[PATCH 1/3] x86/PCI: allocate space from the end of a region, not the beginning

[Bjorn Helgaas <bjorn.helgaas@hp.com>]

Allocate from the end of a region, not the beginning.

For example, if we need to allocate 0x800 bytes for a device on bus
0000:00 given these resources:

    [mem 0xbff00000-0xdfffffff] PCI Bus 0000:00
      [mem 0xc0000000-0xdfffffff] PCI Bus 0000:02

the available space at [mem 0xbff00000-0xbfffffff] is passed to the
alignment callback (pcibios_align_resource()).  Prior to this patch, we
would put the new 0x800 byte resource at the beginning of that available
space, i.e., at [mem 0xbff00000-0xbff007ff].

With this patch, we put it at the end, at [mem 0xbffff800-0xbfffffff].

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=16228#c41
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
---

 arch/x86/pci/i386.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)


diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
index 5525309..1ff3e9f 100644
--- a/arch/x86/pci/i386.c
+++ b/arch/x86/pci/i386.c
@@ -65,7 +65,10 @@ pcibios_align_resource(void *data, const struct resource *res,
 			resource_size_t size, resource_size_t align)
 {
 	struct pci_dev *dev = data;
-	resource_size_t start = res->start;
+	resource_size_t start = ALIGN(res->end - size + 1, align);
+
+	if (start < res->start)
+		start = res->start;
 
 	if (res->flags & IORESOURCE_IO) {
 		if (skip_isa_ioresource_align(dev))