[PATCH 1/1 Version 2.0] PCI: allocate essential resources before reserving hotplug resources

[Ram Pai <linuxram@us.ibm.com>]

        PCI: pre-allocate additional resources to devices
        only after successful allocation of essential resources.
    
        Linux tries to pre-allocate minimal resources to hotplug
        bridges.  This  works   fine as long as there are enough
        resources  to  satisfy   all   other   genuine  resource
        requirements.  However  if  enough  resources   are  not
        available to   satisfy   any   of   these   nice-to-have
        pre-allocations, the  resource-allocator reports  errors
        and returns failure.
    
        This patch distinguishes between must-have resource from
        nice-to-have   resource.   Any    failure   to  allocate
        nice-to-have resources are ignored.
    
        This  behavior  can  be  particularly  useful to trigger
        automatic  reallocation, if  the  OS  discovers  genuine
        resource  allocation  conflicts  or  genuine unallocated
        resource requests caused   by  buggy allocation behavior
        of the native BIOS/uEFI.
    
        https://bugzilla.kernel.org/show_bug.cgi?id=15960
        captures the movitation behind the patch.
        This patch is verified to resolve the above bug.
    
Signed-off-by: Ram Pai <linuxram@us.ibm.com>

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 66cb8f4..5b0fb2f 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -91,7 +91,39 @@ static void __dev_sort_resources(struct pci_dev *dev,
 	pdev_sort_resources(dev, head);
 }
 
-static void __assign_resources_sorted(struct resource_list *head,
+static inline void reset_resource(struct resource *res)
+{
+	res->start = 0;
+	res->end = 0;
+	res->add_size = 0;
+	res->flags = 0;
+}
+
+static void adjust_resources_sorted(struct resource_list *head)
+{
+	struct resource *res;
+	struct resource_list *list, *tmp;
+	int idx;
+
+	for (list = head->next; list;) {
+		res = list->res;
+		idx = res - &list->dev->resource[0];
+
+		if (!resource_size(res) && res->add_size) {
+			 res->end = res->start + res->add_size - 1;
+			 if(pci_assign_resource(list->dev, idx))
+				reset_resource(res);
+		} else if (res->add_size) {
+			adjust_resource(res, res->start, 
+				resource_size(res) + res->add_size);
+		}
+		tmp = list;
+		list = list->next;
+		kfree(tmp);
+	}
+}
+
+static void assign_requested_resources_sorted(struct resource_list *head,
 				 struct resource_list_x *fail_head)
 {
 	struct resource *res;
@@ -102,7 +134,7 @@ static void __assign_resources_sorted(struct resource_list *head,
 		res = list->res;
 		idx = res - &list->dev->resource[0];
 
-		if (pci_assign_resource(list->dev, idx)) {
+		if (resource_size(res) && pci_assign_resource(list->dev, idx)) {
 			if (fail_head && !pci_is_root_bus(list->dev->bus)) {
 				/*
 				 * if the failed res is for ROM BAR, and it will
@@ -112,16 +144,24 @@ static void __assign_resources_sorted(struct resource_list *head,
 				      (!(res->flags & IORESOURCE_ROM_ENABLE))))
 					add_to_failed_list(fail_head, list->dev, res);
 			}
-			res->start = 0;
-			res->end = 0;
-			res->flags = 0;
+			reset_resource(res);
 		}
 		tmp = list;
 		list = list->next;
-		kfree(tmp);
 	}
 }
 
+static void __assign_resources_sorted(struct resource_list *head,
+				 struct resource_list_x *fail_head)
+{
+	/* Satisfy the must-have resource requests */
+	assign_requested_resources_sorted(head, fail_head);
+
+	/* Try to satisfy any additional nice-to-have resource 
+		requests */
+	adjust_resources_sorted(head);
+}
+
 static void pdev_assign_resources_sorted(struct pci_dev *dev,
 				 struct resource_list_x *fail_head)
 {
@@ -404,15 +444,37 @@ static struct resource *find_free_bus_resource(struct pci_bus *bus, unsigned lon
 	return NULL;
 }
 
+static resource_size_t calculate_iosize(resource_size_t size, 
+		resource_size_t min_size, 
+		resource_size_t size1, 
+		resource_size_t old_size, 
+		resource_size_t align)
+{
+	if (size < min_size)
+		size = min_size;
+	if (old_size == 1 )
+		old_size = 0;
+	/* To be fixed in 2.5: we should have sort of HAVE_ISA
+	   flag in the struct pci_bus. */
+#if defined(CONFIG_ISA) || defined(CONFIG_EISA)
+	size = (size & 0xff) + ((size & ~0xffUL) << 2);
+#endif
+	size = ALIGN(size + size1, align);
+	if (size < old_size)
+		size = old_size;
+	return size;
+}
+
 /* Sizing the IO windows of the PCI-PCI bridge is trivial,
    since these windows have 4K granularity and the IO ranges
    of non-bridge PCI devices are limited to 256 bytes.
    We must be careful with the ISA aliasing though. */
-static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
+static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size, 
+			resource_size_t add_size)
 {
 	struct pci_dev *dev;
 	struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO);
-	unsigned long size = 0, size1 = 0, old_size;
+	unsigned long size = 0, size1 = 0;
 
 	if (!b_res)
  		return;
@@ -435,20 +497,14 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
 				size1 += r_size;
 		}
 	}
-	if (size < min_size)
-		size = min_size;
-	old_size = resource_size(b_res);
-	if (old_size == 1)
-		old_size = 0;
-/* To be fixed in 2.5: we should have sort of HAVE_ISA
-   flag in the struct pci_bus. */
-#if defined(CONFIG_ISA) || defined(CONFIG_EISA)
-	size = (size & 0xff) + ((size & ~0xffUL) << 2);
-#endif
-	size = ALIGN(size + size1, 4096);
-	if (size < old_size)
-		size = old_size;
-	if (!size) {
+
+	size = calculate_iosize(size, min_size, size1, 
+			resource_size(b_res), 4096);
+	size1 = !add_size? size: 
+		calculate_iosize(size, min_size+add_size, size1, 
+			resource_size(b_res), 4096);
+
+	if (!size && !size1) {
 		if (b_res->start || b_res->end)
 			dev_info(&bus->self->dev, "disabling bridge window "
 				 "%pR to [bus %02x-%02x] (unused)\n", b_res,
@@ -459,16 +515,35 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
 	/* Alignment of the IO window is always 4K */
 	b_res->start = 4096;
 	b_res->end = b_res->start + size - 1;
+	b_res->add_size = size1-size;
 	b_res->flags |= IORESOURCE_STARTALIGN;
 }
 
+
+static resource_size_t calculate_memsize(resource_size_t size, 
+		resource_size_t min_size, 
+		resource_size_t size1, 
+		resource_size_t old_size, 
+		resource_size_t align)
+{
+	if (size < min_size)
+		size = min_size;
+	if (old_size == 1 )
+		old_size = 0;
+	if (size < old_size)
+		size = old_size;
+	size = ALIGN(size + size1, align);
+	return size;
+}
+
 /* Calculate the size of the bus and minimal alignment which
    guarantees that all child resources fit in this size. */
 static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
-			 unsigned long type, resource_size_t min_size)
+			 unsigned long type, resource_size_t min_size, 
+				resource_size_t add_size)
 {
 	struct pci_dev *dev;
-	resource_size_t min_align, align, size, old_size;
+	resource_size_t min_align, align, size, size1;
 	resource_size_t aligns[12];	/* Alignments from 1Mb to 2Gb */
 	int order, max_order;
 	struct resource *b_res = find_free_bus_resource(bus, type);
@@ -516,13 +591,6 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 			mem64_mask &= r->flags & IORESOURCE_MEM_64;
 		}
 	}
-	if (size < min_size)
-		size = min_size;
-	old_size = resource_size(b_res);
-	if (old_size == 1)
-		old_size = 0;
-	if (size < old_size)
-		size = old_size;
 
 	align = 0;
 	min_align = 0;
@@ -537,8 +605,13 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 			min_align = align1 >> 1;
 		align += aligns[order];
 	}
-	size = ALIGN(size, min_align);
-	if (!size) {
+
+	size = calculate_memsize(size, min_size, 0, resource_size(b_res), align);
+	size1 = !add_size ? size : 
+		calculate_memsize(size, min_size+add_size, 0, 
+				resource_size(b_res), align);
+
+	if (!size && !size1) {
 		if (b_res->start || b_res->end)
 			dev_info(&bus->self->dev, "disabling bridge window "
 				 "%pR to [bus %02x-%02x] (unused)\n", b_res,
@@ -548,8 +621,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 	}
 	b_res->start = min_align;
 	b_res->end = size + min_align - 1;
-	b_res->flags |= IORESOURCE_STARTALIGN;
-	b_res->flags |= mem64_mask;
+	b_res->add_size = size1 - size;
+	b_res->flags |= IORESOURCE_STARTALIGN | mem64_mask;
 	return 1;
 }
 
@@ -606,7 +679,7 @@ void __ref pci_bus_size_bridges(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
 	unsigned long mask, prefmask;
-	resource_size_t min_mem_size = 0, min_io_size = 0;
+	resource_size_t additional_mem_size = 0, additional_io_size = 0;
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		struct pci_bus *b = dev->subordinate;
@@ -637,11 +710,11 @@ void __ref pci_bus_size_bridges(struct pci_bus *bus)
 	case PCI_CLASS_BRIDGE_PCI:
 		pci_bridge_check_ranges(bus);
 		if (bus->self->is_hotplug_bridge) {
-			min_io_size  = pci_hotplug_io_size;
-			min_mem_size = pci_hotplug_mem_size;
+			additional_io_size  = pci_hotplug_io_size;
+			additional_mem_size = pci_hotplug_mem_size;
 		}
 	default:
-		pbus_size_io(bus, min_io_size);
+		pbus_size_io(bus, 0, additional_io_size);
 		/* If the bridge supports prefetchable range, size it
 		   separately. If it doesn't, or its prefetchable window
 		   has already been allocated by arch code, try
@@ -649,11 +722,11 @@ void __ref pci_bus_size_bridges(struct pci_bus *bus)
 		   resources. */
 		mask = IORESOURCE_MEM;
 		prefmask = IORESOURCE_MEM | IORESOURCE_PREFETCH;
-		if (pbus_size_mem(bus, prefmask, prefmask, min_mem_size))
+		if (pbus_size_mem(bus, prefmask, prefmask, 0, additional_mem_size))
 			mask = prefmask; /* Success, size non-prefetch only. */
 		else
-			min_mem_size += min_mem_size;
-		pbus_size_mem(bus, mask, IORESOURCE_MEM, min_mem_size);
+			additional_mem_size += additional_mem_size;
+		pbus_size_mem(bus, mask, IORESOURCE_MEM, 0, additional_mem_size);
 		break;
 	}
 }
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index e9bb22c..70b4ae6 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -18,6 +18,7 @@
 struct resource {
 	resource_size_t start;
 	resource_size_t end;
+	resource_size_t add_size; /* additional nice-to-have resource */
 	const char *name;
 	unsigned long flags;
 	struct resource *parent, *sibling, *child;