commit 06d3104a1d029fe498dcb29fc71ef34c51116bf0
Author: Alex Williamson <alex.williamson@redhat.com>
Date:   Thu Aug 23 14:40:26 2012 -0600

    intel-iommu: Add quirk for known broken devices
    
    Several devices have been found to break pci_find_upstream_pcie_bridge
    because they claim to be conventional PCI-to-PCI bridges, but are
    directly connected to upstream PCIe root ports.  These are probably
    really PCIe-to-PCI bridges, but we don't know for certain and
    therefore don't know how to handle how they tag transactions from
    subordinate devices.  Since we don't know that, disable VT-d support
    when these are found in the system.
    
    Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 2297ec1..6ce9d9f 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4300,3 +4300,51 @@ static void __init check_tylersburg_isoch(void)
 	printk(KERN_WARNING "DMAR: Recommended TLB entries for ISOCH unit is 16; your BIOS set %d\n",
 	       vtisochctrl);
 }
+
+static __devinit void quirk_bad_pcie_bridge(struct pci_dev *dev)
+{
+	struct acpi_table_header *header = NULL;
+	acpi_status status;
+
+	if (no_iommu || dmar_disabled || !iommu_detected)
+		return;
+
+	status = acpi_get_table(ACPI_SIG_DMAR, 0, &header);
+	if (!ACPI_SUCCESS(status))
+		return;
+
+	/*
+	 * If we find a PCI-to-PCI bridge that's not on the root bus and
+	 * connected upstream to a PCIe device that is not a PCIe-to-PCI
+	 * bridge, it's probably actually a PCIe device.  This will make
+	 * pci_find_upstream_pcie_bridge() trigger a warning.  We don't
+	 * really know how to handle tagging on such devices, so we don't
+	 * know how to program the IOMMU.  Disable VT-d on systems with
+	 * this broken hardware.  See:
+	 *
+	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
+	 */
+	if (!pci_is_pcie(dev) && dev->hdr_type == PCI_HEADER_TYPE_BRIDGE &&
+	    !pci_is_root_bus(dev->bus) && pci_is_pcie(dev->bus->self) &&
+	    dev->bus->self->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE) {
+
+		pr_info("Your hardware is broken, device %s claims to be a conventional PCI bridge device connected to an upstream PCIe device that is not a PCIe-to-PCI bridge.  Disabling VT-d support on this system.\n",
+		     pci_name(dev));
+		dmar_disabled = 1;
+
+		if (tboot_enabled())
+			panic("tboot: VT-d cannot be enabled on this system\n");
+	}
+}
+
+/*
+ * The following devices are known to need this quirk:
+ *  - ASMedia Technology Inc. Device 1080 (0x1b21, 0x1080)
+ *  - Tundra Semiconductor Corp. Device 8113 (0x10e3, 0x8113)
+ *  - Integrated Technology Express, Inc. Device 8892 (0x1283, 0x8892)
+ *
+ * We could probably call this on PCI_ANY_ID if we need to.
+ */
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ASMEDIA, 0x1080, quirk_bad_pcie_bridge);
+DECLARE_PCI_FIXUP_HEADER(0x10e3, 0x8113, quirk_bad_pcie_bridge);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ITE, 0x8892, quirk_bad_pcie_bridge);