[RFC,v8,12/12] x86/PCI: add MMCFG information on demand

diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
index b2652e9..0c0c1a7 100644
--- a/arch/x86/include/asm/pci_x86.h
+++ b/arch/x86/include/asm/pci_x86.h
@@ -142,6 +142,11 @@  extern int __devinit pci_mmconfig_insert(struct device *dev,
 					 u16 seg, u8 start,
 					 u8 end, phys_addr_t addr);
 extern int pci_mmconfig_delete(u16 seg, u8 start, u8 end);
+#if defined(CONFIG_ACPI) && defined(CONFIG_PCI_MMCONFIG)
+extern void pci_mmconfig_probe(u8 start);
+#else
+static inline void pci_mmconfig_probe(u8 start) { }
+#endif
 extern struct pci_mmcfg_region *pci_mmconfig_lookup(int segment, int bus);
 
 extern struct list_head pci_mmcfg_list;
diff --git a/arch/x86/pci/legacy.c b/arch/x86/pci/legacy.c
index a1df191..e9a2384 100644
--- a/arch/x86/pci/legacy.c
+++ b/arch/x86/pci/legacy.c
@@ -49,6 +49,7 @@  void __devinit pcibios_scan_specific_bus(int busn)
 		    l != 0x0000 && l != 0xffff) {
 			DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);
 			printk(KERN_INFO "PCI: Discovered peer bus %02x\n", busn);
+			pci_mmconfig_probe(busn);
 			pci_scan_bus_on_node(busn, &pci_root_ops, node);
 			return;
 		}
diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
index f8c967c..330831c 100644
--- a/arch/x86/pci/mmconfig-shared.c
+++ b/arch/x86/pci/mmconfig-shared.c
@@ -459,6 +459,14 @@  static int __ref is_mmconf_reserved(check_reserved_t is_reserved,
 			break;
 	}
 
+	/*
+	 * For backward compatibility, we will adjust the MMCONFIG region
+	 * at boot time if it's only partially reserved by firmware.
+	 * For PCI host bridge hotplug at runtime, just reject it.
+	 */
+	if (pci_mmcfg_running_state && old_size != size)
+		return 0;
+
 	if (size < (16UL<<20) && size != old_size)
 		return 0;
 
@@ -602,6 +610,16 @@  static int __init pci_parse_mcfg(struct acpi_table_header *header)
 			return -ENODEV;
 		}
 
+		/*
+		 * MMCFG information for host brideges will be added on demand
+		 * by pci_root driver if ACPI is enabled. But there are special
+		 * requirements for devices on segment 0, MMCFG information may
+		 * be needed for fixing hardware quirks and probing for hidden
+		 * buses.
+		 */
+		if (!acpi_disabled && cfg->pci_segment)
+			continue;
+
 		if (pci_mmconfig_add(cfg->pci_segment, cfg->start_bus_number,
 				   cfg->end_bus_number, cfg->address) == NULL) {
 			printk(KERN_WARNING PREFIX
@@ -614,7 +632,7 @@  static int __init pci_parse_mcfg(struct acpi_table_header *header)
 	return 0;
 }
 
-static void __init __pci_mmcfg_init(int early)
+static void __init __pci_mmcfg_init(int early, bool create_on_demand)
 {
 	pci_mmcfg_reject_broken(early);
 	if (list_empty(&pci_mmcfg_list))
@@ -630,6 +648,13 @@  static void __init __pci_mmcfg_init(int early)
 		}
 	}
 
+	/*
+	 * Avoid redundant pci_mmcfg_arch_map()/pci_mmcfg_arch_unmap() calls
+	 * for each MMCONFIG entry if they will be created on demand.
+	 */
+	if (create_on_demand)
+		free_all_mmcfg();
+
 	if (pci_mmcfg_arch_init())
 		pci_probe = (pci_probe & ~PCI_PROBE_MASK) | PCI_PROBE_MMCONF;
 	else {
@@ -647,28 +672,37 @@  void __init pci_mmcfg_early_init(void)
 			known_bridge = 1;
 		else
 			acpi_sfi_table_parse(ACPI_SIG_MCFG, pci_parse_mcfg);
-		__pci_mmcfg_init(1);
+		__pci_mmcfg_init(1, false);
 	}
 }
 
 void __init pci_mmcfg_late_init(void)
 {
+	bool create_on_demand;
+
 	/* MMCONFIG disabled */
 	if ((pci_probe & PCI_PROBE_MMCONF) == 0)
 		return;
 
-	/* MMCONFIG already enabled */
-	if (!(pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF))
-		return;
-
 	if (known_bridge)
 		return;
 
-	acpi_sfi_table_parse(ACPI_SIG_MCFG, pci_parse_mcfg);
-	__pci_mmcfg_init(0);
+	/*
+	 * MMCONFIG information will be created on demand by pci_root driver
+	 * when binding to ACPI host bridge deivces.
+	 */
+	create_on_demand = (!acpi_disabled && !acpi_pci_cache_mcfg());
 
-	if (!(pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF))
-		acpi_pci_cache_mcfg();
+	/* pci_mmcfg_early_init() fails to setup MMCONFIG, try again. */
+	if (pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF) {
+		acpi_sfi_table_parse(ACPI_SIG_MCFG, pci_parse_mcfg);
+		__pci_mmcfg_init(0, create_on_demand);
+	/*
+	 * Free MMCONFIG information created by pci_mmcfg_early_init()
+	 * if MMCONFIG information will be created on demand.
+	 */
+	} else if (create_on_demand)
+		free_all_mmcfg();
 }
 
 static int __init pci_mmcfg_late_insert_resources(void)
@@ -802,3 +836,25 @@  int pci_mmconfig_delete(u16 seg, u8 start, u8 end)
 
 	return -ENOENT;
 }
+
+#ifdef	CONFIG_ACPI
+/* Probe MMCFG information for PCI bus blind probe */
+void __devinit pci_mmconfig_probe(u8 start)
+{
+	int end_bus, temp;
+	phys_addr_t addr;
+
+	if (!(pci_probe & PCI_PROBE_MMCONF) || pci_mmcfg_arch_init_failed)
+		return;
+
+	addr = acpi_pci_root_get_mcfg_addr(NULL, 0, start, &end_bus);
+	if (addr && end_bus >= 0 && end_bus <= 255) {
+		for (temp = start + 1; temp <= end_bus; temp++)
+			if (pci_find_bus(0, temp))
+				break;
+
+		temp--;
+		pci_mmconfig_insert(NULL, 0, start, (u8) temp, addr);
+	}
+}
+#endif