linux-kernel - Re: [PATCH 4/4] pci: export untrusted attribute in sysfs

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Message-ID: <20200617073100.GA14424@infradead.org>
Date:   Wed, 17 Jun 2020 00:31:00 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-acpi@...r.kernel.org, Raj Ashok <ashok.raj@...el.com>,
        "Krishnakumar, Lalithambika" <lalithambika.krishnakumar@...el.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Prashant Malani <pmalani@...gle.com>,
        Benson Leung <bleung@...gle.com>,
        Todd Broch <tbroch@...gle.com>,
        Alex Levin <levinale@...gle.com>,
        Mattias Nissler <mnissler@...gle.com>,
        Rajat Jain <rajatxjain@...il.com>,
        Bernie Keany <bernie.keany@...el.com>,
        Aaron Durbin <adurbin@...gle.com>,
        Diego Rivas <diegorivas@...gle.com>,
        Duncan Laurie <dlaurie@...gle.com>,
        Furquan Shaikh <furquan@...gle.com>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Christian Kellner <christian@...lner.me>,
        Alex Williamson <alex.williamson@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Oliver O'Halloran <oohall@...il.com>
Subject: Re: [PATCH 4/4] pci: export untrusted attribute in sysfs

On Tue, Jun 16, 2020 at 12:27:35PM -0700, Rajat Jain wrote:
> Need clarification. The flag "untrusted" is currently a part of
> pci_dev struct, and is populated within the PCI subsystem.

Yes, and that is the problem.

> 
> 1) Is your suggestion to move this flag as well as the attribute to
> device core (in "struct device")? This would allow other buses to
> populate/use this flag if they want. By default it'll be set to 0 for
> all devices (PCI subsystem will populate it based on platform info,
> like it does today).
> 
> OR
> 
> 2) Are you suggesting to keep the "untrusted" flag within PCI, but
> attach the sysfs attribute to the base device? (&pci_dev->dev)?

(1).  As for IOMMUs and userspace policy it really should not matter
what bus a device is on if it is external and not trustworthy.