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Subject[PATCH 1/1] PCI: allocate essential resources before reserving hotplug resources
    PCI: reserve  additional  resources  for hotplug bridges
only after all essential resources are allocated.

Linux tries to reserve minimal resources for hotplug
bridges. This works fine as long as there are enough
resources to satisfy all other essential resource
requirements. However if enough resources are not
available to satisfy both the essential resources
and the reservation for hotplug resources, the
resource-allocator reports error and returns failure.

This patch distinguishes between essential resources and
nice-to-have resources. 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
requests caused by not-so-smart allocation behavior of
the native BIOS.

https://bugzilla.kernel.org/show_bug.cgi?id=15960
captures the details of the issue and the motivation
behind this patch.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>

drivers/pci/setup-bus.c | 142 +++++++++++++++++++++++++++++++++++-------------
include/linux/ioport.h | 1
2 files changed, 105 insertions(+), 38 deletions(-)
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 66cb8f4..76a7fb7 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -91,7 +91,26 @@ static void __dev_sort_resources(struct pci_dev *dev,
pdev_sort_resources(dev, head);
}

-static void __assign_resources_sorted(struct resource_list *head,
+
+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 (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;
@@ -114,14 +133,25 @@ static void __assign_resources_sorted(struct resource_list *head,
}
res->start = 0;
res->end = 0;
+ res->add_size = 0;
res->flags = 0;
}
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 +434,37 @@ 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 +487,16 @@ 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);
+ if (add_size)
+ size1 = calculate_iosize(size, min_size+add_size, size1,
+ resource_size(b_res), 4096);
+ else
+ size1 = size;
+
+ 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 +507,35 @@ 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 +583,6 @@ 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 +597,14 @@ 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);
+ if (add_size)
+ size1 = calculate_memsize(size, min_size+add_size, 0, resource_size(b_res), align);
+ else
+ size1 = size;
+
+ 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 +614,8 @@ 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 +672,7 @@ 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 +703,11 @@ 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 +715,11 @@ 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..d00c61c 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;
const char *name;
unsigned long flags;
struct resource *parent, *sibling, *child;

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