[PATCH v5 00/23] PCI: Allow BAR movement during hotplug

@@ -1645,7 +1645,7 @@ static int nvme_remap_bar(struct nvme_dev *dev, unsigned long size)
 {
 	struct pci_dev *pdev = to_pci_dev(dev->dev);
 
-	if (size <= dev->bar_mapped_size)
+	if (dev->bar && size <= dev->bar_mapped_size)
 		return 0;
 	if (size > pci_resource_len(pdev, 0))
 		return -ENOMEM;

@@ -2980,6 +2980,23 @@ static void nvme_error_resume(struct pci_dev *pdev)
 	flush_work(&dev->ctrl.reset_work);
 }
 
+static void nvme_rescan_prepare(struct pci_dev *pdev)
+{
+	struct nvme_dev *dev = pci_get_drvdata(pdev);
+
+	nvme_dev_disable(dev, false);
+	nvme_dev_unmap(dev);
+	dev->bar = NULL;
+}
+
+static void nvme_rescan_done(struct pci_dev *pdev)
+{
+	struct nvme_dev *dev = pci_get_drvdata(pdev);
+
+	nvme_dev_map(dev);
+	nvme_reset_ctrl_sync(&dev->ctrl);
+}
+
 static const struct pci_error_handlers nvme_err_handler = {
 	.error_detected	= nvme_error_detected,
 	.slot_reset	= nvme_slot_reset,

@@ -3049,6 +3066,8 @@ static struct pci_driver nvme_driver = {
 #endif
 	.sriov_configure = pci_sriov_configure_simple,
 	.err_handler	= &nvme_err_handler,
+	.rescan_prepare	= nvme_rescan_prepare,
+	.rescan_done	= nvme_rescan_done,
 };
 
 static int __init nvme_init(void)

@@ -1652,6 +1652,14 @@ static void pci_enable_bridge(struct pci_dev *dev)
 		pci_enable_bridge(bridge);
 
 	if (pci_is_enabled(dev)) {
+		int i, bars = 0;
+
+		for (i = PCI_BRIDGE_RESOURCES; i < DEVICE_COUNT_RESOURCE; i++) {
+			if (dev->resource[i].flags & (IORESOURCE_MEM | IORESOURCE_IO))
+				bars |= (1 << i);
+		}
+		do_pci_enable_device(dev, bars);
+
 		if (!dev->is_busmaster)
 			pci_set_master(dev);
 		mutex_unlock(&dev->enable_mutex);

@@ -1645,6 +1645,8 @@ static void pci_enable_bridge(struct pci_dev *dev)
 	struct pci_dev *bridge;
 	int retval;
 
+	mutex_lock(&dev->enable_mutex);
+
 	bridge = pci_upstream_bridge(dev);
 	if (bridge)
 		pci_enable_bridge(bridge);

@@ -1652,6 +1654,7 @@ static void pci_enable_bridge(struct pci_dev *dev)
 	if (pci_is_enabled(dev)) {
 		if (!dev->is_busmaster)
 			pci_set_master(dev);
+		mutex_unlock(&dev->enable_mutex);
 		return;
 	}
 

@@ -1660,11 +1663,14 @@ static void pci_enable_bridge(struct pci_dev *dev)
 		pci_err(dev, "Error enabling bridge (%d), continuing\n",
 			retval);
 	pci_set_master(dev);
+	mutex_unlock(&dev->enable_mutex);
 }
 
 static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
 {
 	struct pci_dev *bridge;
+	/* Enable-locking of bridges is performed within the pci_enable_bridge() */
+	bool need_lock = !dev->subordinate;
 	int err;
 	int i, bars = 0;
 

@@ -1680,8 +1686,13 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
 		dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
 	}
 
-	if (atomic_inc_return(&dev->enable_cnt) > 1)
+	if (need_lock)
+		mutex_lock(&dev->enable_mutex);
+	if (pci_is_enabled(dev)) {
+		if (need_lock)
+			mutex_unlock(&dev->enable_mutex);
 		return 0;		/* already enabled */
+	}
 
 	bridge = pci_upstream_bridge(dev);
 	if (bridge)

@@ -1696,8 +1707,10 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
 			bars |= (1 << i);
 
 	err = do_pci_enable_device(dev, bars);
-	if (err < 0)
-		atomic_dec(&dev->enable_cnt);
+	if (err >= 0)
+		atomic_inc(&dev->enable_cnt);
+	if (need_lock)
+		mutex_unlock(&dev->enable_mutex);
 	return err;
 }
 

@@ -1941,15 +1954,20 @@ void pci_disable_device(struct pci_dev *dev)
 	if (dr)
 		dr->enabled = 0;
 
+	mutex_lock(&dev->enable_mutex);
 	dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0,
 		      "disabling already-disabled device");
 
-	if (atomic_dec_return(&dev->enable_cnt) != 0)
+	if (atomic_dec_return(&dev->enable_cnt) != 0) {
+		mutex_unlock(&dev->enable_mutex);
 		return;
+	}
 
 	do_pci_disable_device(dev);
 
 	dev->is_busmaster = 0;
+
+	mutex_unlock(&dev->enable_mutex);
 }
 EXPORT_SYMBOL(pci_disable_device);
 

@@ -2427,6 +2427,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
 	INIT_LIST_HEAD(&dev->bus_list);
 	dev->dev.type = &pci_dev_type;
 	dev->bus = pci_bus_get(bus);
+	mutex_init(&dev->enable_mutex);
 
 	return dev;
 }

@@ -425,6 +425,7 @@ struct pci_dev {
 	unsigned int	no_vf_scan:1;		/* Don't scan for VFs after IOV enablement */
 	pci_dev_flags_t dev_flags;
 	atomic_t	enable_cnt;	/* pci_enable_device has been called */
+	struct mutex	enable_mutex;
 
 	u32		saved_config_space[16]; /* Config space saved at suspend time */
 	struct hlist_head saved_cap_space;

@@ -3526,6 +3526,13 @@
 		nomsi	Do not use MSI for native PCIe PME signaling (this makes
 			all PCIe root ports use INTx for all services).
 
+	pcie_movable_bars=[PCIE]
+			Override the movable BARs support detection:
+		off
+			Disable even if supported by the platform
+		force
+			Enable even if not explicitly declared as supported
+
 	pcmv=		[HW,PCMCIA] BadgePAD 4
 
 	pd_ignore_unused

@@ -1688,6 +1688,8 @@ static int __init pci_driver_init(void)
 {
 	int ret;
 
+	pci_add_flags(PCI_IMMOVABLE_BARS);
+
 	ret = bus_register(&pci_bus_type);
 	if (ret)
 		return ret;

@@ -139,6 +139,30 @@ static int __init pcie_port_pm_setup(char *str)
 }
 __setup("pcie_port_pm=", pcie_port_pm_setup);
 
+static bool pcie_movable_bars_off;
+static bool pcie_movable_bars_force;
+static int __init pcie_movable_bars_setup(char *str)
+{
+	if (!strcmp(str, "off"))
+		pcie_movable_bars_off = true;
+	else if (!strcmp(str, "force"))
+		pcie_movable_bars_force = true;
+	return 1;
+}
+__setup("pcie_movable_bars=", pcie_movable_bars_setup);
+
+bool pci_movable_bars_enabled(void)
+{
+	if (pcie_movable_bars_off)
+		return false;
+
+	if (pcie_movable_bars_force)
+		return true;
+
+	return !pci_has_flag(PCI_IMMOVABLE_BARS);
+}
+EXPORT_SYMBOL(pci_movable_bars_enabled);
+
 /* Time to wait after a reset for device to become responsive */
 #define PCIE_RESET_READY_POLL_MS 60000
 

@@ -257,6 +257,8 @@ bool pci_bus_clip_resource(struct pci_dev *dev, int idx);
 void pci_reassigndev_resource_alignment(struct pci_dev *dev);
 void pci_disable_bridge_window(struct pci_dev *dev);
 
+bool pci_dev_movable_bars_supported(struct pci_dev *dev);
+
 /* PCIe link information */
 #define PCIE_SPEED2STR(speed) \
 	((speed) == PCIE_SPEED_16_0GT ? "16 GT/s" : \

@@ -3406,6 +3406,74 @@ unsigned int pci_rescan_bus_bridge_resize(struct pci_dev *bridge)
 	return max;
 }
 
+bool pci_dev_movable_bars_supported(struct pci_dev *dev)
+{
+	if (!dev)
+		return false;
+
+	if (dev->driver && dev->driver->rescan_prepare)
+		return true;
+
+	if ((dev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
+		return false;
+
+	return !dev->driver;
+}
+
+void __weak pcibios_rescan_prepare(struct pci_dev *dev)
+{
+}
+
+void __weak pcibios_rescan_done(struct pci_dev *dev)
+{
+}
+
+static void pci_bus_rescan_prepare(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	if (bus->self)
+		pci_config_pm_runtime_get(bus->self);
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		struct pci_bus *child = dev->subordinate;
+
+		if (child)
+			pci_bus_rescan_prepare(child);
+
+		if (dev->driver &&
+		    dev->driver->rescan_prepare) {
+			dev->driver->rescan_prepare(dev);
+			pcibios_rescan_prepare(dev);
+		} else if (pci_dev_movable_bars_supported(dev)) {
+			pcibios_rescan_prepare(dev);
+		}
+	}
+}
+
+static void pci_bus_rescan_done(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		struct pci_bus *child = dev->subordinate;
+
+		if (dev->driver &&
+		    dev->driver->rescan_done) {
+			pcibios_rescan_done(dev);
+			dev->driver->rescan_done(dev);
+		} else if (pci_dev_movable_bars_supported(dev)) {
+			pcibios_rescan_done(dev);
+		}
+
+		if (child)
+			pci_bus_rescan_done(child);
+	}
+
+	if (bus->self)
+		pci_config_pm_runtime_put(bus->self);
+}
+
 /**
  * pci_rescan_bus - Scan a PCI bus for devices
  * @bus: PCI bus to scan

@@ -3418,9 +3486,23 @@ unsigned int pci_rescan_bus_bridge_resize(struct pci_dev *bridge)
 unsigned int pci_rescan_bus(struct pci_bus *bus)
 {
 	unsigned int max;
+	struct pci_bus *root = bus;
+
+	while (!pci_is_root_bus(root))
+		root = root->parent;
+
+	if (pci_movable_bars_enabled()) {
+		pci_bus_rescan_prepare(root);
+
+		max = pci_scan_child_bus(root);
+		pci_assign_unassigned_root_bus_resources(root);
+
+		pci_bus_rescan_done(root);
+	} else {
+		max = pci_scan_child_bus(bus);
+		pci_assign_unassigned_bus_resources(bus);
+	}
 
-	max = pci_scan_child_bus(bus);
-	pci_assign_unassigned_bus_resources(bus);
 	pci_bus_add_devices(bus);
 
 	return max;

@@ -838,6 +838,8 @@ struct pci_driver {
 	int  (*resume)(struct pci_dev *dev);	/* Device woken up */
 	void (*shutdown)(struct pci_dev *dev);
 	int  (*sriov_configure)(struct pci_dev *dev, int num_vfs); /* On PF */
+	void (*rescan_prepare)(struct pci_dev *dev);
+	void (*rescan_done)(struct pci_dev *dev);
 	const struct pci_error_handlers *err_handler;
 	const struct attribute_group **groups;
 	struct device_driver	driver;

@@ -924,6 +926,7 @@ enum {
 	PCI_ENABLE_PROC_DOMAINS	= 0x00000010,	/* Enable domains in /proc */
 	PCI_COMPAT_DOMAIN_0	= 0x00000020,	/* ... except domain 0 */
 	PCI_SCAN_ALL_PCIE_DEVS	= 0x00000040,	/* Scan all, not just dev 0 */
+	PCI_IMMOVABLE_BARS	= 0x00000080,	/* Disable runtime BAR reassign */
 };
 
 /* These external functions are only available when PCI support is enabled */

@@ -1266,6 +1269,9 @@ unsigned int pci_rescan_bus(struct pci_bus *bus);
 void pci_lock_rescan_remove(void);
 void pci_unlock_rescan_remove(void);
 
+void pcibios_rescan_prepare(struct pci_dev *dev);
+void pcibios_rescan_done(struct pci_dev *dev);
+
 /* Vital Product Data routines */
 ssize_t pci_read_vpd(struct pci_dev *dev, loff_t pos, size_t count, void *buf);
 ssize_t pci_write_vpd(struct pci_dev *dev, loff_t pos, size_t count, const void *buf);

@@ -1402,6 +1408,7 @@ unsigned char pci_bus_max_busnr(struct pci_bus *bus);
 void pci_setup_bridge(struct pci_bus *bus);
 resource_size_t pcibios_window_alignment(struct pci_bus *bus,
 					 unsigned long type);
+bool pci_movable_bars_enabled(void);
 
 #define PCI_VGA_STATE_CHANGE_BRIDGE (1 << 0)
 #define PCI_VGA_STATE_CHANGE_DECODES (1 << 1)

@@ -1482,6 +1482,55 @@ static void __pci_bridge_assign_resources(const struct pci_dev *bridge,
 	(IORESOURCE_IO | IORESOURCE_MEM | IORESOURCE_PREFETCH |\
 	 IORESOURCE_MEM_64)
 
+/*
+ * Similar to generic release_child_resources(), but aware of immovable BARs and
+ * PCI_FIXED and STARTALIGN flags
+ */
+static void pci_release_child_resources(struct pci_bus *bus, struct resource *r)
+{
+	struct pci_dev *dev;
+
+	if (!bus || !r)
+		return;
+
+	if (r->flags & IORESOURCE_PCI_FIXED)
+		return;
+
+	r->child = NULL;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		int i;
+
+		for (i = 0; i < PCI_NUM_RESOURCES; i++) {
+			struct resource *tmp = &dev->resource[i];
+			resource_size_t size = resource_size(tmp);
+
+			if (!tmp->flags || tmp->parent != r)
+				continue;
+
+			tmp->parent = NULL;
+			tmp->sibling = NULL;
+
+			pci_release_child_resources(dev->subordinate, tmp);
+
+			if ((tmp->flags & IORESOURCE_PCI_FIXED) ||
+			    !pci_dev_movable_bars_supported(dev)) {
+				pci_dbg(dev, "release immovable %pR (%s), keep its flags, base and size\n",
+					tmp, tmp->name);
+				continue;
+			}
+
+			pci_dbg(dev, "release %pR (%s)\n", tmp, tmp->name);
+
+			tmp->start = 0;
+			tmp->end = size - 1;
+
+			tmp->flags &= ~IORESOURCE_STARTALIGN;
+			tmp->flags |= IORESOURCE_SIZEALIGN;
+		}
+	}
+}
+
 static void pci_bridge_release_resources(struct pci_bus *bus,
 					 unsigned long type)
 {

@@ -1522,7 +1571,10 @@ static void pci_bridge_release_resources(struct pci_bus *bus,
 		return;
 
 	/* If there are children, release them all */
-	release_child_resources(r);
+	if (pci_movable_bars_enabled())
+		pci_release_child_resources(bus, r);
+	else
+		release_child_resources(r);
 	if (!release_resource(r)) {
 		type = old_flags = r->flags & PCI_RES_TYPE_MASK;
 		pci_info(dev, "resource %d %pR released\n",

@@ -295,7 +295,8 @@ static void assign_requested_resources_sorted(struct list_head *head,
 						    0 /* don't care */,
 						    0 /* don't care */);
 			}
-			reset_resource(res);
+			if (!pci_movable_bars_enabled())
+				reset_resource(res);
 		}
 	}
 }

@@ -1579,8 +1580,8 @@ static void pci_bridge_release_resources(struct pci_bus *bus,
 		type = old_flags = r->flags & PCI_RES_TYPE_MASK;
 		pci_info(dev, "resource %d %pR released\n",
 			 PCI_BRIDGE_RESOURCES + idx, r);
-		/* Keep the old size */
-		r->end = resource_size(r) - 1;
+		/* Don't keep the old size if the bridge will be recalculated */
+		r->end = pci_movable_bars_enabled() ? 0 : (resource_size(r) - 1);
 		r->start = 0;
 		r->flags = 0;
 

@@ -253,6 +253,7 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
 				struct list_head *realloc_head,
 				struct list_head *fail_head);
 bool pci_bus_clip_resource(struct pci_dev *dev, int idx);
+void pci_bus_release_root_bridge_resources(struct pci_bus *bus);
 
 void pci_reassigndev_resource_alignment(struct pci_dev *dev);
 void pci_disable_bridge_window(struct pci_dev *dev);

@@ -3474,6 +3474,25 @@ static void pci_bus_rescan_done(struct pci_bus *bus)
 		pci_config_pm_runtime_put(bus->self);
 }
 
+static void pci_setup_bridges(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		struct pci_bus *child;
+
+		if (!pci_dev_is_added(dev) || pci_dev_is_ignored(dev))
+			continue;
+
+		child = dev->subordinate;
+		if (child)
+			pci_setup_bridges(child);
+	}
+
+	if (bus->self)
+		pci_setup_bridge(bus);
+}
+
 /**
  * pci_rescan_bus - Scan a PCI bus for devices
  * @bus: PCI bus to scan

@@ -3495,8 +3514,11 @@ unsigned int pci_rescan_bus(struct pci_bus *bus)
 		pci_bus_rescan_prepare(root);
 
 		max = pci_scan_child_bus(root);
+
+		pci_bus_release_root_bridge_resources(root);
 		pci_assign_unassigned_root_bus_resources(root);
 
+		pci_setup_bridges(root);
 		pci_bus_rescan_done(root);
 	} else {
 		max = pci_scan_child_bus(bus);

@@ -1635,6 +1635,22 @@ static void pci_bus_release_bridge_resources(struct pci_bus *bus,
 		pci_bridge_release_resources(bus, type);
 }
 
+void pci_bus_release_root_bridge_resources(struct pci_bus *root_bus)
+{
+	int i;
+	struct resource *r;
+
+	pci_bus_release_bridge_resources(root_bus, IORESOURCE_IO, whole_subtree);
+	pci_bus_release_bridge_resources(root_bus, IORESOURCE_MEM, whole_subtree);
+	pci_bus_release_bridge_resources(root_bus,
+					 IORESOURCE_MEM_64 | IORESOURCE_PREFETCH,
+					 whole_subtree);
+
+	pci_bus_for_each_resource(root_bus, r, i) {
+		pci_release_child_resources(root_bus, r);
+	}
+}
+
 static void pci_bus_dump_res(struct pci_bus *bus)
 {
 	struct resource *res;

@@ -1011,12 +1011,21 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 			struct resource *r = &dev->resource[i];
 			resource_size_t r_size;
 
-			if (r->parent || (r->flags & IORESOURCE_PCI_FIXED) ||
+			if (r->parent ||
 			    ((r->flags & mask) != type &&
 			     (r->flags & mask) != type2 &&
 			     (r->flags & mask) != type3))
 				continue;
 			r_size = resource_size(r);
+
+			if ((r->flags & IORESOURCE_PCI_FIXED) ||
+			    !pci_dev_movable_bars_supported(dev)) {
+				if (pci_movable_bars_enabled())
+					size += r_size;
+
+				continue;
+			}
+
 #ifdef CONFIG_PCI_IOV
 			/* Put SRIOV requested res to the optional list */
 			if (realloc_head && i >= PCI_IOV_RESOURCES &&

@@ -373,6 +373,7 @@ static inline bool pci_dev_is_disconnected(const struct pci_dev *dev)
 
 /* pci_dev priv_flags */
 #define PCI_DEV_ADDED 0
+#define PCI_DEV_DISABLED_BARS 1
 
 static inline void pci_dev_assign_added(struct pci_dev *dev, bool added)
 {

@@ -384,6 +385,16 @@ static inline bool pci_dev_is_added(const struct pci_dev *dev)
 	return test_bit(PCI_DEV_ADDED, &dev->priv_flags);
 }
 
+static inline void pci_dev_disable_bars(struct pci_dev *dev)
+{
+	assign_bit(PCI_DEV_DISABLED_BARS, &dev->priv_flags, true);
+}
+
+static inline bool pci_dev_bars_enabled(const struct pci_dev *dev)
+{
+	return !test_bit(PCI_DEV_DISABLED_BARS, &dev->priv_flags);
+}
+
 #ifdef CONFIG_PCIEAER
 #include <linux/aer.h>
 

@@ -3428,6 +3428,23 @@ void __weak pcibios_rescan_done(struct pci_dev *dev)
 {
 }
 
+static unsigned int pci_dev_count_res_mask(struct pci_dev *dev)
+{
+	unsigned int res_mask = 0;
+	int i;
+
+	for (i = 0; i < PCI_BRIDGE_RESOURCES; i++) {
+		struct resource *r = &dev->resource[i];
+
+		if (!r->flags || (r->flags & IORESOURCE_UNSET) || !r->parent)
+			continue;
+
+		res_mask |= (1 << i);
+	}
+
+	return res_mask;
+}
+
 static void pci_bus_rescan_prepare(struct pci_bus *bus)
 {
 	struct pci_dev *dev;

@@ -3438,6 +3455,8 @@ static void pci_bus_rescan_prepare(struct pci_bus *bus)
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		struct pci_bus *child = dev->subordinate;
 
+		dev->res_mask = pci_dev_count_res_mask(dev);
+
 		if (child)
 			pci_bus_rescan_prepare(child);
 

@@ -3481,7 +3500,7 @@ static void pci_setup_bridges(struct pci_bus *bus)
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		struct pci_bus *child;
 
-		if (!pci_dev_is_added(dev) || pci_dev_is_ignored(dev))
+		if (!pci_dev_is_added(dev) || !pci_dev_bars_enabled(dev))
 			continue;
 
 		child = dev->subordinate;

@@ -3493,6 +3512,83 @@ static void pci_setup_bridges(struct pci_bus *bus)
 		pci_setup_bridge(bus);
 }
 
+static struct pci_dev *pci_find_next_new_device(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	if (!bus)
+		return NULL;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		struct pci_bus *child_bus = dev->subordinate;
+
+		if (!pci_dev_is_added(dev) && pci_dev_bars_enabled(dev))
+			return dev;
+
+		if (child_bus) {
+			struct pci_dev *next_new_dev;
+
+			next_new_dev = pci_find_next_new_device(child_bus);
+			if (next_new_dev)
+				return next_new_dev;
+		}
+	}
+
+	return NULL;
+}
+
+static bool pci_bus_check_all_bars_reassigned(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+	bool ret = true;
+
+	if (!bus)
+		return false;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		struct pci_bus *child = dev->subordinate;
+		unsigned int res_mask = pci_dev_count_res_mask(dev);
+
+		if (!pci_dev_bars_enabled(dev))
+			continue;
+
+		if (dev->res_mask & ~res_mask) {
+			pci_err(dev, "Non-re-enabled resources found: 0x%x -> 0x%x\n",
+				dev->res_mask, res_mask);
+			ret = false;
+		}
+
+		if (child && !pci_bus_check_all_bars_reassigned(child))
+			ret = false;
+	}
+
+	return ret;
+}
+
+static void pci_reassign_root_bus_resources(struct pci_bus *root)
+{
+	do {
+		struct pci_dev *next_new_dev;
+
+		pci_bus_release_root_bridge_resources(root);
+		pci_assign_unassigned_root_bus_resources(root);
+
+		if (pci_bus_check_all_bars_reassigned(root))
+			break;
+
+		next_new_dev = pci_find_next_new_device(root);
+		if (!next_new_dev) {
+			dev_err(&root->dev, "failed to re-assign resources even after ignoring all the hotplugged devices\n");
+			break;
+		}
+
+		dev_warn(&root->dev, "failed to re-assign resources, disable the next hotplugged device %s and retry\n",
+			 dev_name(&next_new_dev->dev));
+
+		pci_dev_disable_bars(next_new_dev);
+	} while (true);
+}
+
 /**
  * pci_rescan_bus - Scan a PCI bus for devices
  * @bus: PCI bus to scan

@@ -3515,8 +3611,7 @@ unsigned int pci_rescan_bus(struct pci_bus *bus)
 
 		max = pci_scan_child_bus(root);
 
-		pci_bus_release_root_bridge_resources(root);
-		pci_assign_unassigned_root_bus_resources(root);
+		pci_reassign_root_bus_resources(root);
 
 		pci_setup_bridges(root);
 		pci_bus_rescan_done(root);

@@ -128,6 +128,9 @@ static void pdev_sort_resources(struct pci_dev *dev, struct list_head *head)
 {
 	int i;
 
+	if (!pci_dev_bars_enabled(dev))
+		return;
+
 	for (i = 0; i < PCI_NUM_RESOURCES; i++) {
 		struct resource *r;
 		struct pci_dev_resource *dev_res, *tmp;

@@ -177,6 +180,9 @@ static void __dev_sort_resources(struct pci_dev *dev, struct list_head *head)
 {
 	u16 class = dev->class >> 8;
 
+	if (!pci_dev_bars_enabled(dev))
+		return;
+
 	/* Don't touch classless devices or host bridges or IOAPICs */
 	if (class == PCI_CLASS_NOT_DEFINED || class == PCI_CLASS_BRIDGE_HOST)
 		return;

@@ -278,6 +284,9 @@ static void assign_requested_resources_sorted(struct list_head *head,
 	int idx;
 
 	list_for_each_entry(dev_res, head, list) {
+		if (!pci_dev_bars_enabled(dev_res->dev))
+			continue;
+
 		res = dev_res->res;
 		idx = res - &dev_res->dev->resource[0];
 		if (resource_size(res) &&

@@ -995,6 +1004,9 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		int i;
 
+		if (!pci_dev_bars_enabled(dev))
+			continue;
+
 		for (i = 0; i < PCI_NUM_RESOURCES; i++) {
 			struct resource *r = &dev->resource[i];
 			resource_size_t r_size;

@@ -1349,6 +1361,9 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
 	pbus_assign_resources_sorted(bus, realloc_head, fail_head);
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
+		if (!pci_dev_bars_enabled(dev))
+			continue;
+
 		pdev_assign_fixed_resources(dev);
 
 		b = dev->subordinate;

@@ -375,6 +375,7 @@ struct pci_dev {
 	 */
 	unsigned int	irq;
 	struct resource resource[DEVICE_COUNT_RESOURCE]; /* I/O and memory regions + expansion ROMs */
+	unsigned int	res_mask;		/* Bitmask of assigned resources */
 
 	bool		match_driver;		/* Skip attaching driver */
 

@@ -1819,6 +1819,13 @@ void pci_assign_unassigned_root_bus_resources(struct pci_bus *bus)
 	int pci_try_num = 1;
 	enum enable_type enable_local;
 
+	if (pci_movable_bars_enabled()) {
+		__pci_bus_size_bridges(bus, NULL);
+		__pci_bus_assign_resources(bus, NULL, NULL);
+
+		goto dump;
+	}
+
 	/* Don't realloc if asked to do so */
 	enable_local = pci_realloc_detect(bus, pci_realloc_enable);
 	if (pci_realloc_enabled(enable_local)) {

@@ -1356,6 +1356,8 @@ static void pdev_assign_fixed_resources(struct pci_dev *dev)
 		while (b && !r->parent) {
 			assign_fixed_resource_on_bus(b, r);
 			b = b->parent;
+			if (!r->parent && pci_movable_bars_enabled())
+				break;
 		}
 	}
 }

@@ -298,6 +298,18 @@ static int _pci_assign_resource(struct pci_dev *dev, int resno,
 
 	bus = dev->bus;
 	while ((ret = __pci_assign_resource(bus, dev, resno, size, min_align))) {
+		if (pci_movable_bars_enabled()) {
+			if (resno >= PCI_BRIDGE_RESOURCES &&
+			    resno <= PCI_BRIDGE_RESOURCE_END) {
+				struct resource *res = dev->resource + resno;
+
+				res->start = 0;
+				res->end = 0;
+				res->flags = 0;
+			}
+			break;
+		}
+
 		if (!bus->parent || !bus->self->transparent)
 			break;
 		bus = bus->parent;

@@ -371,6 +371,20 @@ static inline bool pci_dev_is_disconnected(const struct pci_dev *dev)
 	return dev->error_state == pci_channel_io_perm_failure;
 }
 
+static inline int pci_get_bridge_resource_idx(struct resource *r)
+{
+	int idx = 1;
+
+	if (r->flags & IORESOURCE_IO)
+		idx = 0;
+	else if (!(r->flags & IORESOURCE_PREFETCH))
+		idx = 1;
+	else if (r->flags & IORESOURCE_MEM_64)
+		idx = 2;
+
+	return idx;
+}
+
 /* pci_dev priv_flags */
 #define PCI_DEV_ADDED 0
 #define PCI_DEV_DISABLED_BARS 1

@@ -550,6 +550,7 @@ void pci_read_bridge_bases(struct pci_bus *child)
 static struct pci_bus *pci_alloc_bus(struct pci_bus *parent)
 {
 	struct pci_bus *b;
+	int idx;
 
 	b = kzalloc(sizeof(*b), GFP_KERNEL);
 	if (!b)

@@ -566,6 +567,11 @@ static struct pci_bus *pci_alloc_bus(struct pci_bus *parent)
 	if (parent)
 		b->domain_nr = parent->domain_nr;
 #endif
+	for (idx = 0; idx < PCI_BRIDGE_RESOURCE_NUM; ++idx) {
+		b->immovable_range[idx].start = 0;
+		b->immovable_range[idx].end = 0;
+	}
+
 	return b;
 }
 

@@ -3512,6 +3518,87 @@ static void pci_setup_bridges(struct pci_bus *bus)
 		pci_setup_bridge(bus);
 }
 
+static void pci_bus_update_immovable_range(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+	int idx;
+	resource_size_t start, end;
+
+	for (idx = 0; idx < PCI_BRIDGE_RESOURCE_NUM; ++idx) {
+		bus->immovable_range[idx].start = 0;
+		bus->immovable_range[idx].end = 0;
+	}
+
+	list_for_each_entry(dev, &bus->devices, bus_list)
+		if (dev->subordinate)
+			pci_bus_update_immovable_range(dev->subordinate);
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		int i;
+		bool dev_is_movable = pci_dev_movable_bars_supported(dev);
+		struct pci_bus *child = dev->subordinate;
+
+		for (i = 0; i < PCI_BRIDGE_RESOURCES; ++i) {
+			struct resource *r = &dev->resource[i];
+
+			if (!r->flags || (r->flags & IORESOURCE_UNSET) || !r->parent)
+				continue;
+
+			if (!dev_is_movable || (r->flags & IORESOURCE_PCI_FIXED)) {
+				idx = pci_get_bridge_resource_idx(r);
+				start = bus->immovable_range[idx].start;
+				end = bus->immovable_range[idx].end;
+
+				if (!start || start > r->start)
+					start = r->start;
+				if (end < r->end)
+					end = r->end;
+
+				if (bus->immovable_range[idx].start != start ||
+				    bus->immovable_range[idx].end != end) {
+					dev_dbg(&bus->dev, "Found fixed 0x%llx-0x%llx in %s, expand the fixed bridge window %d to 0x%llx-0x%llx\n",
+						(unsigned long long)r->start,
+						(unsigned long long)r->end,
+						dev_name(&dev->dev), idx,
+						(unsigned long long)start,
+						(unsigned long long)end);
+					bus->immovable_range[idx].start = start;
+					bus->immovable_range[idx].end = end;
+				}
+			}
+		}
+
+		if (child) {
+			for (idx = 0; idx < PCI_BRIDGE_RESOURCE_NUM; ++idx) {
+				struct resource *child_immovable_range =
+					&child->immovable_range[idx];
+
+				if (child_immovable_range->start >=
+				    child_immovable_range->end)
+					continue;
+
+				start = bus->immovable_range[idx].start;
+				end = bus->immovable_range[idx].end;
+
+				if (!start || start > child_immovable_range->start)
+					start = child_immovable_range->start;
+				if (end < child_immovable_range->end)
+					end = child_immovable_range->end;
+
+				if (start < bus->immovable_range[idx].start ||
+				    end > bus->immovable_range[idx].end) {
+					dev_dbg(&bus->dev, "Expand the fixed bridge window %d from %s to 0x%llx-0x%llx\n",
+						idx, dev_name(&child->dev),
+						(unsigned long long)start,
+						(unsigned long long)end);
+					bus->immovable_range[idx].start = start;
+					bus->immovable_range[idx].end = end;
+				}
+			}
+		}
+	}
+}
+
 static struct pci_dev *pci_find_next_new_device(struct pci_bus *bus)
 {
 	struct pci_dev *dev;

@@ -3610,6 +3697,7 @@ unsigned int pci_rescan_bus(struct pci_bus *bus)
 		pci_bus_rescan_prepare(root);
 
 		max = pci_scan_child_bus(root);
+		pci_bus_update_immovable_range(root);
 
 		pci_reassign_root_bus_resources(root);
 

@@ -882,9 +882,17 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 	resource_size_t children_add_size = 0;
 	resource_size_t min_align, align;
 
+	resource_size_t fixed_start = bus->immovable_range[0].start;
+	resource_size_t fixed_end = bus->immovable_range[0].end;
+	resource_size_t fixed_size = (fixed_start < fixed_end) ?
+		(fixed_end - fixed_start + 1) : 0;
+
 	if (!b_res)
 		return;
 
+	if (min_size < fixed_size)
+		min_size = fixed_size;
+
 	min_align = window_alignment(bus, IORESOURCE_IO);
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		int i;

@@ -993,6 +1001,15 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 	resource_size_t children_add_size = 0;
 	resource_size_t children_add_align = 0;
 	resource_size_t add_align = 0;
+	bool is_mem64 = (mask & IORESOURCE_MEM_64);
+
+	resource_size_t fixed_start = bus->immovable_range[is_mem64 ? 2 : 1].start;
+	resource_size_t fixed_end = bus->immovable_range[is_mem64 ? 2 : 1].end;
+	resource_size_t fixed_size = (fixed_start < fixed_end) ?
+		(fixed_end - fixed_start + 1) : 0;
+
+	if (min_size < fixed_size)
+		min_size = fixed_size;
 
 	if (!b_res)
 		return -ENOSPC;

@@ -581,6 +581,12 @@ struct pci_bus {
 	struct list_head resources;	/* Address space routed to this bus */
 	struct resource busn_res;	/* Bus numbers routed to this bus */
 
+	/*
+	 * If there are fixed or immovable resources in the bridge window, this range
+	 * contains the lowest start address and highest end address of them.
+	 */
+	struct resource immovable_range[PCI_BRIDGE_RESOURCE_NUM];
+
 	struct pci_ops	*ops;		/* Configuration access functions */
 	struct msi_controller *msi;	/* MSI controller */
 	void		*sysdata;	/* Hook for sys-specific extension */

@@ -1819,6 +1819,72 @@ static enum enable_type pci_realloc_detect(struct pci_bus *bus,
 }
 #endif
 
+/*
+ * Calculate the address margins where the bridge windows may be allocated to fit all
+ * the fixed and immovable BARs beneath.
+ */
+static void pci_bus_update_realloc_range(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+	struct pci_bus *parent = bus->parent;
+	int idx;
+
+	list_for_each_entry(dev, &bus->devices, bus_list)
+		if (dev->subordinate)
+			pci_bus_update_realloc_range(dev->subordinate);
+
+	if (!parent || !bus->self)
+		return;
+
+	for (idx = 0; idx < PCI_BRIDGE_RESOURCE_NUM; ++idx) {
+		struct resource *immovable_range = &bus->immovable_range[idx];
+		resource_size_t window_size = resource_size(bus->resource[idx]);
+		resource_size_t realloc_start, realloc_end;
+
+		bus->realloc_range[idx].start = 0;
+		bus->realloc_range[idx].end = 0;
+
+		/* Check if there any immovable BARs under the bridge */
+		if (immovable_range->start >= immovable_range->end)
+			continue;
+
+		/* The lowest possible address where the bridge window can start */
+		realloc_start = immovable_range->end - window_size + 1;
+		/* The highest possible address where the bridge window can end */
+		realloc_end = immovable_range->start + window_size - 1;
+
+		if (realloc_start > immovable_range->start)
+			realloc_start = immovable_range->start;
+
+		if (realloc_end < immovable_range->end)
+			realloc_end = immovable_range->end;
+
+		/*
+		 * Check that realloc range doesn't intersect with hard fixed ranges
+		 * of neighboring bridges
+		 */
+		list_for_each_entry(dev, &parent->devices, bus_list) {
+			struct pci_bus *neighbor = dev->subordinate;
+			struct resource *n_imm_range;
+
+			if (!neighbor || neighbor == bus)
+				continue;
+
+			n_imm_range = &neighbor->immovable_range[idx];
+
+			if (n_imm_range->start >= n_imm_range->end)
+				continue;
+
+			if (n_imm_range->end < immovable_range->start &&
+			    n_imm_range->end > realloc_start)
+				realloc_start = n_imm_range->end;
+		}
+
+		bus->realloc_range[idx].start = realloc_start;
+		bus->realloc_range[idx].end = realloc_end;
+	}
+}
+
 /*
  * First try will not touch PCI bridge res.
  * Second and later try will clear small leaf bridge res.