From patchwork Mon Nov 26 11:15:26 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mika Westerberg X-Patchwork-Id: 10697999 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2B62E13AD for ; Mon, 26 Nov 2018 11:15:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1BB6E28935 for ; Mon, 26 Nov 2018 11:15:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0FE2328A17; Mon, 26 Nov 2018 11:15:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7722F28935 for ; Mon, 26 Nov 2018 11:15:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730027AbeKZWJ2 (ORCPT ); Mon, 26 Nov 2018 17:09:28 -0500 Received: from mga03.intel.com ([134.134.136.65]:44833 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730328AbeKZWJW (ORCPT ); Mon, 26 Nov 2018 17:09:22 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Nov 2018 03:15:33 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,281,1539673200"; d="scan'208";a="111288271" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga001.fm.intel.com with ESMTP; 26 Nov 2018 03:15:27 -0800 Received: by black.fi.intel.com (Postfix, from userid 1001) id 0B0E8591; Mon, 26 Nov 2018 13:15:27 +0200 (EET) From: Mika Westerberg To: iommu@lists.linux-foundation.org Cc: Joerg Roedel , David Woodhouse , Lu Baolu , Ashok Raj , Bjorn Helgaas , "Rafael J. Wysocki" , Jacob jun Pan , Andreas Noever , Michael Jamet , Yehezkel Bernat , Lukas Wunner , Christian Kellner , Mario.Limonciello@dell.com, Anthony Wong , Lorenzo Pieralisi , Christoph Hellwig , Alex Williamson , Mika Westerberg , linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 4/4] thunderbolt: Export IOMMU based DMA protection support to userspace Date: Mon, 26 Nov 2018 14:15:26 +0300 Message-Id: <20181126111526.56340-5-mika.westerberg@linux.intel.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181126111526.56340-1-mika.westerberg@linux.intel.com> References: <20181126111526.56340-1-mika.westerberg@linux.intel.com> MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Recent systems with Thunderbolt ports may support IOMMU natively. In practice this means that Thunderbolt connected devices are placed behind an IOMMU during the whole time it is connected (including during boot) making Thunderbolt security levels redundant. This is called Kernel DMA protection [1] by Microsoft. Some of these systems still have Thunderbolt security level set to "user" in order to support OS downgrade (the older version of the OS might not support IOMMU based DMA protection so connecting a device still relies on user approval). Export this information to userspace by introducing a new sysfs attribute (iommu_dma_protection). Based on it userspace tools can make more accurate decision whether or not authorize the connected device. In addition update Thunderbolt documentation regarding IOMMU based DMA protection. [1] https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt Signed-off-by: Mika Westerberg Reviewed-by: Yehezkel Bernat --- .../ABI/testing/sysfs-bus-thunderbolt | 9 +++++++++ Documentation/admin-guide/thunderbolt.rst | 20 +++++++++++++++++++ drivers/thunderbolt/domain.c | 17 ++++++++++++++++ 3 files changed, 46 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-thunderbolt b/Documentation/ABI/testing/sysfs-bus-thunderbolt index 151584a1f950..b21fba14689b 100644 --- a/Documentation/ABI/testing/sysfs-bus-thunderbolt +++ b/Documentation/ABI/testing/sysfs-bus-thunderbolt @@ -21,6 +21,15 @@ Description: Holds a comma separated list of device unique_ids that If a device is authorized automatically during boot its boot attribute is set to 1. +What: /sys/bus/thunderbolt/devices/.../domainX/iommu_dma_protection +Date: Mar 2019 +KernelVersion: 4.21 +Contact: thunderbolt-software@lists.01.org +Description: This attribute tells whether the system uses IOMMU + for DMA protection. Value of 1 means IOMMU is used 0 means + it is not (DMA protection is solely based on Thunderbolt + security levels). + What: /sys/bus/thunderbolt/devices/.../domainX/security Date: Sep 2017 KernelVersion: 4.13 diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst index 35fccba6a9a6..9158d66f04a4 100644 --- a/Documentation/admin-guide/thunderbolt.rst +++ b/Documentation/admin-guide/thunderbolt.rst @@ -133,6 +133,26 @@ If the user still wants to connect the device they can either approve the device without a key or write a new key and write 1 to the ``authorized`` file to get the new key stored on the device NVM. +DMA protection utilizing IOMMU +------------------------------ +Recent systems from 2018 and forward with Thunderbolt ports may natively +support IOMMU. This means that Thunderbolt security is handled by an IOMMU +so connected devices cannot access memory regions outside of what is +allocated for them by drivers. When Linux is running on such system it +automatically enables IOMMU if not enabled by the user already. These +systems can be identified by reading ``1`` from +``/sys/bus/thunderbolt/devices/domainX/iommu_dma_protection`` attribute. + +The driver does not do anything special in this case but because DMA +protection is handled by the IOMMU, security levels (if set) are +redundant. For this reason some systems ship with security level set to +``none``. Other systems have security level set to ``user`` in order to +support downgrade to older OS, so users who want to automatically +authorize devices when IOMMU DMA protection is enabled can use the +following ``udev`` rule:: + + ACTION=="add", SUBSYSTEM=="thunderbolt", ATTRS{iommu_dma_protection}=="1", ATTR{authorized}=="0", ATTR{authorized}="1" + Upgrading NVM on Thunderbolt device or host ------------------------------------------- Since most of the functionality is handled in firmware running on a diff --git a/drivers/thunderbolt/domain.c b/drivers/thunderbolt/domain.c index 93e562f18d40..7416bdbd8576 100644 --- a/drivers/thunderbolt/domain.c +++ b/drivers/thunderbolt/domain.c @@ -7,7 +7,9 @@ */ #include +#include #include +#include #include #include #include @@ -236,6 +238,20 @@ static ssize_t boot_acl_store(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR_RW(boot_acl); +static ssize_t iommu_dma_protection_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + /* + * Kernel DMA protection is a feature where Thunderbolt security is + * handled natively using IOMMU. It is enabled when IOMMU is + * enabled and ACPI DMAR table has DMAR_PLATFORM_OPT_IN set. + */ + return sprintf(buf, "%d\n", + iommu_present(&pci_bus_type) && dmar_platform_optin()); +} +static DEVICE_ATTR_RO(iommu_dma_protection); + static ssize_t security_show(struct device *dev, struct device_attribute *attr, char *buf) { @@ -251,6 +267,7 @@ static DEVICE_ATTR_RO(security); static struct attribute *domain_attrs[] = { &dev_attr_boot_acl.attr, + &dev_attr_iommu_dma_protection.attr, &dev_attr_security.attr, NULL, };