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Date:   Sat, 27 Jun 2020 07:02:25 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Rajat Jain <rajatja@google.com>
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
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        Len Brown <lenb@kernel.org>, iommu@lists.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Raj Ashok <ashok.raj@intel.com>,
        "Krishnakumar, Lalithambika" <lalithambika.krishnakumar@intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Prashant Malani <pmalani@google.com>,
        Benson Leung <bleung@google.com>,
        Todd Broch <tbroch@google.com>,
        Alex Levin <levinale@google.com>,
        Mattias Nissler <mnissler@google.com>,
        Rajat Jain <rajatxjain@gmail.com>,
        Bernie Keany <bernie.keany@intel.com>,
        Aaron Durbin <adurbin@google.com>,
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        Christian Kellner <christian@kellner.me>,
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        Oliver O'Halloran <oohall@gmail.com>
Subject: Re: [PATCH 2/2] pci: Add parameter to disable attaching untrusted
 devices
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On Fri, Jun 26, 2020 at 11:53:34AM -0700, Rajat Jain wrote:
> a) I think what was decided was introducing a device core "location"
> property that can be exposed to userspace to help it to decide whether
> or not to attach a driver to a device. Yes, that is still the plan.

Great, but this patch ignores that and starts to add policy :(

> (Mild sidenote: userspace may not need to distinguish between internal
> and external devices if it can assume that no internal PCI devices
> will show up after "echo 0 > /sys/bus/pci/drivers_autoprobe". But
> nevertheless...)

It can not assume that.

> b) Note that even with (a) in place, we still need a parameter that
> can ensure that drivers are not bound to external devices at boot,
> *before* userspace gets a chance to disable "drivers_autoprobe".

Why do you think you need that?  I kind of doubt you really want this,
but ick, if you really do, make it a policy decision that you bake into
the kernel as a build option, so that no one else has to use it :)

> https://lkml.org/lkml/2020/6/15/1453

Ick, please use lore.kernel.org, we don't control lkml.org and it's not
all that reliable.

> Is it OK to add such a parameter in device core?

You don't have internal/external/wherever in the driver core yet, so
don't start adding policy before you get that...

thanks,

greg k-h