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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 8002CC4338F for ; Wed, 28 Jul 2021 16:00:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 683F360F93 for ; Wed, 28 Jul 2021 16:00:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237448AbhG1QAJ (ORCPT ); Wed, 28 Jul 2021 12:00:09 -0400 Received: from foss.arm.com ([217.140.110.172]:59562 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236701AbhG1P7n (ORCPT ); Wed, 28 Jul 2021 11:59:43 -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 A721711B3; Wed, 28 Jul 2021 08:59:41 -0700 (PDT) Received: from 010265703453.arm.com (unknown [10.57.36.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 35FC03F70D; Wed, 28 Jul 2021 08:59:40 -0700 (PDT) From: Robin Murphy To: joro@8bytes.org, will@kernel.org Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suravee.suthikulpanit@amd.com, baolu.lu@linux.intel.com, john.garry@huawei.com, dianders@chromium.org Subject: [PATCH v2 20/24] iommu: Merge strictness and domain type configs Date: Wed, 28 Jul 2021 16:58:41 +0100 Message-Id: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 2993AC432BE for ; Wed, 28 Jul 2021 15:59:48 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EA41B61039 for ; Wed, 28 Jul 2021 15:59:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org EA41B61039 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id C5B2083A73; Wed, 28 Jul 2021 15:59:47 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id J2Q2OhLKHyYd; Wed, 28 Jul 2021 15:59:46 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp1.osuosl.org (Postfix) with ESMTPS id 76CE8839CF; Wed, 28 Jul 2021 15:59:46 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 40CC8C001A; Wed, 28 Jul 2021 15:59:46 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [IPv6:2605:bc80:3010::136]) by lists.linuxfoundation.org (Postfix) with ESMTP id E9967C001A for ; Wed, 28 Jul 2021 15:59:42 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id E6C6A60892 for ; Wed, 28 Jul 2021 15:59:42 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xF0DZlJVrHD2 for ; Wed, 28 Jul 2021 15:59:42 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp3.osuosl.org (Postfix) with ESMTP id 0F0336089B for ; Wed, 28 Jul 2021 15:59:42 +0000 (UTC) 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 A721711B3; Wed, 28 Jul 2021 08:59:41 -0700 (PDT) Received: from 010265703453.arm.com (unknown [10.57.36.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 35FC03F70D; Wed, 28 Jul 2021 08:59:40 -0700 (PDT) From: Robin Murphy To: joro@8bytes.org, will@kernel.org Subject: [PATCH v2 20/24] iommu: Merge strictness and domain type configs Date: Wed, 28 Jul 2021 16:58:41 +0100 Message-Id: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Cc: linux-kernel@vger.kernel.org, dianders@chromium.org, iommu@lists.linux-foundation.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" 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 --- 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=-17.5 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, USER_AGENT_GIT 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 E7E55C4320A for ; Wed, 28 Jul 2021 16:11:45 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B8F9E61019 for ; Wed, 28 Jul 2021 16:11:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B8F9E61019 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=HFRxQTMmG6Q6n4T00BJsWqXUvbZhET1jgEOMVAfGmpg=; b=hdl7MyI3TunUlM DScc2n8bYlylZST8Z3BY9QU0AErFHaurwDahL6BCoVSMuwPgsnhsc+iyI0a6LRpRUB3A9vgo2yRyh cxwj0VmGEHQq8H6WqZDhLCF3gCyQS/8rJ7rFGBE3o7afU2jev9VvWy75DXo1SM9CL2/85Ng2xpNpq O2sSGLr7D2TDd4LQ3rSFsrPM4A3/GW9G7fKcWAwg7weC5Y0jjN79hbcjY6Ku4uq8cExHg2DjuI65r Lh/7IM+H/dvKaK8qP78hr2cVk+ziPa67It7qNmilpSzl4cQEDAdQBWkTHG8NYLmsQEIPhnsbQwKti 8p58QS+PjByI5Z45g29A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m8m7x-001VGv-1k; Wed, 28 Jul 2021 16:09:49 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m8ly9-001PNr-TB for linux-arm-kernel@lists.infradead.org; Wed, 28 Jul 2021 15:59:44 +0000 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 A721711B3; Wed, 28 Jul 2021 08:59:41 -0700 (PDT) Received: from 010265703453.arm.com (unknown [10.57.36.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 35FC03F70D; Wed, 28 Jul 2021 08:59:40 -0700 (PDT) From: Robin Murphy To: joro@8bytes.org, will@kernel.org Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suravee.suthikulpanit@amd.com, baolu.lu@linux.intel.com, john.garry@huawei.com, dianders@chromium.org Subject: [PATCH v2 20/24] iommu: Merge strictness and domain type configs Date: Wed, 28 Jul 2021 16:58:41 +0100 Message-Id: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210728_085942_067230_5338A306 X-CRM114-Status: GOOD ( 23.05 ) 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 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 --- 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel