BACKPORT: FROMLIST: PCI: Rename pci_dev->untrusted to pci_dev->requires_dma_protection

Rename the field to make it more clear, that the device can execute DMA
attacks on the system, and thus the system may need protection from
such attacks from this device.

No functional change intended.

Link: https://lore.kernel.org/all/20250221000943.973221-3-jperaza@google.com/
Bug: 369726566
Change-Id: I87a361b4dbfa889b010e52ed354c356623143b9e
Signed-off-by: Rajat Jain <rajatja@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Joshua Peraza <jperaza@google.com>

drivers/iommu/amd/iommu.c

@@ -2767,8 +2767,7 @@ static int amd_iommu_def_domain_type(struct device *dev)
 	if (!dev_data)
 		return 0;
 
-	/* Always use DMA domain for untrusted device */
+	if (dev_is_pci(dev) && to_pci_dev(dev)->requires_dma_protection)
-	if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted)
 		return IOMMU_DOMAIN_DMA;
 
 	/*

drivers/iommu/dma-iommu.c

@@ -599,16 +599,16 @@ static int iova_reserve_iommu_regions(struct device *dev,
 	return ret;
 }
 
-static bool dev_is_untrusted(struct device *dev)
+static bool dev_requires_dma_protection(struct device *dev)
 {
-	return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
+	return dev_is_pci(dev) && to_pci_dev(dev)->requires_dma_protection;
 }
 
 static bool dev_use_swiotlb(struct device *dev, size_t size,
 			    enum dma_data_direction dir)
 {
 	return IS_ENABLED(CONFIG_SWIOTLB) &&
-		(dev_is_untrusted(dev) ||
+		(dev_requires_dma_protection(dev) ||
 		 dma_kmalloc_needs_bounce(dev, size, dir));
 }
 
@@ -621,7 +621,7 @@ static bool dev_use_sg_swiotlb(struct device *dev, struct scatterlist *sg,
 	if (!IS_ENABLED(CONFIG_SWIOTLB))
 		return false;
 
-	if (dev_is_untrusted(dev))
+	if (dev_requires_dma_protection(dev))
 		return true;
 
 	/*
@@ -1202,12 +1202,12 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 			return DMA_MAPPING_ERROR;
 
 		/*
-		 * Untrusted devices should not see padding areas with random
+		 * Zero the pre- and post-padding to prevent exposing kernel data to devices
-		 * leftover kernel data, so zero the pre- and post-padding.
+		 * requiring DMA protection.
 		 * swiotlb_tbl_map_single() has initialized the bounce buffer
 		 * proper to the contents of the original memory buffer.
 		 */
-		if (dev_is_untrusted(dev)) {
+		if (dev_requires_dma_protection(dev)) {
 			size_t start, virt = (size_t)phys_to_virt(phys);
 
 			/* Pre-padding */
@@ -1748,7 +1748,7 @@ size_t iommu_dma_opt_mapping_size(void)
 
 size_t iommu_dma_max_mapping_size(struct device *dev)
 {
-	if (dev_is_untrusted(dev))
+	if (dev_requires_dma_protection(dev))
 		return swiotlb_max_mapping_size(dev);
 
 	return SIZE_MAX;

drivers/iommu/intel/iommu.c

@@ -3146,7 +3146,7 @@ static int __init platform_optin_force_iommu(void)
 
 	/*
 	 * If Intel-IOMMU is disabled by default, we will apply identity
-	 * map for all devices except those marked as being untrusted.
+	 * map for all devices except those marked as requiring DMA protection.
 	 */
 	if (dmar_disabled)
 		iommu_set_default_passthrough(false);
@@ -4242,13 +4242,13 @@ static bool intel_iommu_is_attach_deferred(struct device *dev)
 }
 
 /*
- * Check that the device does not live on an external facing PCI port that is
+ * Check that the device does not require DMA protection. Such devices should
- * marked as untrusted. Such devices should not be able to apply quirks and
+ * not be able to apply quirks and thus not be able to bypass the IOMMU
- * thus not be able to bypass the IOMMU restrictions.
+ * restrictions.
  */
 static bool risky_device(struct pci_dev *pdev)
 {
-	if (pdev->untrusted) {
+	if (pdev->requires_dma_protection) {
 		pci_info(pdev,
 			 "Skipping IOMMU quirk for dev [%04X:%04X] on untrusted PCI link\n",
 			 pdev->vendor, pdev->device);

drivers/iommu/iommu.c

@@ -1745,10 +1745,9 @@ static int iommu_get_default_domain_type(struct iommu_group *group,
 		driver_type = iommu_get_def_domain_type(group, gdev->dev,
 							driver_type);
 
