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

[Ilpo Järvinen]

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:
> > 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.