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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 E6515C43381 for ; Wed, 10 Mar 2021 02:23:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8D6D64F80 for ; Wed, 10 Mar 2021 02:23:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232135AbhCJCW5 (ORCPT ); Tue, 9 Mar 2021 21:22:57 -0500 Received: from mga18.intel.com ([134.134.136.126]:11702 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231299AbhCJCWh (ORCPT ); Tue, 9 Mar 2021 21:22:37 -0500 IronPort-SDR: LEY/aue7aBdfJgQIgJ5ZIpx/REIfSOgk1zN5RW5Xwomlu3hMab3uP7VSx/Zkai076lidHnMlpp POKb0uhepJyw== X-IronPort-AV: E=McAfee;i="6000,8403,9917"; a="175966622" X-IronPort-AV: E=Sophos;i="5.81,236,1610438400"; d="scan'208";a="175966622" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Mar 2021 18:22:35 -0800 IronPort-SDR: 4hb4GTO/VCURjcsMMoLIhUgrPjxB6ULiRRKXoeTZE+siy3Iy3gYkSIer46ao1JOZ1k65tnpHD7 gglQM2RcKfaw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,236,1610438400"; d="scan'208";a="376770074" Received: from unknown (HELO [10.239.154.55]) ([10.239.154.55]) by fmsmga007.fm.intel.com with ESMTP; 09 Mar 2021 18:22:30 -0800 Subject: Re: [PATCH v6] i2c: virtio: add a virtio i2c frontend driver To: Jason Wang , linux-i2c@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Cc: mst@redhat.com, wsa@kernel.org, wsa+renesas@sang-engineering.com, andriy.shevchenko@linux.intel.com, conghui.chen@intel.com, arnd@arndb.de, kblaiech@mellanox.com, jarkko.nikula@linux.intel.com, Sergey.Semin@baikalelectronics.ru, rppt@kernel.org, loic.poulain@linaro.org, tali.perry1@gmail.com, u.kleine-koenig@pengutronix.de, bjorn.andersson@linaro.org, yu1.wang@intel.com, shuo.a.liu@intel.com, viresh.kumar@linaro.org, stefanha@redhat.com, pbonzini@redhat.com References: <9a2086f37c0a62069b67c39a3f75941b78a0039c.1614749417.git.jie.deng@intel.com> <43b0842b-8b0f-1979-ed07-d6124e3a6b79@redhat.com> From: Jie Deng Message-ID: Date: Wed, 10 Mar 2021 10:22:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <43b0842b-8b0f-1979-ed07-d6124e3a6b79@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/3/4 17:15, Jason Wang wrote: > > >> +        } >> + >> +        if (msgs[i].flags & I2C_M_RD) >> +            memcpy(msgs[i].buf, req->buf, msgs[i].len); > > > Sorry if I had asked this before but any rason not to use msg[i].buf > directly? > > The msg[i].buf is passed by the I2C core. I just noticed that these bufs are not always allocated by kmalloc. They may come from the stack, which may cause the check "sg_init_one -> sg_set_buf -> virt_addr_valid"  to fail. Therefore the msg[i].buf is not suitable for direct use here. Regards.