[PATCH 00/10] PCI: Improve head free space usage

Ilpo Järvinen
2026-03-24T16:58:27Z

Hi all,

This series attempts to take advantage of free head space (the free
space before the aligned start address) in order to generally produce a
tighter packing of the resources/bridge windows.

The recent changes to the resource fitting algorithm caused resource
allocation failures in some cases where a bridge window that is sized
to be gapless could no longer be assigned. The previous algorithm left
a huge gaps which allowed it to place the remainder (non-aligning part
of the size) before the start address of used for the gapless fit,
whereas the new gapless approach always had to place the remainder
after the aligning part of the resources. There is not always space
for the remainder triggering those failures (e.g., when the aligning
part must be placed at the top of the window).

This series attempts to allow placing the remainder once again before
the aligning part, but now without leaving huge gaps to retain the
benefits of the gapless bridge windows. The approach is somewhat hacky
but should work thanks to PCI resources fundamentally consisting only
power-of-two atoms.

There maybe cases where architecture would not want to do such
relocation. This series adds the relocation to arch
pcibios_align_resource() functions to allow all of them taking
advantage of the better resource packing but if somebody objects doing
this relocation for a particular arch, I can remove it, please just let
me know (this relocation doesn't seem critical unless there are
regressions).

Ilpo Järvinen (10):
resource: Add __resource_contains_unbound() for internal contains
checks
resource: Pass full extent of empty space to resource_alignf CB
resource: Rename 'tmp' variable to 'full_avail'
ARM/PCI: Remove unnecessary second application of align
am68k/PCI: Remove unnecessary second application of align
MIPS: PCI: Remove unnecessary second application of align
parisc/PCI: Cleanup align handling
PCI: Rename window_alignment() to pci_min_window_alignment()
PCI: Align head space better
PCI: Fix alignment calculation for resource size larger than align

arch/alpha/kernel/pci.c | 1 +
arch/arm/kernel/bios32.c | 9 ++++---
arch/m68k/kernel/pcibios.c | 8 +++++--
arch/mips/pci/pci-generic.c | 8 ++++---
arch/mips/pci/pci-legacy.c | 3 +++
arch/parisc/kernel/pci.c | 17 ++++++++------
arch/powerpc/kernel/pci-common.c | 6 ++++-
arch/s390/pci/pci.c | 1 +
arch/sh/drivers/pci/pci.c | 6 ++++-
arch/x86/pci/i386.c | 5 +++-
arch/xtensa/kernel/pci.c | 3 +++
drivers/pci/pci.h | 3 +++
drivers/pci/setup-bus.c | 15 ++++++++----
drivers/pci/setup-res.c | 40 +++++++++++++++++++++++++++++++-
drivers/pcmcia/rsrc_nonstatic.c | 3 ++-
include/linux/ioport.h | 22 +++++++++++++++---
include/linux/pci.h | 12 +++++++---
kernel/resource.c | 33 +++++++++++++-------------
18 files changed, 149 insertions(+), 46 deletions(-)

base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
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2.39.5