linux-kernel - Re: [PATCH] PCI: ACPI: Allow internal devices to be marked as untrusted

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Message-ID: <YfOf2X7Snm7cvDRV@lahna>
Date:   Fri, 28 Jan 2022 09:48:41 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rajat Jain <rajatxjain@...il.com>,
        Dmitry Torokhov <dtor@...gle.com>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Pavel Machek <pavel@...x.de>,
        Oliver O'Halloran <oohall@...il.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] PCI: ACPI: Allow internal devices to be marked as
 untrusted

Hi,

On Thu, Jan 27, 2022 at 02:26:07PM -0800, Rajat Jain wrote:
> Hello Rafael, Bjorn, Mika, Dmitry, Greg,
> 
> Thanks a lot for your comments.
> 
> On Tue, Jan 25, 2022 at 6:45 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > On Tue, Jan 25, 2022 at 1:55 PM Mika Westerberg
> > <mika.westerberg@...ux.intel.com> wrote:
> > >
> > > On Tue, Jan 25, 2022 at 12:15:02PM +0100, Greg Kroah-Hartman wrote:
> > > > On Tue, Jan 25, 2022 at 12:58:52PM +0200, Mika Westerberg wrote:
> > > > > On Mon, Jan 24, 2022 at 08:27:17AM +0200, Mika Westerberg wrote:
> > > > > > > > This patch introduces a new "UntrustedDevice" property that can be used
> > > > > > > > by the firmware to mark any device as untrusted.
> > > > > >
> > > > > > I think this new property should be documented somewhere too (also
> > > > > > explain when to use it instead of ExternalFacingPort). If not in the
> > > > > > next ACPI spec or some supplemental doc then perhaps in the DT bindings
> > > > > > under Documentation/devicetree/bindings.
> > > > >
> > > > > Actually Microsoft has similar already:
> > > > >
> > > > > https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-internal-pcie-ports-accessible-to-users-and-requiring-dma-protection
> > > > >
> > > > > I think we should use that too here.
> 
> But because this property also applies to a root port (only), it only
> helps if the device is downstream a PCIe root port. In our case, we
> have an internal (wifi) device 00:14.3 (sits on the internal PCI bus
> 0), so cannot use this.

Right. I wonder if we can expand it to cover all internal devices, not
just PCIe root ports? We anyways need to support that property so does
not make much sense to me to invent yet another that does pretty much
the same thing.