iommu/vt-d: Don't reject Host Bridge due to scope mismatch

On a system with two host bridges(0000:00:00.0,0000:80:00.0), iommu
initialization fails with

    DMAR: Device scope type does not match for 0000:80:00.0

This is because the DMAR table reports this device as having scope 2
(ACPI_DMAR_SCOPE_TYPE_BRIDGE):

but the device has a type 0 PCI header:
80:00.0 Class 0600: Device 8086:2020 (rev 06)
00: 86 80 20 20 47 05 10 00 06 00 00 06 10 00 00 00
10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 86 80 00 00
30: 00 00 00 00 90 00 00 00 00 00 00 00 00 01 00 00

VT-d works perfectly on this system, so there's no reason to bail out
on initialization due to this apparent scope mismatch. Add the class
0x06 ("PCI_BASE_CLASS_BRIDGE") as a heuristic for allowing DMAR
initialization for non-bridge PCI devices listed with scope bridge.
Signed-off-by: jimyan <jimyan@baidu.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/dmar.c

@@ -244,7 +244,7 @@ int dmar_insert_dev_scope(struct dmar_pci_notify_info *info,
 		     info->dev->hdr_type != PCI_HEADER_TYPE_NORMAL) ||
 		    (scope->entry_type == ACPI_DMAR_SCOPE_TYPE_BRIDGE &&
 		     (info->dev->hdr_type == PCI_HEADER_TYPE_NORMAL &&
-		      info->dev->class >> 8 != PCI_CLASS_BRIDGE_OTHER))) {
+		      info->dev->class >> 16 != PCI_BASE_CLASS_BRIDGE))) {
 			pr_warn("Device scope type does not match for %s\n",
 				pci_name(info->dev));
 			return -EINVAL;