-		if (dev_is_pci(gdev->dev) && to_pci_dev(gdev->dev)->untrusted) {
+		if (dev_is_pci(gdev->dev) && to_pci_dev(gdev->dev)->requires_dma_protection) {
 			/*
-			 * No ARM32 using systems will set untrusted, it cannot
+			 * ARM32 systems don't support DMA protection.
-			 * work.
 			 */
 			if (WARN_ON(IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)))
 				return -1;

drivers/pci/ats.c

@@ -43,7 +43,7 @@ bool pci_ats_supported(struct pci_dev *dev)
 	if (!dev->ats_cap)
 		return false;
 
-	return (dev->untrusted == 0);
+	return (dev->requires_dma_protection == 0);
 }
 EXPORT_SYMBOL_GPL(pci_ats_supported);
 

drivers/pci/pci-acpi.c

@@ -1465,7 +1465,7 @@ void pci_acpi_setup(struct device *dev, struct acpi_device *adev)
 
 	pci_acpi_optimize_delay(pci_dev, adev->handle);
 	pci_acpi_set_external_facing(pci_dev);
-	pci_dev->untrusted |= pci_dev_has_dma_property(pci_dev);
+	pci_dev->requires_dma_protection |= pci_dev_has_dma_property(pci_dev);
 	pci_acpi_add_edr_notifier(pci_dev);
 
 	pci_acpi_add_pm_notifier(adev, pci_dev);

drivers/pci/pci.c

@@ -1056,7 +1056,7 @@ static void pci_std_enable_acs(struct pci_dev *dev, struct pci_acs *caps)
 	caps->ctrl |= (caps->cap & PCI_ACS_UF);
 
 	/* Enable Translation Blocking for external devices and noats */
-	if (pci_ats_disabled() || dev->external_facing || dev->untrusted)
+	if (pci_ats_disabled() || dev->external_facing || dev->requires_dma_protection)
 		caps->ctrl |= (caps->cap & PCI_ACS_TB);
 }
 

drivers/pci/probe.c

@@ -1631,7 +1631,7 @@ static void set_pcie_thunderbolt(struct pci_dev *dev)
 		dev->is_thunderbolt = 1;
 }
 
-static void set_pcie_untrusted(struct pci_dev *dev)
+static void pci_set_requires_dma_protection(struct pci_dev *dev)
 {
 	struct pci_dev *parent = pci_upstream_bridge(dev);
 
@@ -1641,14 +1641,14 @@ static void set_pcie_untrusted(struct pci_dev *dev)
 	 * If the upstream bridge is untrusted we treat this device as
 	 * untrusted as well.
 	 */
-	if (parent->untrusted) {
+	if (parent->requires_dma_protection) {
-		dev->untrusted = true;
+		dev->requires_dma_protection = true;
 		return;
 	}
 
 	if (arch_pci_dev_is_removable(dev)) {
 		pci_dbg(dev, "marking as untrusted\n");
-		dev->untrusted = true;
+		dev->requires_dma_protection = true;
 	}
 }
 
@@ -1961,7 +1961,7 @@ int pci_setup_device(struct pci_dev *dev)
 	/* Need to have dev->cfg_size ready */
 	set_pcie_thunderbolt(dev);
 
-	set_pcie_untrusted(dev);
+	pci_set_requires_dma_protection(dev);
 
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;

drivers/pci/quirks.c

@@ -5299,7 +5299,7 @@ static void pci_quirk_enable_intel_rp_mpc_acs(struct pci_dev *dev)
  * PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF
  *
  * TODO: This quirk also needs to do equivalent of PCI_ACS_TB,
- * if dev->external_facing || dev->untrusted
+ * if dev->external_facing || dev->requires_dma_protection
  */
 static int pci_quirk_enable_intel_pch_acs(struct pci_dev *dev)
 {
@@ -5340,7 +5340,7 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
 	ctrl |= (cap & PCI_ACS_CR);
 	ctrl |= (cap & PCI_ACS_UF);
 
-	if (pci_ats_disabled() || dev->external_facing || dev->untrusted)
+	if (pci_ats_disabled() || dev->external_facing || dev->requires_dma_protection)
 		ctrl |= (cap & PCI_ACS_TB);
 
 	pci_write_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, ctrl);

include/linux/pci.h

@@ -444,13 +444,14 @@ struct pci_dev {
 	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
+	 * Devices marked with requires_dma_protection are the ones that can
-	 * execute DMA attacks and similar. They are typically connected
+	 * 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	requires_dma_protection:1;
+
 	/*
 	 * Info from the platform, e.g., ACPI or device tree, may mark a
 	 * device as "external-facing".  An external-facing device is