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=-5.5 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 4409CC49361 for ; Fri, 18 Jun 2021 07:37:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A52F61396 for ; Fri, 18 Jun 2021 07:37:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233296AbhFRHjm (ORCPT ); Fri, 18 Jun 2021 03:39:42 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3265 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233264AbhFRHjf (ORCPT ); Fri, 18 Jun 2021 03:39:35 -0400 Received: from fraeml712-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4G5r5Q1d3Jz6GB6f; Fri, 18 Jun 2021 15:24:10 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml712-chm.china.huawei.com (10.206.15.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 18 Jun 2021 09:37:22 +0200 Received: from [10.47.95.81] (10.47.95.81) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 18 Jun 2021 08:37:21 +0100 Subject: Re: [PATCH v13 4/6] iommu/vt-d: Add support for IOMMU default DMA mode build options To: Lu Baolu , , , , , CC: , , , , , References: <1623841437-211832-1-git-send-email-john.garry@huawei.com> <1623841437-211832-5-git-send-email-john.garry@huawei.com> <46dbce5c-1c2b-60d4-df56-d2b95a959425@linux.intel.com> From: John Garry Message-ID: Date: Fri, 18 Jun 2021 08:31:05 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.47.95.81] X-ClientProxiedBy: lhreml743-chm.china.huawei.com (10.201.108.193) 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 18/06/2021 02:46, Lu Baolu wrote: Hi baolu, >> I need to change that. How about this: >> >> bool print_warning = false; >> >> for_each_active_iommu(iommu, drhd) { >>      /* >>       * The flush queue implementation does not perform >>       * page-selective invalidations that are required for efficient >>       * TLB flushes in virtual environments.  The benefit of batching >>       * is likely to be much lower than the overhead of synchronizing >>       * the virtual and physical IOMMU page-tables. >>       */ >>      if (!print_warning && cap_caching_mode(iommu->cap)) { >>          pr_warn("IOMMU batching disallowed due to virtualization\n"); >>          iommu_set_dma_strict(true); >>          print_warning = true; >>      } >>      ... >> } >> >> or use pr_warn_once(). > > From my p.o.v, pr_xxxx_once() is better. > > How about using a pr_info_once()? I don't think it's a warning, it's > just a policy choice in VM environment. ok, I can go with that, which Robin mostly agrees with. Thanks, John