s390/pci: Ignore RID for isolated VFs

Ensure that VFs used in isolation, that is with their parent PF not
visible to the configuration but with their RID exposed, are treated
compatibly with existing isolated VF use cases without exposed RID
including RoCE Express VFs. This allows creating configurations where
one LPAR manages PFs while their child VFs are used by other LPARs. This
gives the LPAR managing the PFs a role analogous to that of the
hypervisor in a typical use case of passing child VFs to guests.

Instead of creating a multifunction struct zpci_bus whenever a PCI
function with RID exposed is discovered only create such a bus for
configured physical functions and only consider multifunction busses
when searching for an existing bus. Additionally only set zdev->devfn to
the devfn part of the RID once the function is added to a multifunction
bus.

This also fixes probing of more than 7 such isolated VFs from the same
physical bus. This is because common PCI code in pci_scan_slot() only
looks for more functions when pdev->multifunction is set which somewhat
counter intutively is not the case for VFs.

Note that PFs are looked at before their child VFs is guaranteed because
we sort the zpci_list by RID ascending.

Reviewed-by: Gerd Bayer <[e-mail]>
Signed-off-by: Niklas Schnelle <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>

arch/s390/pci/pci_bus.c

···
 	mutex_unlock(&zbus_list_lock);
 }
 
+static bool zpci_bus_is_multifunction_root(struct zpci_dev *zdev)
+{
+	return !s390_pci_no_rid && zdev->rid_available &&
+		zpci_is_device_configured(zdev) &&
+		!zdev->vfn;
+}
+
 /* zpci_bus_create_pci_bus - Create the PCI bus associated with this zbus
  * @zbus: the zbus holding the zdevices
- * @fr: PCI root function that will determine the bus's domain, and bus speeed
+ * @fr: PCI root function that will determine the bus's domain, and bus speed
  * @ops: the pci operations
  *
  * The PCI function @fr determines the domain (its UID), multifunction property
···
 		return domain;
 
 	zbus->domain_nr = domain;
-	zbus->multifunction = fr->rid_available;
+	zbus->multifunction = zpci_bus_is_multifunction_root(fr);
 	zbus->max_bus_speed = fr->max_bus_speed;
 
 	/*
···
 
 	mutex_lock(&zbus_list_lock);
 	list_for_each_entry(zbus, &zbus_list, bus_next) {
+		if (!zbus->multifunction)
+			continue;
 		if (topo_is_tid == zbus->topo_is_tid && topo == zbus->topo) {
 			kref_get(&zbus->kref);
 			goto out_unlock;
···
 {
 	int rc = -EINVAL;
 
+	if (zbus->multifunction) {
+		if (!zdev->rid_available) {
+			WARN_ONCE(1, "rid_available not set for multifunction\n");
+			return rc;
+		}
+		zdev->devfn = zdev->rid & ZPCI_RID_MASK_DEVFN;
+	}
+
 	if (zbus->function[zdev->devfn]) {
 		pr_err("devfn %04x is already assigned\n", zdev->devfn);
 		return rc;
 	}
-
 	zdev->zbus = zbus;
 	zbus->function[zdev->devfn] = zdev;
 	zpci_nb_devices++;
 
-	if (zbus->multifunction && !zdev->rid_available) {
-		WARN_ONCE(1, "rid_available not set for multifunction\n");
-		goto error;
-	}
 	rc = zpci_init_slot(zdev);
 	if (rc)
 		goto error;
···
 		return -ENOSPC;
 	}
 
-	if (zdev->devfn >= ZPCI_FUNCTIONS_PER_BUS)
-		return -EINVAL;
-
 	topo = topo_is_tid ? zdev->tid : zdev->pchid;
-	if (!s390_pci_no_rid && zdev->rid_available)
-		zbus = zpci_bus_get(topo, topo_is_tid);
-
+	zbus = zpci_bus_get(topo, topo_is_tid);
 	if (!zbus) {
 		zbus = zpci_bus_alloc(topo, topo_is_tid);
 		if (!zbus)

arch/s390/pci/pci_clp.c

···
 	zdev->rid_available = response->rid_avail;
 	if (zdev->rid_available)
 		zdev->rid = response->rid;
-	if (!s390_pci_no_rid && zdev->rid_available)
-		zdev->devfn = response->rid & ZPCI_RID_MASK_DEVFN;
 	zdev->tid_avail = response->tid_avail;
 	if (zdev->tid_avail)
 		zdev->tid = response->tid;