJiLJxduA7 oUyM/151hkLxXEmPoygcXEbUAfOgWGfNm5ttZWQWV05cJ6olK9zOtJmA4 gxtFdUZFhGcBoeUuQM7QSK5l3B3eCo6xF8OY4H6GRSRvOk9ImPFS8UdYX A==; X-IronPort-AV: E=McAfee;i="6600,9927,10789"; a="368270365" X-IronPort-AV: E=Sophos;i="6.01,247,1684825200"; d="scan'208";a="368270365" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Aug 2023 10:39:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.01,202,1684825200"; d="scan'208";a="872149547" Received: from vcostago-desk1.jf.intel.com (HELO vcostago-desk1) ([10.54.70.17]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Aug 2023 10:39:26 -0700 From: Vinicius Costa Gomes To: Vladimir Oltean Cc: netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jamal Hadi Salim , Cong Wang , Jiri Pirko , linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org, Muhammad Husaini Zulkifli , Peilin Ye , Pedro Tammela , Richard Cochran , Zhengchao Shao , Maxim Georgiev Subject: Re: [PATCH v2 net-next 7/9] net: netdevsim: mimic tc-taprio offload In-Reply-To: <20230801164534.2nklcql2nh6x6p7y@skbuf> References: <20230613215440.2465708-1-vladimir.oltean@nxp.com> <20230613215440.2465708-8-vladimir.oltean@nxp.com> <877cs5twqn.fsf@intel.com> <20230801164534.2nklcql2nh6x6p7y@skbuf> Date: Tue, 01 Aug 2023 10:39:23 -0700 Message-ID: <87o7jq64s4.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vladimir, Vladimir Oltean writes: > On Wed, Jun 14, 2023 at 05:06:24PM -0700, Vinicius Costa Gomes wrote: >> > +static int nsim_setup_tc_taprio(struct net_device *dev, >> > + struct tc_taprio_qopt_offload *offload) >> > +{ >> > + int err =3D 0; >> > + >> > + switch (offload->cmd) { >> > + case TAPRIO_CMD_REPLACE: >> > + case TAPRIO_CMD_DESTROY: >> > + break; >>=20 >> I was thinking about how useful would proper validation of the >> parameters be? Thinking that we could detect "driver API" breakages >> earlier, and we want it documented that the drivers should check for the >> things that it supports. >>=20 >> Makes sense? > > Sorry, I lack imagination as to what the netdevsim driver may check for. > The taprio offload parameters should always be valid, properly speaking, > otherwise the Qdisc wouldn't be passing them on to the driver. At least > that would be the intention. The rest are hardware specific checks for > hardware specific limitations. Here there is no hardware. > Trying to remember what was going through my mind when I said that. What I seem to recall is something that would help us "keep honest": I was worrying about someone (perhaps myself ;-) sneaking a new feature in taprio and forgetting to update other drivers. I thought that adding a check for the existing parameters would help detect those kind of things. If anything unknown was there in the offload struct, netdevsim would complain loudly. Perhaps I was worrying too much. And the way to solve that is to keep active attention against that during review. > The parameters passed to TAPRIO_CMD_REPLACE are: > > struct tc_mqprio_qopt_offload mqprio: > struct tc_mqprio_qopt qopt: validated by taprio_parse_mqprio_opt() for f= lags 0x2 > u16 mode: always set to TC_MQPRIO_MODE_DCB > u16 shaper: always set to TC_MQPRIO_SHAPER_DCB > u32 flags: always set to 0 > u64 min_rate[TC_QOPT_MAX_QUEUE]: always set to [0,] > u64 max_rate[TC_QOPT_MAX_QUEUE]: always set to [0,] > unsigned long preemptible_tcs: always set to 0, because ethtool_dev_mm_s= upported() returns false > > ktime_t base_time: any value is valid > > u64 cycle_time: any value is valid > > u64 cycle_time_extension: any value <=3D cycle_time is valid. According t= o 802.1Q > "Q.5 CycleTimeExtension variables", it's the maximum > amount by which the penultimate cycle can be extended > to avoid a very short cycle upon a ConfigChange event. > But if CycleTimeExtension is larger than one CycleTime, > then we're not even talking about the penultimate cycle > anymore, but about ones previous to that?! Maybe this > should be limited to 0 <=3D cycle_time_extension <=3D cycle_time > by taprio, certainly not by offloading drivers. > Good point. I have to review 802.1Q, but from what I remember that sounds right, cycle_time_extension greater than cycle_time doesn't make much sense. Having a check for it in taprio itself sounds good. > u32 max_sdu[TC_MAX_QUEUE]: limited to a value <=3D dev->max_mtu by taprio > > size_t num_entries: any value is valid > > struct tc_taprio_sched_entry entries[]: > u8 command: will be either one of: TC_TAPRIO_CMD_SET_GATES, TC_TAPRIO_CM= D_SET_AND_HOLD > or TC_TAPRIO_CMD_SET_AND_RELEASE. However 802.1Q "Table 8-7=E2=80= =94Gate operations" > says "If frame preemption is not supported or not enabled (preempti= onActive is > FALSE), this operation behaves the same as SetGateStates.". So I > see no reason to enforce any restriction here either? > > u32 gate_mask: technically can have bits set, which correspond > to traffic classes larger than dev->num_tc. > Taprio can enforce this, so I wouldn't see > drivers beginning to feel paranoid about it. > Actually I had a patch about this: > https://patchwork.kernel.org/project/netdevbpf/patch/20230130173= 145.475943-15-vladimir.oltean@nxp.com/ > but I decided to drop it because I didn't have > any strong case for it. > u32 interval: any value is valid. If the sum of entry intervals > is less than the cycle_time, again that's taprio's > problem to check for, in its netlink attribute > validation method rather than offloading drivers. > Thank you for the time it took to give this amount of detail. Cheers, --=20 Vinicius