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* [PATCH] pci: Rename pci_dev->untrusted to pci_dev->external
@ 2021-04-20  0:30 Rajat Jain
  2021-04-20  6:10 ` Christoph Hellwig
  0 siblings, 1 reply; 3+ messages in thread
From: Rajat Jain @ 2021-04-20  0:30 UTC (permalink / raw)
  To: Joerg Roedel, Will Deacon, David Woodhouse, Lu Baolu,
	Bjorn Helgaas, iommu, linux-kernel, linux-pci, helgaas
  Cc: Rajat Jain, rajatxjain

The current flag name "untrusted" is not correct as it is populated
using the firmware property "external-facing" for the parent ports. In
other words, the firmware only says which ports are external facing, so
the field really identifies the devices as external (vs internal).

Only field renaming. No functional change intended.

Signed-off-by: Rajat Jain <rajatja@google.com>
---
 drivers/iommu/dma-iommu.c   |  2 +-
 drivers/iommu/intel/iommu.c |  2 +-
 drivers/iommu/iommu.c       |  2 +-
 drivers/pci/ats.c           |  2 +-
 drivers/pci/pci.c           |  2 +-
 drivers/pci/probe.c         | 12 ++++++------
 drivers/pci/quirks.c        |  2 +-
 include/linux/pci.h         |  9 +--------
 8 files changed, 13 insertions(+), 20 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index af765c813cc8..14769c213f30 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -313,7 +313,7 @@ static void iommu_dma_flush_iotlb_all(struct iova_domain *iovad)
 
 static bool dev_is_untrusted(struct device *dev)
 {
-	return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
+	return dev_is_pci(dev) && to_pci_dev(dev)->external;
 }
 
 /**
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index ee0932307d64..965cc78e0dde 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5511,7 +5511,7 @@ intel_iommu_domain_get_attr(struct iommu_domain *domain,
  */
 static bool risky_device(struct pci_dev *pdev)
 {
-	if (pdev->untrusted) {
+	if (pdev->external) {
 		pci_info(pdev,
 			 "Skipping IOMMU quirk for dev [%04X:%04X] on untrusted PCI link\n",
 			 pdev->vendor, pdev->device);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d0b0a15dba84..abdedc98f3c0 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1482,7 +1482,7 @@ static int iommu_get_def_domain_type(struct device *dev)
 {
 	const struct iommu_ops *ops = dev->bus->iommu_ops;
 
-	if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted)
+	if (dev_is_pci(dev) && to_pci_dev(dev)->external)
 		return IOMMU_DOMAIN_DMA;
 
 	if (ops->def_domain_type)
diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 0d3719407b8b..0d17fb4a15bf 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -42,7 +42,7 @@ bool pci_ats_supported(struct pci_dev *dev)
 	if (!dev->ats_cap)
 		return false;
 
-	return (dev->untrusted == 0);
+	return (dev->external == 0);
 }
 EXPORT_SYMBOL_GPL(pci_ats_supported);
 
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 16a17215f633..ec98892389d7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -886,7 +886,7 @@ static void pci_std_enable_acs(struct pci_dev *dev)
 	ctrl |= (cap & PCI_ACS_UF);
 
 	/* Enable Translation Blocking for external devices */
-	if (dev->external_facing || dev->untrusted)
+	if (dev->external_facing || dev->external)
 		ctrl |= (cap & PCI_ACS_TB);
 
 	pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 953f15abc850..ae4800e82914 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1562,17 +1562,17 @@ static void set_pcie_thunderbolt(struct pci_dev *dev)
 	}
 }
 
-static void set_pcie_untrusted(struct pci_dev *dev)
+static void set_pcie_external(struct pci_dev *dev)
 {
 	struct pci_dev *parent;
 
 	/*
-	 * If the upstream bridge is untrusted we treat this device
-	 * untrusted as well.
+	 * If the upstream bridge is external we mark this device
+	 * external as well.
 	 */
 	parent = pci_upstream_bridge(dev);
-	if (parent && (parent->untrusted || parent->external_facing))
-		dev->untrusted = true;
+	if (parent && (parent->external || parent->external_facing))
+		dev->external = true;
 }
 
 /**
@@ -1814,7 +1814,7 @@ int pci_setup_device(struct pci_dev *dev)
 	/* Need to have dev->cfg_size ready */
 	set_pcie_thunderbolt(dev);
 
-	set_pcie_untrusted(dev);
+	set_pcie_external(dev);
 
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 653660e3ba9e..1054b7d9ee89 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4942,7 +4942,7 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
 	ctrl |= (cap & PCI_ACS_CR);
 	ctrl |= (cap & PCI_ACS_UF);
 
