VFIO updates for v4.19

- Mark switch fall throughs (Gustavo A. R. Silva)
 
  - Disable binding SR-IOV enabled PFs (Alex Williamson)
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Merge tag 'vfio-v4.19-rc1' of git://github.com/awilliam/linux-vfio

Pull VFIO updates from Alex Williamson:

 - mark switch fall-through cases (Gustavo A. R. Silva)

 - disable binding SR-IOV enabled PFs (Alex Williamson)

* tag 'vfio-v4.19-rc1' of git://github.com/awilliam/linux-vfio:
  vfio-pci: Disable binding to PFs with SR-IOV enabled
  vfio: Mark expected switch fall-throughs

drivers/vfio/pci/vfio_pci.c

@@ -789,7 +789,7 @@ static long vfio_pci_ioctl(void *device_data,
 		case VFIO_PCI_ERR_IRQ_INDEX:
 			if (pci_is_pcie(vdev->pdev))
 				break;
-		/* pass thru to return error */
+		/* fall through */
 		default:
 			return -EINVAL;
 		}
@@ -1192,6 +1192,19 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
 		return -EINVAL;
 
+	/*
+	 * Prevent binding to PFs with VFs enabled, this too easily allows
+	 * userspace instance with VFs and PFs from the same device, which
+	 * cannot work.  Disabling SR-IOV here would initiate removing the
+	 * VFs, which would unbind the driver, which is prone to blocking
+	 * if that VF is also in use by vfio-pci.  Just reject these PFs
+	 * and let the user sort it out.
+	 */
+	if (pci_num_vf(pdev)) {
+		pci_warn(pdev, "Cannot bind to PF with SR-IOV enabled\n");
+		return -EBUSY;
+	}
+
 	group = vfio_iommu_group_get(&pdev->dev);
 	if (!group)
 		return -EINVAL;

drivers/vfio/vfio_iommu_type1.c

@@ -1601,6 +1601,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
 		break;
 	case VFIO_TYPE1_NESTING_IOMMU:
 		iommu->nesting = true;
+		/* fall through */
 	case VFIO_TYPE1v2_IOMMU:
 		iommu->v2 = true;
 		break;