iommu/vt-d: Use pci_real_dma_dev() for mapping

The PCI device may have a DMA requester on another bus, such as VMD
subdevices needing to use the VMD endpoint.  This case requires the real
DMA device for the IOMMU mapping, so use pci_real_dma_dev() to find that
device.

Link: https://lore.kernel.org/r/1579613871-301529-5-git-send-email-jonathan.derrick@intel.com
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>

drivers/iommu/intel-iommu.c

@@ -782,6 +782,8 @@ static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devf
 			return NULL;
 #endif
 
+		pdev = pci_real_dma_dev(pdev);
+
 		/* VFs aren't listed in scope tables; we need to look up
 		 * the PF instead to find the IOMMU. */
 		pf_pdev = pci_physfn(pdev);
@@ -2428,6 +2430,9 @@ static struct dmar_domain *find_domain(struct device *dev)
 		     dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO))
 		return NULL;
 
+	if (dev_is_pci(dev))
+		dev = &pci_real_dma_dev(to_pci_dev(dev))->dev;
+
 	/* No lock here, assumes no domain exit in normal case */
 	info = dev->archdata.iommu;
 	if (likely(info))