intel-iommu: Fix device-to-iommu mapping for PCI-PCI bridges.

When the DMAR table identifies that a PCI-PCI bridge belongs to a given
IOMMU, that means that the bridge and all devices behind it should be
associated with the IOMMU. Not just the bridge itself.

This fixes the device_to_iommu() function accordingly.

(It's broken if you have the same PCI bus numbers in multiple domains,
but this function was always broken in that way; I'll be dealing with
that later).
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/pci/intel-iommu.c

@@ -477,11 +477,16 @@ static struct intel_iommu *device_to_iommu(u8 bus, u8 devfn)
 		if (drhd->ignored)
 			continue;
 
-		for (i = 0; i < drhd->devices_cnt; i++)
+		for (i = 0; i < drhd->devices_cnt; i++) {
 			if (drhd->devices[i] &&
 			    drhd->devices[i]->bus->number == bus &&
 			    drhd->devices[i]->devfn == devfn)
 				return drhd->iommu;
+			if (drhd->devices[i]->subordinate &&
+			    drhd->devices[i]->subordinate->number <= bus &&
+			    drhd->devices[i]->subordinate->subordinate >= bus)
+				return drhd->iommu;
+		}
 
 		if (drhd->include_all)
 			return drhd->iommu;