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=-17.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 18DCDC432BE for ; Tue, 17 Aug 2021 11:53:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E842D60E78 for ; Tue, 17 Aug 2021 11:53:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236992AbhHQLy3 (ORCPT ); Tue, 17 Aug 2021 07:54:29 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3655 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236693AbhHQLy2 (ORCPT ); Tue, 17 Aug 2021 07:54:28 -0400 Received: from fraeml744-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4GpqD04WDBz6BGJN; Tue, 17 Aug 2021 19:53:04 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml744-chm.china.huawei.com (10.206.15.225) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Tue, 17 Aug 2021 13:53:53 +0200 Received: from [10.202.227.179] (10.202.227.179) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.8; Tue, 17 Aug 2021 12:53:53 +0100 Subject: Re: [PATCH] iommu/arm-smmu-v3: Stop pre-zeroing batch commands in arm_smmu_atc_inv_master() To: Zhen Lei , Will Deacon , Robin Murphy , Joerg Roedel , linux-arm-kernel , iommu , References: <20210817113411.1962-1-thunder.leizhen@huawei.com> From: John Garry Message-ID: <23f1cc66-2172-9534-53ef-3d9b2db26bda@huawei.com> Date: Tue, 17 Aug 2021 12:53:52 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20210817113411.1962-1-thunder.leizhen@huawei.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.179] X-ClientProxiedBy: lhreml702-chm.china.huawei.com (10.201.108.51) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/08/2021 12:34, Zhen Lei wrote: > Pre-zeroing the batched commands structure is inefficient, as individual > commands are zeroed later in arm_smmu_cmdq_build_cmd(). Therefore, only > the member 'num' needs to be initialized to 0. > > Signed-off-by: Zhen Lei Reviewed-by: John Garry > --- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > index 50a9db5bac466c7..e6882ae81fd08f6 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > @@ -1776,10 +1776,11 @@ static int arm_smmu_atc_inv_master(struct arm_smmu_master *master) > { > int i; > struct arm_smmu_cmdq_ent cmd; > - struct arm_smmu_cmdq_batch cmds = {}; > + struct arm_smmu_cmdq_batch cmds; > > arm_smmu_atc_inv_to_cmd(0, 0, 0, &cmd); > > + cmds.num = 0; We prob should have added a comment why we do this (and at the other sites). I think Robin said something similar in another patch. > for (i = 0; i < master->num_streams; i++) { > cmd.atc.sid = master->streams[i].id; > arm_smmu_cmdq_batch_add(master->smmu, &cmds, &cmd); >