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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, 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 D67B0C6379F for ; Thu, 19 Nov 2020 22:02:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FCE22222F for ; Thu, 19 Nov 2020 22:02:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726828AbgKSWCG (ORCPT ); Thu, 19 Nov 2020 17:02:06 -0500 Received: from mx2.suse.de ([195.135.220.15]:34968 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725877AbgKSWCF (ORCPT ); Thu, 19 Nov 2020 17:02:05 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6FFBAAC41; Thu, 19 Nov 2020 22:02:03 +0000 (UTC) Received: by lion.mk-sys.cz (Postfix, from userid 1000) id 13A59603F9; Thu, 19 Nov 2020 23:02:03 +0100 (CET) Date: Thu, 19 Nov 2020 23:02:03 +0100 From: Michal Kubecek To: tanhuazhong Cc: Andrew Lunn , davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linuxarm@huawei.com, kuba@kernel.org Subject: Re: [RFC net-next 1/2] ethtool: add support for controling the type of adaptive coalescing Message-ID: <20201119220203.fv2uluoeekyoyxrv@lion.mk-sys.cz> References: <1605758050-21061-1-git-send-email-tanhuazhong@huawei.com> <1605758050-21061-2-git-send-email-tanhuazhong@huawei.com> <20201119041557.GR1804098@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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