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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E19A1C388F9 for ; Fri, 20 Nov 2020 01:52:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B49B22255 for ; Fri, 20 Nov 2020 01:52:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727032AbgKTBwW (ORCPT ); Thu, 19 Nov 2020 20:52:22 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:7657 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726122AbgKTBwW (ORCPT ); Thu, 19 Nov 2020 20:52:22 -0500 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Ccfg73RRJz15KdD; Fri, 20 Nov 2020 09:52:03 +0800 (CST) Received: from [127.0.0.1] (10.74.149.191) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.487.0; Fri, 20 Nov 2020 09:52:11 +0800 Subject: Re: [RFC net-next 1/2] ethtool: add support for controling the type of adaptive coalescing To: Michal Kubecek CC: Andrew Lunn , , , , , References: <1605758050-21061-1-git-send-email-tanhuazhong@huawei.com> <1605758050-21061-2-git-send-email-tanhuazhong@huawei.com> <20201119041557.GR1804098@lunn.ch> <20201119220203.fv2uluoeekyoyxrv@lion.mk-sys.cz> From: tanhuazhong Message-ID: Date: Fri, 20 Nov 2020 09:52:10 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20201119220203.fv2uluoeekyoyxrv@lion.mk-sys.cz> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.74.149.191] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/20 6:02, Michal Kubecek wrote: > On Thu, Nov 19, 2020 at 04:56:42PM +0800, tanhuazhong wrote: >> On 2020/11/19 12:15, Andrew Lunn wrote: >>>> diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h >>>> index 9ca87bc..afd8de2 100644 >>>> --- a/include/uapi/linux/ethtool.h >>>> +++ b/include/uapi/linux/ethtool.h >>>> @@ -433,6 +433,7 @@ struct ethtool_modinfo { >>>> * a TX interrupt, when the packet rate is above @pkt_rate_high. >>>> * @rate_sample_interval: How often to do adaptive coalescing packet rate >>>> * sampling, measured in seconds. Must not be zero. >>>> + * @use_dim: Use DIM for IRQ coalescing, if adaptive coalescing is enabled. >>>> * >>>> * Each pair of (usecs, max_frames) fields specifies that interrupts >>>> * should be coalesced until >>>> @@ -483,6 +484,7 @@ struct ethtool_coalesce { >>>> __u32 tx_coalesce_usecs_high; >>>> __u32 tx_max_coalesced_frames_high; >>>> __u32 rate_sample_interval; >>>> + __u32 use_dim; >>>> }; >>> >>> You cannot do this. >>> >>> static noinline_for_stack int ethtool_set_coalesce(struct net_device *dev, >>> void __user *useraddr) >>> { >>> struct ethtool_coalesce coalesce; >>> int ret; >>> >>> if (!dev->ethtool_ops->set_coalesce) >>> return -EOPNOTSUPP; >>> >>> if (copy_from_user(&coalesce, useraddr, sizeof(coalesce))) >>> return -EFAULT; >>> >>> An old ethtool binary is not going to set this extra last byte to >>> anything meaningful. You cannot tell if you have an old or new user >>> space, so you have no idea if it put anything into use_dim, or if it >>> is random junk. > > Even worse, as there is no indication of data length, ETHTOOL_GCOALESCE > ioctl request from old ethtool on new kernel would result in kernel > writing past the end of userspace buffer. > >>> You have to leave the IOCTL interface unchanged, and limit this new >>> feature to the netlink API. >>> >> >> Hi, Andrew. >> thanks for pointing out this problem, i will fix it. >> without callling set_coalesce/set_coalesce of ethtool_ops, do you have any >> suggestion for writing/reading this new attribute to/from the driver? add a >> new field in net_device or a new callback function in ethtool_ops seems not >> good. > > We could use a similar approach as struct ethtool_link_ksettings, e.g. > > struct kernel_ethtool_coalesce { > struct ethtool_coalesce base; > /* new members which are not part of UAPI */ > } > > get_coalesce() and set_coalesce() would get pointer to struct > kernel_ethtool_coalesce and ioctl code would be modified to only touch > the base (legacy?) part. > Thanks for your suggestion. i will implement it in V2. > While already changing the ops arguments, we could also add extack > pointer, either as a separate argument or as struct member (I slightly > prefer the former). > > BtW, please don't forget to update the message descriptions in > Documentation/networking/ethtool-netlink.rst > > Michal > will update the doc in V2. Thanks. Huazhong. > . >