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

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Date:   Thu, 18 Jun 2020 18:39:25 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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>,
        ACPI Devel Maling List <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>,
        "Oliver O'Halloran" <oohall@...il.com>
Subject: Re: [PATCH 4/4] pci: export untrusted attribute in sysfs

On Thu, Jun 18, 2020 at 6:04 PM Rajat Jain <rajatja@...gle.com> wrote:
> On Thu, Jun 18, 2020 at 2:14 AM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:

...

> To clarify, the attribute exposed by the firmware today is
> "ExternalFacingPort" and "external-facing" respectively:
>
> 617654aae50e ("PCI / ACPI: Identify untrusted PCI devices")
> 9cb30a71ac45d("PCI: OF: Support "external-facing" property")
>
> The kernel flag was named "untrusted" though, hence the assumption
> that "external=untrusted" is currently baked into the kernel today.
> IMHO, using "external" would fix that (The assumption can thus be
> contained in the IOMMU drivers) and at the same time allow more use of
> this attribute.

That discussion had been held, IIRC, during introduction of the
untrusted member in struct pci_dev...

> > > Trust is different, yes, don't get the two mixed up please.  That should
> > > be a different sysfs attribute for obvious reasons.
> >
> > Yes, as a bottom line that's what I meant as well.
>
> So what is the consensus here? I don't have a strong opinion - but it
> seemed to me Greg is saying "external" and Andy is saying "untrusted"?

...and a conclusion has been made as you may see. So, I would highly
recommend to speak to the author(s) of the patch that introduced /
adopted 'untrusted' member.

-- 
With Best Regards,
Andy Shevchenko