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From: Rajat Jain <rajatja@google.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Joerg Roedel <joro@8bytes.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <lenb@kernel.org>,
	"open list:AMD IOMMU (AMD-VI)" <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>,
	Diego Rivas <diegorivas@google.com>,
	Duncan Laurie <dlaurie@google.com>,
	Furquan Shaikh <furquan@google.com>,
	Jesse Barnes <jsbarnes@google.com>,
	Christian Kellner <christian@kellner.me>,
	Alex Williamson <alex.williamson@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Oliver O'Halloran" <oohall@gmail.com>,
	Saravana Kannan <saravanak@google.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>
Subject: Re: [PATCH v2 2/7] PCI: Set "untrusted" flag for truly external devices only
Date: Mon, 6 Jul 2020 16:40:40 -0700
Message-ID: <CACK8Z6F9zGrOAQ9QQ0Wjt9zbPk3cPnjSTvoZsS_i_Rd0H6Uiiw@mail.gmail.com> (raw)
In-Reply-To: <20200706233040.GA169334@bjorn-Precision-5520>

Hello Bjorn,

On Mon, Jul 6, 2020 at 4:30 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Mon, Jul 06, 2020 at 03:31:47PM -0700, Rajat Jain wrote:
> > On Mon, Jul 6, 2020 at 9:38 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > On Mon, Jun 29, 2020 at 09:49:38PM -0700, Rajat Jain wrote:
>
> > > > -static void pci_acpi_set_untrusted(struct pci_dev *dev)
> > > > +static void pci_acpi_set_external_facing(struct pci_dev *dev)
> > > >  {
> > > >       u8 val;
> > > >
> > > > -     if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT)
> > > > +     if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT &&
> > > > +         pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM)
> > >
> > > This looks like a change worthy of its own patch.  We used to look for
> > > "ExternalFacingPort" only on Root Ports; now we'll also do it for
> > > Switch Downstream Ports.
> >
> > Can do. (please see below)
> >
> > > Can you include DT and ACPI spec references if they exist?  I found
> > > this mention:
> > > https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports
> > > which actually says it should only be implemented for Root Ports.
> >
> > I actually have no references. It seems to me that the microsoft spec
> > assumes that all external ports must be implemented on root ports, but
> > I think it would be equally fair for systems with PCIe switches to
> > implement one on one of their switch downstream ports. I don't have an
> > immediate use of this anyway, so if you think this should rather wait
> > unless someone really has this case, this can wait. Let me know.
>
> I agree that it "makes sense" to pay attention to this property no
> matter where it appears, but since that Microsoft doc went to the
> trouble to restrict it to Root Ports, I think we should leave this
> as-is and only look for it in the Root Port.  Otherwise Linux will
> accept something Windows will reject, and that seems like a needless
> difference.
>
> We can at least include the above link to the Microsoft doc in the
> commit log.

Will do.

>
> > > It also mentions a "DmaProperty" that looks related.  Maybe Linux
> > > should also pay attention to this?
> >
> > Interesting. Since this is not in use currently by the kernel as well
> > as not exposed by (our) BIOS, I don't have an immediate use case for
> > this. I'd like to defer this for later (as-the-need-arises).
>
> I agree, you can defer this until you see a need for it.  I just
> pointed it out in case it would be useful to you.
>
> > > > +     /*
> > > > +      * Devices are marked as external-facing using info from platform
> > > > +      * (ACPI / devicetree). An external-facing device is still an internal
> > > > +      * trusted device, but it faces external untrusted devices. Thus any
> > > > +      * devices enumerated downstream an external-facing device is marked
> > > > +      * as untrusted.
> > >
> > > This comment has a subject/verb agreement problem.
> >
> > I assume you meant s/is/are/ in last sentence. Will do.
>
> Right.  There's also something wrong with "enumerated downstream an".

I'm apparently really bad at English :-). This is what I have in my
latest patch I am about to send out:

"Thus any device enumerated downstream an external-facing device, is
marked as untrusted."

Are you suggesting s/an/a/ ? Please let me know what you would like to
see and I'd copy it as-is :-)

Thanks!

Rajat

  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30  4:49 [PATCH v2 0/7] Tighten PCI security, expose dev location in sysfs Rajat Jain
2020-06-30  4:49 ` [PATCH v2 1/7] PCI: Keep the ACS capability offset in device Rajat Jain
2020-07-06 15:58   ` Bjorn Helgaas
2020-07-06 22:16     ` Rajat Jain
2020-07-06 23:18       ` Bjorn Helgaas
2020-06-30  4:49 ` [PATCH v2 2/7] PCI: Set "untrusted" flag for truly external devices only Rajat Jain
2020-06-30  7:38   ` Lu Baolu
2020-06-30  7:55   ` Greg Kroah-Hartman
2020-07-06 16:41     ` Bjorn Helgaas
2020-07-06 18:48       ` Greg Kroah-Hartman
2020-07-06 16:38   ` Bjorn Helgaas
2020-07-06 22:31     ` Rajat Jain
2020-07-06 23:30       ` Bjorn Helgaas
2020-07-06 23:40         ` Rajat Jain [this message]
2020-06-30  4:49 ` [PATCH v2 3/7] PCI/ACS: Enable PCI_ACS_TB for untrusted/external-facing devices Rajat Jain
2020-07-06 16:45   ` Bjorn Helgaas
2020-07-06 23:12     ` Rajat Jain
2020-07-06 17:07   ` Bjorn Helgaas
2020-07-06 23:19     ` Rajat Jain
2020-06-30  4:49 ` [PATCH v2 4/7] PCI: Add device even if driver attach failed Rajat Jain
2020-06-30  8:02   ` Greg Kroah-Hartman
2020-07-06 23:35     ` Rajat Jain
2020-06-30  4:49 ` [PATCH v2 5/7] driver core: Add device location to "struct device" and expose it in sysfs Rajat Jain
2020-06-30  8:01   ` Greg Kroah-Hartman
2020-06-30 10:49   ` Heikki Krogerus
2020-06-30 12:52     ` Greg Kroah-Hartman
2020-06-30 13:00       ` Rafael J. Wysocki
2020-06-30 15:38         ` Greg Kroah-Hartman
2020-06-30 16:08           ` Rafael J. Wysocki
2020-06-30 17:00             ` Greg Kroah-Hartman
2020-07-01 18:06               ` Rajat Jain
2020-07-02  5:23                 ` Oliver O'Halloran
2020-07-02  7:32                   ` Greg Kroah-Hartman
2020-07-02  8:40                     ` Oliver O'Halloran
2020-07-02  8:52                       ` Greg Kroah-Hartman
2020-07-02  8:53                         ` Greg Kroah-Hartman
2020-07-07  6:03                   ` Rajat Jain
2020-06-30 17:43   ` Saravana Kannan
2020-06-30  4:49 ` [PATCH v2 6/7] PCI: Move pci_dev->untrusted logic to use device location instead Rajat Jain
2020-06-30  7:39   ` Lu Baolu
2020-06-30  4:49 ` [PATCH v2 7/7] PCI: Add parameter to disable attaching external devices Rajat Jain
2020-07-04 11:44 ` [PATCH v2 0/7] Tighten PCI security, expose dev location in sysfs Pavel Machek
2020-07-06 22:18   ` Rajat Jain

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