linux-kernel - Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices

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Message-ID: <20181115193201.GF4179@lahna.fi.intel.com>
Date:   Thu, 15 Nov 2018 21:32:01 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Yehezkel Bernat <yehezkelshb@...il.com>, lorenzo.pieralisi@....com,
        iommu@...ts.linux-foundation.org, joro@...tes.org,
        David Woodhouse <dwmw2@...radead.org>,
        baolu.lu@...ux.intel.com, ashok.raj@...el.com,
        Bjorn Helgaas <bhelgaas@...gle.com>, rjw@...ysocki.net,
        jacob.jun.pan@...el.com, Andreas Noever <andreas.noever@...il.com>,
        michael.jamet@...el.com, Christian Kellner <ckellner@...hat.com>,
        Mario Limonciello <Mario.Limonciello@...l.com>,
        Anthony Wong <anthony.wong@...onical.com>,
        linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices

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.