iommu/vt-d: Use Real PCI DMA device for IRTE

VMD retransmits child device MSI-X with the VMD endpoint's requester-id.
In order to support direct interrupt remapping of VMD child devices,
ensure that the IRTE is programmed with the VMD endpoint's requester-id
using pci_real_dma_dev().

Link: https://lore.kernel.org/r/20210210161315.316097-2-jonathan.derrick@intel.com
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Joerg Roedel <jroedel@suse.de>

Author: Jon Derrick

drivers/iommu/intel/irq_remapping.c

@@ -1280,7 +1280,8 @@ static void intel_irq_remapping_prepare_irte(struct intel_ir_data *data,
 		break;
 	case X86_IRQ_ALLOC_TYPE_PCI_MSI:
 	case X86_IRQ_ALLOC_TYPE_PCI_MSIX:
-		set_msi_sid(irte, msi_desc_to_pci_dev(info->desc));
+		set_msi_sid(irte,
+			    pci_real_dma_dev(msi_desc_to_pci_dev(info->desc)));
 		break;
 	default:
 		BUG_ON(1);