Merge branch 'pci/enumeration'

- Split out ARI "next function" handling from the traditional one (Niklas
  Schnelle)

- Move jailhouse "isolated function" (non-zero functions where function 0
  doesn't exist) handling to pci_scan_slot() to avoid duplicating
  multi-function scanning in pci_scan_child_bus_extend() (Niklas Schnelle)

- Extend "isolated function" probing to s390 (Niklas Schnelle).

- Allow s390 zPCI zbus without a function 0 (Niklas Schnelle)

* pci/enumeration:
  s390/pci: allow zPCI zbus without a function zero
  PCI: Extend isolated function probing to s390
  PCI: Move jailhouse's isolated function handling to pci_scan_slot()
  PCI: Split out next_ari_fn() from next_fn()
  PCI: Clean up pci_scan_slot()

arch/s390/pci/pci_bus.c

@@ -145,9 +145,6 @@ int zpci_bus_scan_bus(struct zpci_bus *zbus)
 	struct zpci_dev *zdev;
 	int devfn, rc, ret = 0;
 
-	if (!zbus->function[0])
-		return 0;
-
 	for (devfn = 0; devfn < ZPCI_FUNCTIONS_PER_BUS; devfn++) {
 		zdev = zbus->function[devfn];
 		if (zdev && zdev->state == ZPCI_FN_STATE_CONFIGURED) {
@@ -184,26 +181,26 @@ void zpci_bus_scan_busses(void)
 
 /* zpci_bus_create_pci_bus - Create the PCI bus associated with this zbus
  * @zbus: the zbus holding the zdevices
- * @f0: function 0 of the bus
+ * @fr: PCI root function that will determine the bus's domain, and bus speeed
  * @ops: the pci operations
  *
- * Function zero is taken as a parameter as this is used to determine the
- * domain, multifunction property and maximum bus speed of the entire bus.
+ * The PCI function @fr determines the domain (its UID), multifunction property
+ * and maximum bus speed of the entire bus.
  *
  * Return: 0 on success, an error code otherwise
  */
-static int zpci_bus_create_pci_bus(struct zpci_bus *zbus, struct zpci_dev *f0, struct pci_ops *ops)
+static int zpci_bus_create_pci_bus(struct zpci_bus *zbus, struct zpci_dev *fr, struct pci_ops *ops)
 {
 	struct pci_bus *bus;
 	int domain;
 
-	domain = zpci_alloc_domain((u16)f0->uid);
+	domain = zpci_alloc_domain((u16)fr->uid);
 	if (domain < 0)
 		return domain;
 
 	zbus->domain_nr = domain;
-	zbus->multifunction = f0->rid_available;
-	zbus->max_bus_speed = f0->max_bus_speed;
+	zbus->multifunction = fr->rid_available;
+	zbus->max_bus_speed = fr->max_bus_speed;
 
 	/*
 	 * Note that the zbus->resources are taken over and zbus->resources
@@ -303,47 +300,6 @@ void pcibios_bus_add_device(struct pci_dev *pdev)
 	}
 }
 
-/* zpci_bus_create_hotplug_slots - Add hotplug slot(s) for device added to bus
- * @zdev: the zPCI device that was newly added
- *
- * Add the hotplug slot(s) for the newly added PCI function. Normally this is
- * simply the slot for the function itself. If however we are adding the
- * function 0 on a zbus, it might be that we already registered functions on
- * that zbus but could not create their hotplug slots yet so add those now too.
- *
- * Return: 0 on success, an error code otherwise
- */
-static int zpci_bus_create_hotplug_slots(struct zpci_dev *zdev)
-{
-	struct zpci_bus *zbus = zdev->zbus;
-	int devfn, rc = 0;
-
-	rc = zpci_init_slot(zdev);
-	if (rc)
-		return rc;
-	zdev->has_hp_slot = 1;
-
-	if (zdev->devfn == 0 && zbus->multifunction) {
-		/* Now that function 0 is there we can finally create the
-		 * hotplug slots for those functions with devfn != 0 that have
-		 * been parked in zbus->function[] waiting for us to be able to
-		 * create the PCI bus.
-		 */
-		for  (devfn = 1; devfn < ZPCI_FUNCTIONS_PER_BUS; devfn++) {
-			zdev = zbus->function[devfn];
-			if (zdev && !zdev->has_hp_slot) {
-				rc = zpci_init_slot(zdev);
-				if (rc)
-					return rc;
-				zdev->has_hp_slot = 1;
-			}
-		}
-
-	}
-
-	return rc;
-}
-
 static int zpci_bus_add_device(struct zpci_bus *zbus, struct zpci_dev *zdev)
 {
 	int rc = -EINVAL;
@@ -352,21 +308,19 @@ static int zpci_bus_add_device(struct zpci_bus *zbus, struct zpci_dev *zdev)
 		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->bus) {
-		if (zbus->multifunction && !zdev->rid_available) {
-			WARN_ONCE(1, "rid_available not set for multifunction\n");
-			goto error;
-		}
-
-		zpci_bus_create_hotplug_slots(zdev);
-	} else {
-		/* Hotplug slot will be created once function 0 appears */
-		zbus->multifunction = 1;
+	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;
+	zdev->has_hp_slot = 1;
 
 	return 0;
 
@@ -400,7 +354,11 @@ int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops)
 			return -ENOMEM;
 	}
 
-	if (zdev->devfn == 0) {
+	if (!zbus->bus) {
+		/* The UID of the first PCI function registered with a zpci_bus
+		 * is used as the domain number for that bus. Currently there
+		 * is exactly one zpci_bus per domain.
+		 */
 		rc = zpci_bus_create_pci_bus(zbus, zdev, ops);
 		if (rc)
 			goto error;

drivers/pci/probe.c

@@ -2579,33 +2579,39 @@ struct pci_dev *pci_scan_single_device(struct pci_bus *bus, int devfn)
 }
 EXPORT_SYMBOL(pci_scan_single_device);
 
-static unsigned int next_fn(struct pci_bus *bus, struct pci_dev *dev,
-			    unsigned int fn)
+static int next_ari_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
 {
 	int pos;
 	u16 cap = 0;
 	unsigned int next_fn;
 
-	if (pci_ari_enabled(bus)) {
-		if (!dev)
-			return 0;
-		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
-		if (!pos)
-			return 0;
+	if (!dev)
+		return -ENODEV;
 
-		pci_read_config_word(dev, pos + PCI_ARI_CAP, &cap);
-		next_fn = PCI_ARI_CAP_NFN(cap);
-		if (next_fn <= fn)
-			return 0;	/* protect against malformed list */
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
+	if (!pos)
+		return -ENODEV;
 
-		return next_fn;
-	}
+	pci_read_config_word(dev, pos + PCI_ARI_CAP, &cap);
+	next_fn = PCI_ARI_CAP_NFN(cap);
+	if (next_fn <= fn)
+		return -ENODEV;	/* protect against malformed list */
 
-	/* dev may be NULL for non-contiguous multifunction devices */
-	if (!dev || dev->multifunction)
-		return (fn + 1) % 8;
+	return next_fn;
+}
 
-	return 0;
+static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
+{
+	if (pci_ari_enabled(bus))
+		return next_ari_fn(bus, dev, fn);
+
+	if (fn >= 7)
+		return -ENODEV;
+	/* only multifunction devices may have more functions */
+	if (dev && !dev->multifunction)
+		return -ENODEV;
+
+	return fn + 1;
 }
 
 static int only_one_child(struct pci_bus *bus)
@@ -2643,26 +2649,30 @@ static int only_one_child(struct pci_bus *bus)
  */
 int pci_scan_slot(struct pci_bus *bus, int devfn)
 {
-	unsigned int fn, nr = 0;
 	struct pci_dev *dev;
+	int fn = 0, nr = 0;
 
 	if (only_one_child(bus) && (devfn > 0))
 		return 0; /* Already scanned the entire slot */
 
-	dev = pci_scan_single_device(bus, devfn);
-	if (!dev)
-		return 0;
-	if (!pci_dev_is_added(dev))
-		nr++;
-
-	for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn)) {
+	do {
 		dev = pci_scan_single_device(bus, devfn + fn);
 		if (dev) {
 			if (!pci_dev_is_added(dev))
 				nr++;
-			dev->multifunction = 1;
+			if (fn > 0)
+				dev->multifunction = 1;
+		} else if (fn == 0) {
+			/*
+			 * Function 0 is required unless we are running on
+			 * a hypervisor that passes through individual PCI
+			 * functions.
+			 */
+			if (!hypervisor_isolated_pci_functions())
+				break;
 		}
-	}
+		fn = next_fn(bus, dev, fn);
+	} while (fn >= 0);
 
 	/* Only one slot has PCIe device */
 	if (bus->self && nr)
@@ -2858,29 +2868,14 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
 {
 	unsigned int used_buses, normal_bridges = 0, hotplug_bridges = 0;
 	unsigned int start = bus->busn_res.start;
-	unsigned int devfn, fn, cmax, max = start;
+	unsigned int devfn, cmax, max = start;
 	struct pci_dev *dev;
-	int nr_devs;
 
 	dev_dbg(&bus->dev, "scanning bus\n");
 
 	/* Go find them, Rover! */
-	for (devfn = 0; devfn < 256; devfn += 8) {
-		nr_devs = pci_scan_slot(bus, devfn);
-
-		/*
-		 * The Jailhouse hypervisor may pass individual functions of a
-		 * multi-function device to a guest without passing function 0.
-		 * Look for them as well.
-		 */
-		if (jailhouse_paravirt() && nr_devs == 0) {
-			for (fn = 1; fn < 8; fn++) {
-				dev = pci_scan_single_device(bus, devfn + fn);
-				if (dev)
-					dev->multifunction = 1;
-			}
-		}
-	}
+	for (devfn = 0; devfn < 256; devfn += 8)
+		pci_scan_slot(bus, devfn);
 
 	/* Reserve buses for SR-IOV capability */
 	used_buses = pci_iov_bus_range(bus);

include/linux/hypervisor.h

@@ -32,4 +32,12 @@ static inline bool jailhouse_paravirt(void)
 
 #endif /* !CONFIG_X86 */
 
+static inline bool hypervisor_isolated_pci_functions(void)
+{
+	if (IS_ENABLED(CONFIG_S390))
+		return true;
+
+	return jailhouse_paravirt();
+}
+
 #endif /* __LINUX_HYPEVISOR_H */