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Date:   Thu, 15 Nov 2018 21:32:01 +0200
From:   Mika Westerberg <mika.westerberg@linux.intel.com>
To:     Lukas Wunner <lukas@wunner.de>
Cc:     Yehezkel Bernat <yehezkelshb@gmail.com>, lorenzo.pieralisi@arm.com,
        iommu@lists.linux-foundation.org, joro@8bytes.org,
        David Woodhouse <dwmw2@infradead.org>,
        baolu.lu@linux.intel.com, ashok.raj@intel.com,
        Bjorn Helgaas <bhelgaas@google.com>, rjw@rjwysocki.net,
        jacob.jun.pan@intel.com, Andreas Noever <andreas.noever@gmail.com>,
        michael.jamet@intel.com, Christian Kellner <ckellner@redhat.com>,
        Mario Limonciello <Mario.Limonciello@dell.com>,
        Anthony Wong <anthony.wong@canonical.com>,
        linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices
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On Thu, Nov 15, 2018 at 08:27:41PM +0100, Lukas Wunner wrote:
> On Thu, Nov 15, 2018 at 09:10:26PM +0200, Mika Westerberg wrote:
> > I was thinking we could cover all these with is_external filling them
> > based on the _DSD or some other means in the kernel.
> > 
> > We would then deal all such devices as "untrusted" by default.
> 
> Tinfoil hat on, even internal devices could be malicious.
> What's the downside of enabling the feature for everything?

Mostly performance, I think. That's the main reason we put all non
external devices to passthrough IOMMU mode.