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 Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0EC23C433FE for ; Thu, 2 Dec 2021 17:26:31 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 989C96F4BF; Thu, 2 Dec 2021 17:26:31 +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 y-4cTqaz1CL5; Thu, 2 Dec 2021 17:26:30 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp3.osuosl.org (Postfix) with ESMTPS id 8F0D661CF6; Thu, 2 Dec 2021 17:26:30 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 7891FC001C; Thu, 2 Dec 2021 17:26:30 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 670CAC000A for ; Thu, 2 Dec 2021 17:26:29 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 55A9F6F4BB for ; Thu, 2 Dec 2021 17:26:29 +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 WgS_6gquabAU for ; Thu, 2 Dec 2021 17:26:27 +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 5C5EA61CF6 for ; Thu, 2 Dec 2021 17:26:27 +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 72E80142F; Thu, 2 Dec 2021 09:26:26 -0800 (PST) Received: from [10.57.34.58] (unknown [10.57.34.58]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 350B63F73B; Thu, 2 Dec 2021 09:26:24 -0800 (PST) Message-ID: Date: Thu, 2 Dec 2021 17:26:19 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH v4 04/14] Documentation/x86: Secure Launch kernel documentation Content-Language: en-GB To: Ross Philipson , linux-kernel@vger.kernel.org, x86@kernel.org, iommu@lists.linux-foundation.org, linux-integrity@vger.kernel.org, linux-doc@vger.kernel.org References: <1630070917-9896-1-git-send-email-ross.philipson@oracle.com> <1630070917-9896-5-git-send-email-ross.philipson@oracle.com> From: Robin Murphy In-Reply-To: <1630070917-9896-5-git-send-email-ross.philipson@oracle.com> Cc: dpsmith@apertussolutions.com, luto@amacapital.net, mingo@redhat.com, kanth.ghatraju@oracle.com, hpa@zytor.com, bp@alien8.de, tglx@linutronix.de, trenchboot-devel@googlegroups.com 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2021-08-27 14:28, Ross Philipson wrote: [...] > +IOMMU Configuration > +------------------- > + > +When doing a Secure Launch, the IOMMU should always be enabled and the drivers > +loaded. However, IOMMU passthrough mode should never be used. This leaves the > +MLE completely exposed to DMA after the PMR's [2]_ are disabled. First, IOMMU > +passthrough should be disabled by default in the build configuration:: > + > + "Device Drivers" --> > + "IOMMU Hardware Support" --> > + "IOMMU passthrough by default [ ]" > + > +This unset the Kconfig value CONFIG_IOMMU_DEFAULT_PASSTHROUGH. Note that the config structure has now changed, and if set, passthrough is deselected by choosing a different default domain type. > +In addition, passthrough must be disabled on the kernel command line when doing > +a Secure Launch as follows:: > + > + iommu=nopt iommu.passthrough=0 This part is a bit silly - those options are literally aliases for the exact same thing, and furthermore if the config is already set as required then the sole effect either of them will have is to cause "(set by kernel command line)" to be printed. There is no value in explicitly overriding the default value with the default value - if anyone can append an additional "iommu.passthrough=1" (or "iommu=pt") to the end of the command line they'll still win. Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu