Merge branch 'pci/reset'

- Update slot handling so all ARI functions are treated as being in the
  same slot.  They're all reset by Secondary Bus Reset, but previously
  drivers of ARI functions that appeared to be on a non-zero device weren't
  notified and fatal hardware errors could result (Keith Busch)

- Make sysfs reset_subordinate hotplug safe to avoid spurious hotplug
  events (Keith Busch)

- Consolidate bus iteration across the _lock(), _unlock(), and _trylock()
  functions for pci_bus and pci_slot (Ilpo Järvinen)

- Hide Secondary Bus Reset ('bus') from sysfs reset_methods if masked by
  CXL because it has no effect (Vidya Sagar)

* pci/reset:
  PCI/CXL: Hide SBR from reset_methods if masked by CXL
  PCI: Consolidate pci_bus/slot_lock/unlock/trylock()
  PCI: Make reset_subordinate hotplug safe
  PCI: Allow all bus devices to use the same slot
  PCI: Rename __pci_bus_reset() and __pci_slot_reset()

6 files changed, 153 insertions, 114 deletions

diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
index 1e9158d7bac7..2cafd3b26f34 100644
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -79,7 +79,8 @@ static int init_slot(struct controller *ctrl)
 	snprintf(name, SLOT_NAME_SIZE, "%u", PSN(ctrl));
 
 	retval = pci_hp_initialize(&ctrl->hotplug_slot,
-				   ctrl->pcie->port->subordinate, 0, name);
+				   ctrl->pcie->port->subordinate,
+				   PCI_SLOT_ALL_DEVICES, name);
 	if (retval) {
 		ctrl_err(ctrl, "pci_hp_initialize failed: error %d\n", retval);
 		kfree(ops);
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 16eaaf749ba9..a2f8a5d6190f 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -553,7 +553,6 @@ static ssize_t reset_subordinate_store(struct device *dev,
 				const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	struct pci_bus *bus = pdev->subordinate;
 	unsigned long val;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -563,7 +562,7 @@ static ssize_t reset_subordinate_store(struct device *dev,
 		return -EINVAL;
 
 	if (val) {
-		int ret = __pci_reset_bus(bus);
+		int ret = pci_try_reset_bridge(pdev);
 
 		if (ret)
 			return ret;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b53488987f2c..09807a65ef87 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4911,12 +4911,8 @@ static int pci_reset_bus_function(struct pci_dev *dev, bool probe)
 	 * If "dev" is below a CXL port that has SBR control masked, SBR
 	 * won't do anything, so return error.
 	 */
-	if (bridge && cxl_sbr_masked(bridge)) {
-		if (probe)
-			return 0;
-
+	if (bridge && pcie_is_cxl(bridge) && cxl_sbr_masked(bridge))
 		return -ENOTTY;
-	}
 
 	rc = pci_dev_reset_iommu_prepare(dev);
 	if (rc) {
@@ -5289,13 +5285,21 @@ static bool pci_bus_resettable(struct pci_bus *bus)
 	return true;
 }
 
+static void pci_bus_lock(struct pci_bus *bus);
+static void pci_bus_unlock(struct pci_bus *bus);
+static int pci_bus_trylock(struct pci_bus *bus);
+
 /* Lock devices from the top of the tree down */
-static void pci_bus_lock(struct pci_bus *bus)
+static void __pci_bus_lock(struct pci_bus *bus, struct pci_slot *slot)
 {
-	struct pci_dev *dev;
+	struct pci_dev *dev, *bridge = bus->self;
+
+	if (bridge)
+		pci_dev_lock(bridge);
 
-	pci_dev_lock(bus->self);
 	list_for_each_entry(dev, &bus->devices, bus_list) {
+		if (slot && (!dev->slot || dev->slot != slot))
+			continue;
 		if (dev->subordinate)
 			pci_bus_lock(dev->subordinate);
 		else
@@ -5304,28 +5308,34 @@ static void pci_bus_lock(struct pci_bus *bus)
 }
 
 /* Unlock devices from the bottom of the tree up */
-static void pci_bus_unlock(struct pci_bus *bus)
+static void __pci_bus_unlock(struct pci_bus *bus, struct pci_slot *slot)
 {
-	struct pci_dev *dev;
+	struct pci_dev *dev, *bridge = bus->self;
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
+		if (slot && (!dev->slot || dev->slot != slot))
+			continue;
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
 		else
 			pci_dev_unlock(dev);
 	}
-	pci_dev_unlock(bus->self);
+
+	if (bridge)
+		pci_dev_unlock(bridge);
 }
 
 /* Return 1 on successful lock, 0 on contention */
-static int pci_bus_trylock(struct pci_bus *bus)
+static int __pci_bus_trylock(struct pci_bus *bus, struct pci_slot *slot)
 {
-	struct pci_dev *dev;
+	struct pci_dev *dev, *bridge = bus->self;
 
-	if (!pci_dev_trylock(bus->self))
+	if (bridge && !pci_dev_trylock(bridge))
 		return 0;
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
+		if (slot && (!dev->slot || dev->slot != slot))
+			continue;
 		if (dev->subordinate) {
 			if (!pci_bus_trylock(dev->subordinate))
 				goto unlock;
@@ -5336,15 +5346,37 @@ static int pci_bus_trylock(struct pci_bus *bus)
 
 unlock:
 	list_for_each_entry_continue_reverse(dev, &bus->devices, bus_list) {
+		if (slot && (!dev->slot || dev->slot != slot))
+			continue;
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
 		else
 			pci_dev_unlock(dev);
 	}
-	pci_dev_unlock(bus->self);
+
+	if (bridge)
+		pci_dev_unlock(bridge);
 	return 0;
 }
 
+/* Lock devices from the top of the tree down */
+static void pci_bus_lock(struct pci_bus *bus)
+{
+	__pci_bus_lock(bus, NULL);
+}
+
+/* Unlock devices from the bottom of the tree up */
+static void pci_bus_unlock(struct pci_bus *bus)
+{
+	__pci_bus_unlock(bus, NULL);
+}
+
+/* Return 1 on successful lock, 0 on contention */
+static int pci_bus_trylock(struct pci_bus *bus)
+{
+	return __pci_bus_trylock(bus, NULL);
+}
+
 /* Do any devices on or below this slot prevent a bus reset? */
 static bool pci_slot_resettable(struct pci_slot *slot)
 {
@@ -5367,72 +5399,19 @@ static bool pci_slot_resettable(struct pci_slot *slot)
 /* Lock devices from the top of the tree down */
 static void pci_slot_lock(struct pci_slot *slot)
 {
-	struct pci_dev *dev, *bridge = slot->bus->self;
-
-	if (bridge)
-		pci_dev_lock(bridge);
-
-	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
-		if (!dev->slot || dev->slot != slot)
-			continue;
-		if (dev->subordinate)
-			pci_bus_lock(dev->subordinate);
-		else
-			pci_dev_lock(dev);
-	}
+	__pci_bus_lock(slot->bus, slot);
 }
 
 /* Unlock devices from the bottom of the tree up */
 static void pci_slot_unlock(struct pci_slot *slot)
 {
-	struct pci_dev *dev, *bridge = slot->bus->self;
-
-	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
-		if (!dev->slot || dev->slot != slot)
-			continue;
-		if (dev->subordinate)
-			pci_bus_unlock(dev->subordinate);
-		else
-			pci_dev_unlock(dev);
-	}
-
-	if (bridge)
-		pci_dev_unlock(bridge);
+	__pci_bus_unlock(slot->bus, slot);
 }
 
 /* Return 1 on successful lock, 0 on contention */
 static int pci_slot_trylock(struct pci_slot *slot)
 {
-	struct pci_dev *dev, *bridge = slot->bus->self;
-
-	if (bridge && !pci_dev_trylock(bridge))
-		return 0;
-
-	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
-		if (!dev->slot || dev->slot != slot)
-			continue;
-		if (dev->subordinate) {
-			if (!pci_bus_trylock(dev->subordinate))
-				goto unlock;
-		} else if (!pci_dev_trylock(dev))
-			goto unlock;
-	}
-	return 1;
-
-unlock:
-	list_for_each_entry_continue_reverse(dev,
-					     &slot->bus->devices, bus_list) {
-		if (!dev->slot || dev->slot != slot)
-			continue;
-		if (dev->subordinate)
-			pci_bus_unlock(dev->subordinate);
-		else
-			pci_dev_unlock(dev);
-	}
-
-	if (bridge)
-		pci_dev_unlock(bridge);
-	return 0;
+	return __pci_bus_trylock(slot->bus, slot);
 }
 
 /*
@@ -5538,7 +5517,7 @@ int pci_probe_reset_slot(struct pci_slot *slot)
 EXPORT_SYMBOL_GPL(pci_probe_reset_slot);
 
 /**
- * __pci_reset_slot - Try to reset a PCI slot
+ * pci_try_reset_slot - Try to reset a PCI slot
  * @slot: PCI slot to reset
  *
  * A PCI bus may host multiple slots, each slot may support a reset mechanism
@@ -5552,7 +5531,7 @@ EXPORT_SYMBOL_GPL(pci_probe_reset_slot);
  *
  * Same as above except return -EAGAIN if the slot cannot be locked
  */
-static int __pci_reset_slot(struct pci_slot *slot)
+static int pci_try_reset_slot(struct pci_slot *slot)
 {
 	int rc;
 
@@ -5594,14 +5573,44 @@ static int pci_bus_reset(struct pci_bus *bus, bool probe)
 }
 
 /**
- * pci_bus_error_reset - reset the bridge's subordinate bus
- * @bridge: The parent device that connects to the bus to reset
+ * pci_try_reset_bus - Try to reset a PCI bus
+ * @bus: top level PCI bus to reset
+ *
+ * Same as above except return -EAGAIN if the bus cannot be locked
+ */
+static int pci_try_reset_bus(struct pci_bus *bus)
+{
+	int rc;
+
+	rc = pci_bus_reset(bus, PCI_RESET_PROBE);
+	if (rc)
+		return rc;
+
+	if (pci_bus_trylock(bus)) {
+		pci_bus_save_and_disable_locked(bus);
+		might_sleep();
+		rc = pci_bridge_secondary_bus_reset(bus->self);
+		pci_bus_restore_locked(bus);
+		pci_bus_unlock(bus);
+	} else
+		rc = -EAGAIN;
+
+	return rc;
+}
+
+#define PCI_RESET_RESTORE true
+#define PCI_RESET_NO_RESTORE false
+/**
+ * pci_reset_bridge - reset a bridge's subordinate bus
+ * @bridge: bridge that connects to the bus to reset
+ * @restore: when true use a reset method that invokes pci_dev_restore() post
+ *           reset for affected devices
  *
  * This function will first try to reset the slots on this bus if the method is
  * available. If slot reset fails or is not available, this will fall back to a
  * secondary bus reset.
  */
-int pci_bus_error_reset(struct pci_dev *bridge)
+static int pci_reset_bridge(struct pci_dev *bridge, bool restore)
 {
 	struct pci_bus *bus = bridge->subordinate;
 	struct pci_slot *slot;
@@ -5617,18 +5626,43 @@ int pci_bus_error_reset(struct pci_dev *bridge)
 		if (pci_probe_reset_slot(slot))
 			goto bus_reset;
 
-	list_for_each_entry(slot, &bus->slots, list)
-		if (pci_slot_reset(slot, PCI_RESET_DO_RESET))
+	list_for_each_entry(slot, &bus->slots, list) {
+		int ret;
+
+		if (restore)
+			ret = pci_try_reset_slot(slot);
+		else
+			ret = pci_slot_reset(slot, PCI_RESET_DO_RESET);
+
+		if (ret)
 			goto bus_reset;
+	}
 
 	mutex_unlock(&pci_slot_mutex);
 	return 0;
 bus_reset:
 	mutex_unlock(&pci_slot_mutex);
+
+	if (restore)
+		return pci_try_reset_bus(bus);
 	return pci_bus_reset(bridge->subordinate, PCI_RESET_DO_RESET);
 }
 
 /**
+ * pci_bus_error_reset - reset the bridge's subordinate bus
+ * @bridge: The parent device that connects to the bus to reset
+ */
+int pci_bus_error_reset(struct pci_dev *bridge)
+{
+	return pci_reset_bridge(bridge, PCI_RESET_NO_RESTORE);
+}
+
+int pci_try_reset_bridge(struct pci_dev *bridge)
+{
+	return pci_reset_bridge(bridge, PCI_RESET_RESTORE);
+}
+
+/**
  * pci_probe_reset_bus - probe whether a PCI bus can be reset
  * @bus: PCI bus to probe
  *
@@ -5641,32 +5675,6 @@ int pci_probe_reset_bus(struct pci_bus *bus)
 EXPORT_SYMBOL_GPL(pci_probe_reset_bus);
 
 /**
- * __pci_reset_bus - Try to reset a PCI bus
- * @bus: top level PCI bus to reset
- *
- * Same as above except return -EAGAIN if the bus cannot be locked
- */
-int __pci_reset_bus(struct pci_bus *bus)
-{
-	int rc;
-
-	rc = pci_bus_reset(bus, PCI_RESET_PROBE);
-	if (rc)
-		return rc;
-
-	if (pci_bus_trylock(bus)) {
-		pci_bus_save_and_disable_locked(bus);
-		might_sleep();
-		rc = pci_bridge_secondary_bus_reset(bus->self);
-		pci_bus_restore_locked(bus);
-		pci_bus_unlock(bus);
-	} else
-		rc = -EAGAIN;
-
-	return rc;
-}
-
-/**
  * pci_reset_bus - Try to reset a PCI bus
  * @pdev: top level PCI device to reset via slot/bus
  *
@@ -5675,7 +5683,7 @@ int __pci_reset_bus(struct pci_bus *bus)
 int pci_reset_bus(struct pci_dev *pdev)
 {
 	return (!pci_probe_reset_slot(pdev->slot)) ?
-	    __pci_reset_slot(pdev->slot) : __pci_reset_bus(pdev->bus);
+	    pci_try_reset_slot(pdev->slot) : pci_try_reset_bus(pdev->bus);
 }
 EXPORT_SYMBOL_GPL(pci_reset_bus);
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 13d998fbacce..a1d2ecb56207 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -231,7 +231,7 @@ bool pci_reset_supported(struct pci_dev *dev);
 void pci_init_reset_methods(struct pci_dev *dev);
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
 int pci_bus_error_reset(struct pci_dev *dev);
-int __pci_reset_bus(struct pci_bus *bus);
+int pci_try_reset_bridge(struct pci_dev *bridge);
 
 struct pci_cap_saved_data {
 	u16		cap_nr;
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 787311614e5b..e0b7fb43423c 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -42,6 +42,15 @@ static ssize_t address_read_file(struct pci_slot *slot, char *buf)
 				  pci_domain_nr(slot->bus),
 				  slot->bus->number);
 
+	/*
+	 * Preserve legacy ABI expectations that hotplug drivers that manage
+	 * multiple devices per slot emit 0 for the device number.
+	 */
+	if (slot->number == PCI_SLOT_ALL_DEVICES)
+		return sysfs_emit(buf, "%04x:%02x:00\n",
+				  pci_domain_nr(slot->bus),
+				  slot->bus->number);
+
 	return sysfs_emit(buf, "%04x:%02x:%02x\n",
 			  pci_domain_nr(slot->bus),
 			  slot->bus->number,
@@ -73,7 +82,8 @@ static void pci_slot_release(struct kobject *kobj)
 
 	down_read(&pci_bus_sem);
 	list_for_each_entry(dev, &slot->bus->devices, bus_list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
+		if (slot->number == PCI_SLOT_ALL_DEVICES ||
+		    PCI_SLOT(dev->devfn) == slot->number)
 			dev->slot = NULL;
 	up_read(&pci_bus_sem);
 
@@ -166,7 +176,8 @@ void pci_dev_assign_slot(struct pci_dev *dev)
 
 	mutex_lock(&pci_slot_mutex);
 	list_for_each_entry(slot, &dev->bus->slots, list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
+		if (slot->number == PCI_SLOT_ALL_DEVICES ||
+		    PCI_SLOT(dev->devfn) == slot->number)
 			dev->slot = slot;
 	mutex_unlock(&pci_slot_mutex);
 }
@@ -188,7 +199,8 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
 /**
  * pci_create_slot - create or increment refcount for physical PCI slot
  * @parent: struct pci_bus of parent bridge
- * @slot_nr: PCI_SLOT(pci_dev->devfn) or -1 for placeholder
+ * @slot_nr: PCI_SLOT(pci_dev->devfn), -1 for placeholder, or
+ *	PCI_SLOT_ALL_DEVICES
  * @name: user visible string presented in /sys/bus/pci/slots/<name>
  * @hotplug: set if caller is hotplug driver, NULL otherwise
  *
@@ -222,6 +234,16 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
  * consist solely of a dddd:bb tuple, where dddd is the PCI domain of the
  * %struct pci_bus and bb is the bus number. In other words, the devfn of
  * the 'placeholder' slot will not be displayed.
+ *
+ * Bus-wide slots:
+ * For PCIe hotplug, the physical slot encompasses the entire secondary
+ * bus, not just a single device number. If the device supports ARI and ARI
+ * Forwarding is enabled in the upstream bridge, a multi-function device
+ * may include functions that appear to have several different device
+ * numbers, i.e., PCI_SLOT() values.  Pass @slot_nr == PCI_SLOT_ALL_DEVICES
+ * to create a slot that matches all devices on the bus. Unlike placeholder
+ * slots, bus-wide slots go through normal slot lookup and reuse existing
+ * slots if present.
  */
 struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
 				 const char *name,
@@ -285,7 +307,8 @@ placeholder:
 
 	down_read(&pci_bus_sem);
 	list_for_each_entry(dev, &parent->devices, bus_list)
-		if (PCI_SLOT(dev->devfn) == slot_nr)
+		if (slot_nr == PCI_SLOT_ALL_DEVICES ||
+		    PCI_SLOT(dev->devfn) == slot_nr)
 			dev->slot = slot;
 	up_read(&pci_bus_sem);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 47c5b0c09ffb..cc98713e3ce8 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -72,12 +72,20 @@
 /* return bus from PCI devid = ((u16)bus_number) << 8) | devfn */
 #define PCI_BUS_NUM(x) (((x) >> 8) & 0xff)
 
+/*
+ * PCI_SLOT_ALL_DEVICES indicates a slot that covers all devices on the bus.
+ * Used for PCIe hotplug where the physical slot is the entire secondary bus,
+ * and, if ARI Forwarding is enabled, functions may appear to be on multiple
+ * devices.
+ */
+#define PCI_SLOT_ALL_DEVICES	0xfe
+
 /* pci_slot represents a physical slot */
 struct pci_slot {
 	struct pci_bus		*bus;		/* Bus this slot is on */
 	struct list_head	list;		/* Node in list of slots */
 	struct hotplug_slot	*hotplug;	/* Hotplug info (move here) */
-	unsigned char		number;		/* PCI_SLOT(pci_dev->devfn) */
+	unsigned char		number;		/* Device nr, or PCI_SLOT_ALL_DEVICES */
 	struct kobject		kobj;
 };