Merge branch 'pci/thunderbolt'

- Detect some Thunderbolt chips that are built-in and hence 'trustworthy'
  by a heuristic since the 'ExternalFacingPort' and 'usb4-host-interface'
  ACPI properties are not quite enough (Esther Shimanovich)

* pci/thunderbolt:
  PCI: Detect and trust built-in Thunderbolt chips

3 files changed, 148 insertions, 7 deletions

diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index 55c4b07ec1f6..0c316bae1726 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -250,6 +250,125 @@ void __init pci_acpi_crs_quirks(void)
 		pr_info("Please notify linux-pci@vger.kernel.org so future kernels can do this automatically\n");
 }
 
+/*
+ * Check if pdev is part of a PCIe switch that is directly below the
+ * specified bridge.
+ */
+static bool pcie_switch_directly_under(struct pci_dev *bridge,
+				       struct pci_dev *pdev)
+{
+	struct pci_dev *parent = pci_upstream_bridge(pdev);
+
+	/* If the device doesn't have a parent, it's not under anything */
+	if (!parent)
+		return false;
+
+	/*
+	 * If the device has a PCIe type, check if it is below the
+	 * corresponding PCIe switch components (if applicable). Then check
+	 * if its upstream port is directly beneath the specified bridge.
+	 */
+	switch (pci_pcie_type(pdev)) {
+	case PCI_EXP_TYPE_UPSTREAM:
+		return parent == bridge;
+
+	case PCI_EXP_TYPE_DOWNSTREAM:
+		if (pci_pcie_type(parent) != PCI_EXP_TYPE_UPSTREAM)
+			return false;
+		parent = pci_upstream_bridge(parent);
+		return parent == bridge;
+
+	case PCI_EXP_TYPE_ENDPOINT:
+		if (pci_pcie_type(parent) != PCI_EXP_TYPE_DOWNSTREAM)
+			return false;
+		parent = pci_upstream_bridge(parent);
+		if (!parent || pci_pcie_type(parent) != PCI_EXP_TYPE_UPSTREAM)
+			return false;
+		parent = pci_upstream_bridge(parent);
+		return parent == bridge;
+	}
+
+	return false;
+}
+
+static bool pcie_has_usb4_host_interface(struct pci_dev *pdev)
+{
+	struct fwnode_handle *fwnode;
+
+	/*
+	 * For USB4, the tunneled PCIe Root or Downstream Ports are marked
+	 * with the "usb4-host-interface" ACPI property, so we look for
+	 * that first. This should cover most cases.
+	 */
+	fwnode = fwnode_find_reference(dev_fwnode(&pdev->dev),
+				       "usb4-host-interface", 0);
+	if (!IS_ERR(fwnode)) {
+		fwnode_handle_put(fwnode);
+		return true;
+	}
+
+	/*
+	 * Any integrated Thunderbolt 3/4 PCIe Root Ports from Intel
+	 * before Alder Lake do not have the "usb4-host-interface"
+	 * property so we use their PCI IDs instead. All these are
+	 * tunneled. This list is not expected to grow.
+	 */
+	if (pdev->vendor == PCI_VENDOR_ID_INTEL) {
+		switch (pdev->device) {
+		/* Ice Lake Thunderbolt 3 PCIe Root Ports */
+		case 0x8a1d:
+		case 0x8a1f:
+		case 0x8a21:
+		case 0x8a23:
+		/* Tiger Lake-LP Thunderbolt 4 PCIe Root Ports */
+		case 0x9a23:
+		case 0x9a25:
+		case 0x9a27:
+		case 0x9a29:
+		/* Tiger Lake-H Thunderbolt 4 PCIe Root Ports */
+		case 0x9a2b:
+		case 0x9a2d:
+		case 0x9a2f:
+		case 0x9a31:
+			return true;
+		}
+	}
+
+	return false;
+}
+
+bool arch_pci_dev_is_removable(struct pci_dev *pdev)
+{
+	struct pci_dev *parent, *root;
+
+	/* pdev without a parent or Root Port is never tunneled */
+	parent = pci_upstream_bridge(pdev);
+	if (!parent)
+		return false;
+	root = pcie_find_root_port(pdev);
+	if (!root)
+		return false;
+
+	/* Internal PCIe devices are not tunneled */
+	if (!root->external_facing)
+		return false;
+
+	/* Anything directly behind a "usb4-host-interface" is tunneled */
+	if (pcie_has_usb4_host_interface(parent))
+		return true;
+
+	/*
+	 * Check if this is a discrete Thunderbolt/USB4 controller that is
+	 * directly behind the non-USB4 PCIe Root Port marked as
+	 * "ExternalFacingPort". Those are not behind a PCIe tunnel.
+	 */
+	if (pcie_switch_directly_under(root, pdev))
+		return false;
+
+	/* PCIe devices after the discrete chip are tunneled */
+	return true;
+}
+
 #ifdef	CONFIG_PCI_MMCONFIG
 static int check_segment(u16 seg, struct device *dev, char *estr)
 {
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 9b2aa4ef3192..8a7e58e20839 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1635,23 +1635,33 @@ static void set_pcie_thunderbolt(struct pci_dev *dev)
 
