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=-15.7 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 B2378C2B9F4 for ; Mon, 14 Jun 2021 16:03:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 99B0C6120E for ; Mon, 14 Jun 2021 16:03:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234324AbhFNQFp (ORCPT ); Mon, 14 Jun 2021 12:05:45 -0400 Received: from foss.arm.com ([217.140.110.172]:39860 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233135AbhFNQFl (ORCPT ); Mon, 14 Jun 2021 12:05:41 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 932A21FB; Mon, 14 Jun 2021 09:03:38 -0700 (PDT) Received: from [10.57.9.136] (unknown [10.57.9.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D39653F70D; Mon, 14 Jun 2021 09:03:36 -0700 (PDT) Subject: Re: [PATCH v12 2/5] iommu: Enhance IOMMU default DMA mode build options To: John Garry , joro@8bytes.org, will@kernel.org, dwmw2@infradead.org, baolu.lu@linux.intel.com Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxarm@huawei.com, thunder.leizhen@huawei.com, chenxiang66@hisilicon.com References: <1623414043-40745-1-git-send-email-john.garry@huawei.com> <1623414043-40745-3-git-send-email-john.garry@huawei.com> From: Robin Murphy Message-ID: <2fe7d268-bc9f-9808-29a5-610527a0fd32@arm.com> Date: Mon, 14 Jun 2021 17:03:31 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <1623414043-40745-3-git-send-email-john.garry@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-06-11 13:20, John Garry wrote: > From: Zhen Lei > > First, add build options IOMMU_DEFAULT_{LAZY|STRICT}, so that we have the > opportunity to set {lazy|strict} mode as default at build time. Then put > the two config options in an choice, as they are mutually exclusive. > > [jpg: Make choice between strict and lazy only (and not passthrough)] > Signed-off-by: Zhen Lei > Signed-off-by: John Garry > --- > drivers/iommu/Kconfig | 38 ++++++++++++++++++++++++++++++++++++++ > drivers/iommu/iommu.c | 3 ++- > 2 files changed, 40 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index 1f111b399bca..2a71347611d4 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -90,6 +90,44 @@ config IOMMU_DEFAULT_PASSTHROUGH > > If unsure, say N here. > > +choice > + prompt "IOMMU default DMA mode" > + depends on IOMMU_DMA > + > + default IOMMU_DEFAULT_STRICT > + help > + This option allows an IOMMU DMA mode to be chosen at build time, to > + override the default DMA mode of each ARCH, removing the need to > + pass in kernel parameters through command line. It is still possible > + to provide ARCH-specific or common boot options to override this > + option. > + > + If unsure, keep the default. > + > +config IOMMU_DEFAULT_STRICT > + bool "strict" > + help > + For every IOMMU DMA unmap operation, the flush operation of IOTLB and > + the free operation of IOVA are guaranteed to be done in the unmap > + function. > + > +config IOMMU_DEFAULT_LAZY > + bool "lazy" > + help > + Support lazy mode, where for every IOMMU DMA unmap operation, the > + flush operation of IOTLB and the free operation of IOVA are deferred. > + They are only guaranteed to be done before the related IOVA will be > + reused. > + > + The isolation provided in this mode is not as secure as STRICT mode, > + such that a vulnerable time window may be created between the DMA > + unmap and the mapping finally being torn down in the IOMMU, where the > + device can still access the system memory. However this mode may > + provide better performance in high throughput scenarios, and is still > + considerably more secure than passthrough mode or no IOMMU. > + > +endchoice > + > config OF_IOMMU > def_bool y > depends on OF && IOMMU_API > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index cf58949cc2f3..ccbd5d4c1a50 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -29,7 +29,8 @@ static struct kset *iommu_group_kset; > static DEFINE_IDA(iommu_group_ida); > > static unsigned int iommu_def_domain_type __read_mostly; > -static bool iommu_dma_strict __read_mostly = true; > +static bool iommu_dma_strict __read_mostly = > + IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); Nit: I reckon this is a fine place to wield the 100-character relaxation, but it's not my call in the end. With the wording tweaks already mentioned, Reviewed-by: Robin Murphy > static u32 iommu_cmd_line __read_mostly; > > struct iommu_group { >