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=unavailable 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 43281C49EA2 for ; Mon, 21 Jun 2021 05:17:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1FF2261042 for ; Mon, 21 Jun 2021 05:17:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229661AbhFUFTr (ORCPT ); Mon, 21 Jun 2021 01:19:47 -0400 Received: from mga06.intel.com ([134.134.136.31]:49645 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbhFUFTq (ORCPT ); Mon, 21 Jun 2021 01:19:46 -0400 IronPort-SDR: 3hn5S7zWgrUGkcg3Ypl98Hf5aaL8yznB6a2V7+IgnT1r+syQJsuQIhR0FkiPui0rbiWWoPSJ3j gF5YmjyyXxrA== X-IronPort-AV: E=McAfee;i="6200,9189,10021"; a="267919629" X-IronPort-AV: E=Sophos;i="5.83,289,1616482800"; d="scan'208";a="267919629" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jun 2021 22:17:32 -0700 IronPort-SDR: 9Xxri7XJd9v6KBQMO9fhv7VvxtB0dH0OGtBQ4S0a8I7KOm46M0mLtWytuAniowgdp2Wya2YagJ ed//po5RjGhA== X-IronPort-AV: E=Sophos;i="5.83,289,1616482800"; d="scan'208";a="453761991" Received: from blu2-mobl3.ccr.corp.intel.com (HELO [10.254.211.249]) ([10.254.211.249]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jun 2021 22:17:29 -0700 Cc: baolu.lu@linux.intel.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxarm@huawei.com, thunder.leizhen@huawei.com, chenxiang66@hisilicon.com, linux-doc@vger.kernel.org To: John Garry , joro@8bytes.org, will@kernel.org, dwmw2@infradead.org, robin.murphy@arm.com, corbet@lwn.net References: <1624016058-189713-1-git-send-email-john.garry@huawei.com> <1624016058-189713-7-git-send-email-john.garry@huawei.com> From: Lu Baolu Subject: Re: [PATCH v14 6/6] iommu: Remove mode argument from iommu_set_dma_strict() Message-ID: Date: Mon, 21 Jun 2021 13:17:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <1624016058-189713-7-git-send-email-john.garry@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/6/18 19:34, John Garry wrote: > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 60b1ec42e73b..ff221d3ddcbc 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -349,10 +349,9 @@ static int __init iommu_dma_setup(char *str) > } > early_param("iommu.strict", iommu_dma_setup); > > -void iommu_set_dma_strict(bool strict) > +void iommu_set_dma_strict(void) > { > - if (strict || !(iommu_cmd_line & IOMMU_CMD_LINE_STRICT)) > - iommu_dma_strict = strict; > + iommu_dma_strict = true; > } Sorry for this late comment. Normally the cache invalidation policy should come from the user. We have pre-build kernel option and also a kernel boot command iommu.strict to override it. These seem reasonable. We also have a helper (iommu_set_dma_strict()) so that the vendor iommu driver could squeeze in and change the previous settings mostly due to: a) vendor iommu driver specific kernel boot command. (We are about to deprecate those.) b) quirky hardware. c) kernel optimization (e.x. strict mode in VM environment). a) and b) are mandatory, while c) is optional. In any instance should c) override the flush mode specified by the user. Hence, probably we should also have another helper like: void iommu_set_dma_strict_optional() { if (!(iommu_cmd_line & IOMMU_CMD_LINE_STRICT)) iommu_dma_strict = true; } Any thoughts? Best regards, baolu