Commit dc9887dc authored Oct 26, 2010 by Bjorn Helgaas Committed by Jesse Barnes Oct 26, 2010

x86/PCI: allocate space from the end of a region, not the beginning

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>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

parent b126b470

arch/x86/pci/i386.c

+11 −6

Original line number	Diff line number	Diff line
		@@ -65,16 +65,21 @@ 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 = round_down(res->end - size + 1, align);

		if (res->flags & IORESOURCE_IO) {
		if (skip_isa_ioresource_align(dev))
		return start;
		if (start & 0x300)
		start = (start + 0x3ff) & ~0x3ff;

		/*
		* If we're avoiding ISA aliases, the largest contiguous I/O
		* port space is 256 bytes. Clearing bits 9 and 10 preserves
		* all 256-byte and smaller alignments, so the result will
		* still be correctly aligned.
		*/
		if (!skip_isa_ioresource_align(dev))
		start &= ~0x300;
		} else if (res->flags & IORESOURCE_MEM) {
		if (start < BIOS_END)
		start = BIOS_END;
		start = res->end; /* fail; no space */
		}
		return start;
		}