-	if (dev->external_facing || dev->untrusted)
+	if (dev->external_facing || dev->external)
 		ctrl |= (cap & PCI_ACS_TB);
 
 	pci_write_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, ctrl);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 86c799c97b77..a535e2c2b690 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -431,14 +431,7 @@ struct pci_dev {
 	unsigned int	is_hotplug_bridge:1;
 	unsigned int	shpc_managed:1;		/* SHPC owned by shpchp */
 	unsigned int	is_thunderbolt:1;	/* Thunderbolt controller */
-	/*
-	 * Devices marked being untrusted are the ones that can potentially
-	 * execute DMA attacks and similar. They are typically connected
-	 * through external ports such as Thunderbolt but not limited to
-	 * that. When an IOMMU is enabled they should be getting full
-	 * mappings to make sure they cannot access arbitrary memory.
-	 */
-	unsigned int	untrusted:1;
+	unsigned int	external:1;             /* Device sits on an external PCI bus */
 	/*
 	 * Info from the platform, e.g., ACPI or device tree, may mark a
 	 * device as "external-facing".  An external-facing device is
-- 
2.31.1.368.gbe11c130af-goog


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH] pci: Rename pci_dev->untrusted to pci_dev->external
  2021-04-20  0:30 [PATCH] pci: Rename pci_dev->untrusted to pci_dev->external Rajat Jain
@ 2021-04-20  6:10 ` Christoph Hellwig
  2021-04-20 17:07   ` Bjorn Helgaas
  0 siblings, 1 reply; 3+ messages in thread
From: Christoph Hellwig @ 2021-04-20  6:10 UTC (permalink / raw)
  To: Rajat Jain
  Cc: Joerg Roedel, Will Deacon, David Woodhouse, Lu Baolu,
	Bjorn Helgaas, iommu, linux-kernel, linux-pci, helgaas,
	rajatxjain

On Mon, Apr 19, 2021 at 05:30:49PM -0700, Rajat Jain wrote:
> The current flag name "untrusted" is not correct as it is populated
> using the firmware property "external-facing" for the parent ports. In
> other words, the firmware only says which ports are external facing, so
> the field really identifies the devices as external (vs internal).
> 
> Only field renaming. No functional change intended.

I don't think this is a good idea.  First the field should have been
added to the generic struct device as requested multiple times before.
Right now this requires horrible hacks in the IOMMU code to get at the
pci_dev, and also doesn't scale to various other potential users.

Second the untrusted is objectively a better name.  Because untrusted
is how we treat the device, which is what mattes.  External is just
how we come to that conclusion.

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] pci: Rename pci_dev->untrusted to pci_dev->external
  2021-04-20  6:10 ` Christoph Hellwig
@ 2021-04-20 17:07   ` Bjorn Helgaas
  0 siblings, 0 replies; 3+ messages in thread
From: Bjorn Helgaas @ 2021-04-20 17:07 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Rajat Jain, Joerg Roedel, Will Deacon, David Woodhouse, Lu Baolu,
	Bjorn Helgaas, iommu, linux-kernel, linux-pci, rajatxjain

On Tue, Apr 20, 2021 at 07:10:06AM +0100, Christoph Hellwig wrote:
> On Mon, Apr 19, 2021 at 05:30:49PM -0700, Rajat Jain wrote:
> > The current flag name "untrusted" is not correct as it is populated
> > using the firmware property "external-facing" for the parent ports. In
> > other words, the firmware only says which ports are external facing, so
> > the field really identifies the devices as external (vs internal).
> > 
> > Only field renaming. No functional change intended.
> 
> I don't think this is a good idea.  First the field should have been
> added to the generic struct device as requested multiple times before.

Fair point.  There isn't anything PCI-specific about this idea.  The
ACPI "ExternalFacingPort" and DT "external-facing" are currently only
defined for PCI devices, but could be applied elsewhere.

> Right now this requires horrible hacks in the IOMMU code to get at the
> pci_dev, and also doesn't scale to various other potential users.

Agreed, this is definitely suboptimal.  Do you have other users in
mind?  Maybe they could help inform the plan.

> Second the untrusted is objectively a better name.  Because untrusted
> is how we treat the device, which is what mattes.  External is just
> how we come to that conclusion.

The decision to treat "external" as being "untrusted" is a little bit
of policy that the PCI core really doesn't care about, so I think it
does make some sense to let the places that *do* care decide what to
trust based on "external" and possibly other factors, e.g., whether
the device is a BMC or processes untrusted data, etc.

But I guess it makes sense to wait until we have a better motivation
before renaming it, since we don't gain any functionality here.

Bjorn

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-04-20 17:07 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-04-20  0:30 [PATCH] pci: Rename pci_dev->untrusted to pci_dev->external Rajat Jain
2021-04-20  6:10 ` Christoph Hellwig
2021-04-20 17:07   ` Bjorn Helgaas

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