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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDC2FC433F5 for ; Tue, 5 Apr 2022 14:59:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234056AbiDEPA4 (ORCPT ); Tue, 5 Apr 2022 11:00:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44384 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379485AbiDENNo (ORCPT ); Tue, 5 Apr 2022 09:13:44 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4577D10782B; Tue, 5 Apr 2022 05:15:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1649160956; x=1680696956; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=eLlXIWgzT4jg7igfmDa9mpSj+r1W/DMEJ9zt2e+BDk4=; b=BROFxVoaMdJ9K3TW78g89ECva9COhsR+KZdSIpNuB+CplyS31FqpO7KS f+Zm8dbgsvviWO1GUchRhbsi/1kokykUjP1y4U/EyTtDEw42dYU75wCu3 3X5Ptdp6q1WLlWcrqBe32i5YI1H9KD68oIkJLwql2cLkbqBSRi8mKkK6b 0nPcCcdUzoSG91pJYUKZu161QQ24tTkQX3sZC+RlsRxN/PZKY9fh7QPq0 IVsopk/QFZ/K/+32GBkMd1ifAu9XYmQE9/ioSSCBc+yzhWPhx500Ml1cR NMAMur2fpbInQJex6lxim03Np6JG9U1SrmDYabBz4JwP8nZf9+TN1ntpT g==; X-IronPort-AV: E=McAfee;i="6200,9189,10307"; a="248249151" X-IronPort-AV: E=Sophos;i="5.90,236,1643702400"; d="scan'208";a="248249151" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Apr 2022 05:15:55 -0700 X-IronPort-AV: E=Sophos;i="5.90,236,1643702400"; d="scan'208";a="505260917" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.162]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Apr 2022 05:15:51 -0700 Received: by lahna (sSMTP sendmail emulation); Tue, 05 Apr 2022 15:09:07 +0300 Date: Tue, 5 Apr 2022 15:09:07 +0300 From: Mika Westerberg To: Robin Murphy Cc: joro@8bytes.org, baolu.lu@linux.intel.com, andreas.noever@gmail.com, michael.jamet@intel.com, YehezkelShB@gmail.com, iommu@lists.linux-foundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, mario.limonciello@amd.com, hch@lst.de Subject: Re: [PATCH v3 3/4] thunderbolt: Make iommu_dma_protection more accurate Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Apr 05, 2022 at 11:41:03AM +0100, Robin Murphy wrote: > Between me trying to get rid of iommu_present() and Mario wanting to > support the AMD equivalent of DMAR_PLATFORM_OPT_IN, scrutiny has shown > that the iommu_dma_protection attribute is being far too optimistic. > Even if an IOMMU might be present for some PCI segment in the system, > that doesn't necessarily mean it provides translation for the device(s) > we care about. Furthermore, all that DMAR_PLATFORM_OPT_IN really does > is tell us that memory was protected before the kernel was loaded, and > prevent the user from disabling the intel-iommu driver entirely. While > that lets us assume kernel integrity, what matters for actual runtime > DMA protection is whether we trust individual devices, based on the > "external facing" property that we expect firmware to describe for > Thunderbolt ports. > > It's proven challenging to determine the appropriate ports accurately > given the variety of possible topologies, so while still not getting a > perfect answer, by putting enough faith in firmware we can at least get > a good bit closer. If we can see that any device near a Thunderbolt NHI > has all the requisites for Kernel DMA Protection, chances are that it > *is* a relevant port, but moreover that implies that firmware is playing > the game overall, so we'll use that to assume that all Thunderbolt ports > should be correctly marked and thus will end up fully protected. > > CC: Mario Limonciello > Reviewed-by: Christoph Hellwig > Signed-off-by: Robin Murphy Acked-by: Mika Westerberg