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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CAC0EC4338F for ; Fri, 30 Jul 2021 09:30:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B015661042 for ; Fri, 30 Jul 2021 09:30:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238174AbhG3JaH (ORCPT ); Fri, 30 Jul 2021 05:30:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49538 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238095AbhG3JaG (ORCPT ); Fri, 30 Jul 2021 05:30:06 -0400 Received: from mail-ed1-x52c.google.com (mail-ed1-x52c.google.com [IPv6:2a00:1450:4864:20::52c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EC02C061765 for ; Fri, 30 Jul 2021 02:30:00 -0700 (PDT) Received: by mail-ed1-x52c.google.com with SMTP id da26so12288678edb.1 for ; Fri, 30 Jul 2021 02:30:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=yTXTqt76E4GEU0UK9YFMo0iaEiN8YMEQ//FwGWJRdeg=; b=C7Xuhg0pbaQmCiRVNt5VksbzD8WVUhyFEf6KeaNTEN+U3PyTN3dpnBfFK3jLX8ZwJp ZL2zwsy7erQuGwXn/6N1MZoJlSY9SCfrfMfGfYjKeexYeWWG9lc+kojub516EvyABeEP sxB3l+l8nxURaym6t6Bjv2rMHMMrTHZIZLhk34zbBH7kUCe+zp5u0niVEF1OYU7cdoXW 1rTx1UikZmr81qzeHaNZAA9jgtZWF0/tR7+DuDX8uNx/o48ahUKv8rv0mHhIqcG7iZj9 6lwDTNRMB5mxbWW997/PixT6YuEqw2SE/sM4iPN29nLO5vsCkj2gpRZb+73tcMLxY3My iU3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=yTXTqt76E4GEU0UK9YFMo0iaEiN8YMEQ//FwGWJRdeg=; b=baTpip+fI4k/0O1rwb99cYtOqOjq2t4Lx6x/7yFKv4lywl2IE0uQXiqciqsrCsC18R Wq6yxXvPYDbuGcsXjlg/tlk9qfI1NVOTRYlTiO2mrmuoUtirJxzqTwtQbkCgXEHiGIPu G/YNeHAnV3AlddYqlLThM/nj486zcciZMkxw3PlABs+WGiI1ae8alc9P7ufJ1Y1PrNQk FrTYljk+gDdzfzSEmVeOoHoDgmT3vucDwNmubrS/C4+0Rwvix8ecq2QSiixcf8FlDCcm y9NXYXJEdKf4KWk0degny04aD+7vZ4NoLuKU/zpe+6ele4ETY3DLrEfyGkPdEI1qVZRP L3qg== X-Gm-Message-State: AOAM531ye3HGZaDfSYhVM0ygdIFH1NSKLOLa5tgYeVkGR5e0ncfmsPLV loqcaGTYYhu3MnFPzjomJjHUxrJ2sHysQA== X-Google-Smtp-Source: ABdhPJzR7h7K0UB04ngaRLs+lx+K56tBTUTPTr94qqq9WbBrSm9ijUbX3qk7TivlvyjJfwpw5LhteQ== X-Received: by 2002:a50:cf8c:: with SMTP id h12mr1827098edk.360.1627637398976; Fri, 30 Jul 2021 02:29:58 -0700 (PDT) Received: from myrica (adsl-84-226-111-173.adslplus.ch. [84.226.111.173]) by smtp.gmail.com with ESMTPSA id c13sm422187edv.93.2021.07.30.02.29.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Jul 2021 02:29:58 -0700 (PDT) Date: Fri, 30 Jul 2021 11:29:38 +0200 From: Jean-Philippe Brucker To: Robin Murphy Cc: joro@8bytes.org, will@kernel.org, linux-kernel@vger.kernel.org, dianders@chromium.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs Message-ID: References: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 28, 2021 at 04:58:41PM +0100, Robin Murphy wrote: > To parallel the sysfs behaviour, merge the new build-time option > for DMA domain strictness into the default domain type choice. > > Suggested-by: Joerg Roedel > Signed-off-by: Robin Murphy kernel-parameters.txt still refers to the old config options Otherwise Reviewed-by: Jean-Philippe Brucker > --- > drivers/iommu/Kconfig | 80 +++++++++++++++++++++---------------------- > drivers/iommu/iommu.c | 2 +- > 2 files changed, 41 insertions(+), 41 deletions(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index c84da8205be7..6e06f876d75a 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -79,55 +79,55 @@ config IOMMU_DEBUGFS > debug/iommu directory, and then populate a subdirectory with > entries as required. > > -config IOMMU_DEFAULT_PASSTHROUGH > - bool "IOMMU passthrough by default" > - depends on IOMMU_API > - help > - Enable passthrough by default, removing the need to pass in > - iommu.passthrough=on or iommu=pt through command line. If this > - is enabled, you can still disable with iommu.passthrough=off > - or iommu=nopt depending on the architecture. > - > - If unsure, say N here. > - > choice > - prompt "IOMMU default DMA IOTLB invalidation mode" > - depends on IOMMU_DMA > - > - default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU) > - default IOMMU_DEFAULT_STRICT > + prompt "IOMMU default domain type" > + depends on IOMMU_API > + default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU > + default IOMMU_DEFAULT_DMA_STRICT > help > - This option allows an IOMMU DMA IOTLB invalidation mode to be > - chosen at build time, to override the default mode of each ARCH, > - removing the need to pass in kernel parameters through command line. > - It is still possible to provide common boot params to override this > - config. > + Choose the type of IOMMU domain used to manage DMA API usage by > + device drivers. The options here typically represent different > + levels of tradeoff between robustness/security and performance, > + depending on the IOMMU driver. Not all IOMMUs support all options. > + This choice can be overridden at boot via the command line, and for > + some devices also at runtime via sysfs. > > If unsure, keep the default. > > -config IOMMU_DEFAULT_STRICT > - bool "strict" > +config IOMMU_DEFAULT_DMA_STRICT > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent > + to passing "iommu.passthrough=0 iommu.strict=1" on the command line. > > -config IOMMU_DEFAULT_LAZY > - bool "lazy" > + Untrusted devices always use this mode, with an additional layer of > + bounce-buffering such that they cannot gain access to any unrelated > + data within a mapped page. > + > +config IOMMU_DEFAULT_DMA_LAZY > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, but with "lazy" batched TLB invalidation. This > + mode allows higher performance with some IOMMUs due to reduced TLB > + flushing, but at the cost of reduced isolation since devices may be > + able to access memory for some time after it has been unmapped. > + Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the > + command line. > > - 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 mappings cached in the IOMMU IOTLB or device TLB > - finally being invalidated, where the device could still access the > - memory which has already been unmapped by the device driver. > - However this mode may provide better performance in high throughput > - scenarios, and is still considerably more secure than passthrough > - mode or no IOMMU. > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > + > +config IOMMU_DEFAULT_PASSTHROUGH > + bool "Passthrough" > + help > + Trusted devices are identity-mapped, giving them unrestricted access > + to memory with minimal performance overhead. Equivalent to passing > + "iommu.passthrough=1" (historically "iommu=pt") on the command line. > + > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > > endchoice > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 5a08e0806cbb..25c1adc1ec67 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -31,7 +31,7 @@ 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 = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); > +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT); > static u32 iommu_cmd_line __read_mostly; > > struct iommu_group { > -- > 2.25.1 > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C654FC4338F for ; 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[84.226.111.173]) by smtp.gmail.com with ESMTPSA id c13sm422187edv.93.2021.07.30.02.29.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Jul 2021 02:29:58 -0700 (PDT) Date: Fri, 30 Jul 2021 11:29:38 +0200 From: Jean-Philippe Brucker To: Robin Murphy Subject: Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs Message-ID: References: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> Cc: linux-kernel@vger.kernel.org, dianders@chromium.org, iommu@lists.linux-foundation.org, will@kernel.org, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Jul 28, 2021 at 04:58:41PM +0100, Robin Murphy wrote: > To parallel the sysfs behaviour, merge the new build-time option > for DMA domain strictness into the default domain type choice. > > Suggested-by: Joerg Roedel > Signed-off-by: Robin Murphy kernel-parameters.txt still refers to the old config options Otherwise Reviewed-by: Jean-Philippe Brucker > --- > drivers/iommu/Kconfig | 80 +++++++++++++++++++++---------------------- > drivers/iommu/iommu.c | 2 +- > 2 files changed, 41 insertions(+), 41 deletions(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index c84da8205be7..6e06f876d75a 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -79,55 +79,55 @@ config IOMMU_DEBUGFS > debug/iommu directory, and then populate a subdirectory with > entries as required. > > -config IOMMU_DEFAULT_PASSTHROUGH > - bool "IOMMU passthrough by default" > - depends on IOMMU_API > - help > - Enable passthrough by default, removing the need to pass in > - iommu.passthrough=on or iommu=pt through command line. If this > - is enabled, you can still disable with iommu.passthrough=off > - or iommu=nopt depending on the architecture. > - > - If unsure, say N here. > - > choice > - prompt "IOMMU default DMA IOTLB invalidation mode" > - depends on IOMMU_DMA > - > - default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU) > - default IOMMU_DEFAULT_STRICT > + prompt "IOMMU default domain type" > + depends on IOMMU_API > + default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU > + default IOMMU_DEFAULT_DMA_STRICT > help > - This option allows an IOMMU DMA IOTLB invalidation mode to be > - chosen at build time, to override the default mode of each ARCH, > - removing the need to pass in kernel parameters through command line. > - It is still possible to provide common boot params to override this > - config. > + Choose the type of IOMMU domain used to manage DMA API usage by > + device drivers. The options here typically represent different > + levels of tradeoff between robustness/security and performance, > + depending on the IOMMU driver. Not all IOMMUs support all options. > + This choice can be overridden at boot via the command line, and for > + some devices also at runtime via sysfs. > > If unsure, keep the default. > > -config IOMMU_DEFAULT_STRICT > - bool "strict" > +config IOMMU_DEFAULT_DMA_STRICT > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent > + to passing "iommu.passthrough=0 iommu.strict=1" on the command line. > > -config IOMMU_DEFAULT_LAZY > - bool "lazy" > + Untrusted devices always use this mode, with an additional layer of > + bounce-buffering such that they cannot gain access to any unrelated > + data within a mapped page. > + > +config IOMMU_DEFAULT_DMA_LAZY > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, but with "lazy" batched TLB invalidation. This > + mode allows higher performance with some IOMMUs due to reduced TLB > + flushing, but at the cost of reduced isolation since devices may be > + able to access memory for some time after it has been unmapped. > + Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the > + command line. > > - 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 mappings cached in the IOMMU IOTLB or device TLB > - finally being invalidated, where the device could still access the > - memory which has already been unmapped by the device driver. > - However this mode may provide better performance in high throughput > - scenarios, and is still considerably more secure than passthrough > - mode or no IOMMU. > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > + > +config IOMMU_DEFAULT_PASSTHROUGH > + bool "Passthrough" > + help > + Trusted devices are identity-mapped, giving them unrestricted access > + to memory with minimal performance overhead. Equivalent to passing > + "iommu.passthrough=1" (historically "iommu=pt") on the command line. > + > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > > endchoice > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 5a08e0806cbb..25c1adc1ec67 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -31,7 +31,7 @@ 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 = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); > +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT); > static u32 iommu_cmd_line __read_mostly; > > struct iommu_group { > -- > 2.25.1 > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-14.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B4205C4338F for ; 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[84.226.111.173]) by smtp.gmail.com with ESMTPSA id c13sm422187edv.93.2021.07.30.02.29.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Jul 2021 02:29:58 -0700 (PDT) Date: Fri, 30 Jul 2021 11:29:38 +0200 From: Jean-Philippe Brucker To: Robin Murphy Cc: joro@8bytes.org, will@kernel.org, linux-kernel@vger.kernel.org, dianders@chromium.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs Message-ID: References: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210730_023001_732767_5EA36721 X-CRM114-Status: GOOD ( 40.39 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 28, 2021 at 04:58:41PM +0100, Robin Murphy wrote: > To parallel the sysfs behaviour, merge the new build-time option > for DMA domain strictness into the default domain type choice. > > Suggested-by: Joerg Roedel > Signed-off-by: Robin Murphy kernel-parameters.txt still refers to the old config options Otherwise Reviewed-by: Jean-Philippe Brucker > --- > drivers/iommu/Kconfig | 80 +++++++++++++++++++++---------------------- > drivers/iommu/iommu.c | 2 +- > 2 files changed, 41 insertions(+), 41 deletions(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index c84da8205be7..6e06f876d75a 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -79,55 +79,55 @@ config IOMMU_DEBUGFS > debug/iommu directory, and then populate a subdirectory with > entries as required. > > -config IOMMU_DEFAULT_PASSTHROUGH > - bool "IOMMU passthrough by default" > - depends on IOMMU_API > - help > - Enable passthrough by default, removing the need to pass in > - iommu.passthrough=on or iommu=pt through command line. If this > - is enabled, you can still disable with iommu.passthrough=off > - or iommu=nopt depending on the architecture. > - > - If unsure, say N here. > - > choice > - prompt "IOMMU default DMA IOTLB invalidation mode" > - depends on IOMMU_DMA > - > - default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU) > - default IOMMU_DEFAULT_STRICT > + prompt "IOMMU default domain type" > + depends on IOMMU_API > + default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU > + default IOMMU_DEFAULT_DMA_STRICT > help > - This option allows an IOMMU DMA IOTLB invalidation mode to be > - chosen at build time, to override the default mode of each ARCH, > - removing the need to pass in kernel parameters through command line. > - It is still possible to provide common boot params to override this > - config. > + Choose the type of IOMMU domain used to manage DMA API usage by > + device drivers. The options here typically represent different > + levels of tradeoff between robustness/security and performance, > + depending on the IOMMU driver. Not all IOMMUs support all options. > + This choice can be overridden at boot via the command line, and for > + some devices also at runtime via sysfs. > > If unsure, keep the default. > > -config IOMMU_DEFAULT_STRICT > - bool "strict" > +config IOMMU_DEFAULT_DMA_STRICT > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent > + to passing "iommu.passthrough=0 iommu.strict=1" on the command line. > > -config IOMMU_DEFAULT_LAZY > - bool "lazy" > + Untrusted devices always use this mode, with an additional layer of > + bounce-buffering such that they cannot gain access to any unrelated > + data within a mapped page. > + > +config IOMMU_DEFAULT_DMA_LAZY > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, but with "lazy" batched TLB invalidation. This > + mode allows higher performance with some IOMMUs due to reduced TLB > + flushing, but at the cost of reduced isolation since devices may be > + able to access memory for some time after it has been unmapped. > + Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the > + command line. > > - 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 mappings cached in the IOMMU IOTLB or device TLB > - finally being invalidated, where the device could still access the > - memory which has already been unmapped by the device driver. > - However this mode may provide better performance in high throughput > - scenarios, and is still considerably more secure than passthrough > - mode or no IOMMU. > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > + > +config IOMMU_DEFAULT_PASSTHROUGH > + bool "Passthrough" > + help > + Trusted devices are identity-mapped, giving them unrestricted access > + to memory with minimal performance overhead. Equivalent to passing > + "iommu.passthrough=1" (historically "iommu=pt") on the command line. > + > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > > endchoice > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 5a08e0806cbb..25c1adc1ec67 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -31,7 +31,7 @@ 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 = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); > +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT); > static u32 iommu_cmd_line __read_mostly; > > struct iommu_group { > -- > 2.25.1 > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel