PCI: Enable unassigned resource reallocation on per-bus basis

pci_realloc_detect() turns on automatic resource allocation when it finds
unassigned SR-IOV resources.  Previously it did this on a global basis, so
we enabled reallocation if any PCI device anywhere had an unassigned SR-IOV
resource.

This patch changes pci_realloc_detect() so it looks at a single bus, so we
can do this when a host bridge is hot-added.

[bhelgaas: changelog]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/setup-bus.c

@@ -1354,9 +1354,9 @@ void __init pci_realloc_get_opt(char *str)
 	else if (!strncmp(str, "on", 2))
 		pci_realloc_enable = user_enabled;
 }
-static bool __init pci_realloc_enabled(void)
+static bool __init pci_realloc_enabled(enum enable_type enable)
 {
-	return pci_realloc_enable >= user_enabled;
+	return enable >= user_enabled;
 }
 
 #if defined(CONFIG_PCI_IOV) && defined(CONFIG_PCI_REALLOC_ENABLE_AUTO)
@@ -1383,24 +1383,26 @@ static int __init iov_resources_unassigned(struct pci_dev *dev, void *data)
 	return 0;
 }
 
-static void  __init pci_realloc_detect(void)
+static enum enable_type __init pci_realloc_detect(struct pci_bus *bus,
+			 enum enable_type enable_local)
 {
 	bool unassigned = false;
-	struct pci_bus *bus;
 
-	if (pci_realloc_enable != undefined)
-		return;
+	if (enable_local != undefined)
+		return enable_local;
 
-	list_for_each_entry(bus, &pci_root_buses, node) {
-		pci_walk_bus(bus, iov_resources_unassigned, &unassigned);
-		if (unassigned) {
-			pci_realloc_enable = auto_enabled;
-			return;
-		}
-	}
+	pci_walk_bus(bus, iov_resources_unassigned, &unassigned);
+	if (unassigned)
+		return auto_enabled;
+
+	return enable_local;
 }
 #else
-static void __init pci_realloc_detect(void) { }
+static enum enable_type __init pci_realloc_detect(struct pci_bus *bus,
+			 enum enable_type enable_local)
+{
+	return enable_local;
+}
 #endif
 
 /*
@@ -1422,10 +1424,12 @@ pci_assign_unassigned_resources(void)
 	unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM |
 				  IORESOURCE_PREFETCH;
 	int pci_try_num = 1;
+	enum enable_type enable_local = pci_realloc_enable;
 
-	/* don't realloc if asked to do so */
-	pci_realloc_detect();
-	if (pci_realloc_enabled()) {
+	list_for_each_entry(bus, &pci_root_buses, node)
+		enable_local = pci_realloc_detect(bus, enable_local);
+
+	if (pci_realloc_enabled(enable_local)) {
 		int max_depth = pci_get_max_depth();
 
 		pci_try_num = max_depth + 1;
@@ -1457,9 +1461,9 @@ again:
 		goto enable_and_dump;
 
 	if (tried_times >= pci_try_num) {
-		if (pci_realloc_enable == undefined)
+		if (enable_local == undefined)
 			printk(KERN_INFO "Some PCI device resources are unassigned, try booting with pci=realloc\n");
-		else if (pci_realloc_enable == auto_enabled)
+		else if (enable_local == auto_enabled)
 			printk(KERN_INFO "Automatically enabled pci realloc, if you have problem, try booting with pci=realloc=off\n");
 
 		free_list(&fail_head);