 static void set_pcie_untrusted(struct pci_dev *dev)
 {
-	struct pci_dev *parent;
+	struct pci_dev *parent = pci_upstream_bridge(dev);
 
+	if (!parent)
+		return;
 	/*
-	 * If the upstream bridge is untrusted we treat this device
+	 * If the upstream bridge is untrusted we treat this device as
 	 * untrusted as well.
 	 */
-	parent = pci_upstream_bridge(dev);
-	if (parent && (parent->untrusted || parent->external_facing))
+	if (parent->untrusted) {
+		dev->untrusted = true;
+		return;
+	}
+
+	if (arch_pci_dev_is_removable(dev)) {
+		pci_dbg(dev, "marking as untrusted\n");
 		dev->untrusted = true;
+	}
 }
 
 static void pci_set_removable(struct pci_dev *dev)
 {
 	struct pci_dev *parent = pci_upstream_bridge(dev);
 
+	if (!parent)
+		return;
 	/*
-	 * We (only) consider everything downstream from an external_facing
+	 * We (only) consider everything tunneled below an external_facing
 	 * device to be removable by the user. We're mainly concerned with
 	 * consumer platforms with user accessible thunderbolt ports that are
 	 * vulnerable to DMA attacks, and we expect those ports to be marked by
@@ -1661,9 +1671,15 @@ static void pci_set_removable(struct pci_dev *dev)
 	 * accessible to user / may not be removed by end user, and thus not
 	 * exposed as "removable" to userspace.
 	 */
-	if (parent &&
-	    (parent->external_facing || dev_is_removable(&parent->dev)))
+	if (dev_is_removable(&parent->dev)) {
+		dev_set_removable(&dev->dev, DEVICE_REMOVABLE);
+		return;
+	}
+
+	if (arch_pci_dev_is_removable(dev)) {
+		pci_dbg(dev, "marking as removable\n");
 		dev_set_removable(&dev->dev, DEVICE_REMOVABLE);
+	}
 }
 
 /**
diff --git a/include/linux/pci.h b/include/linux/pci.h
index e41032dd12a5..5db9b0b2dca1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2606,6 +2606,12 @@ pci_host_bridge_acpi_msi_domain(struct pci_bus *bus) { return NULL; }
 static inline bool pci_pr3_present(struct pci_dev *pdev) { return false; }
 #endif
 
+#if defined(CONFIG_X86) && defined(CONFIG_ACPI)
+bool arch_pci_dev_is_removable(struct pci_dev *pdev);
+#else
+static inline bool arch_pci_dev_is_removable(struct pci_dev *pdev) { return false; }
+#endif
+
 #ifdef CONFIG_EEH
 static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
 {