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

On Thu, 26 Mar 2026, Bjorn Helgaas wrote:

[+cc Xifer; thanks very much for reporting and testing!]

On Tue, Mar 24, 2026 at 06:56:23PM +0200, Ilpo Järvinen wrote:

quoted

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(-)

I added Xifer's tested-by, fixed the "am68k" and missing "if"
typos, and applied these to pci/resource for v7.1.

Ilpo, if you post a v2 with more changes, I'll update to it.  I
applied the series now to get a head start on 0-day building and into
next.

Thanks.

I don't have anything in addition to those.

-- 
 i.