Re: [PATCH 00/11] PCI: pci_resource_alignment() improvement + cleanups

[Bjorn Helgaas]

On Wed, Apr 29, 2026 at 03:26:06PM +0300, Ilpo Järvinen wrote:
> pci_resource_alignment() returns 0 when resource is already assigned
> and in case of disabled bridge windows. This has caused problems to
> calculations relying on pci_resource_alignment():
> 
> https://lore.kernel.org/linux-pci/LV8P221MB1472A24B9975F7C8E8D6BF929947A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> This series reworks pci_resource_alignment() interface to return always
> non-zero alignment if the resource exists. For assigned bridge windows,
> the calculation is using heuristic based on size and start address
> alignment as calculating the alignment again is costly (would require
> sizing the entire sub-hierarchy).
> 
> As pci_resource_alignment() is becoming more complicated, it's also
> moved to setup-res.c. While moving pci_resource_alignment()'s arguments
> are converted into const to tell compiler it can rely on resource
> remaining the same across the call.
> 
> This was intended to be part of a larger series that addresses some
> shortcomings in pci=realloc. The pci=realloc changes will recalculate
> bridge window sizes considering also assigned resources which required
> making these changes to pci_resource_alignment().
> 
> As this also relates to the issue linked above, I'm sending it already
> now without pci=realloc changes that are still incomplete. The first
> patches originate from the large pci=realloc work but seem generally
> useful even if independent of the alignment improvements so I've
> included them here without reorganizing the series to contain only
> alignment related changes.
> 
> Ilpo Järvinen (11):
>   PCI: Log all resource claims
>   PCI: Rename added to add_list
>   PCI: Consolidate add_list (aka realloc_head) empty sanity checks
>   PCI: Remove const removal cast
>   resource: Make resource_alignment() input const resource
>   powerpc/pseries: Make pseries_get_iov_fw_value() & pnv_iov_get()
>     pci_dev const
>   PCI: Make pci_sriov_resource_alignment() pci_dev const
>   PCI: Convert pci_resource_alignment() input parameters to const
>   PCI: Move pci_resource_alignment() to setup-res.c file
>   PCI: Lower bound bridge windown alignment
>   PCI: Return valid alignment for assigned resources
> 
>  arch/powerpc/include/asm/machdep.h         |  2 +-
>  arch/powerpc/kernel/pci-common.c           |  2 +-
>  arch/powerpc/platforms/powernv/pci-sriov.c |  4 +-
>  arch/powerpc/platforms/powernv/pci.h       |  5 ++-
>  arch/powerpc/platforms/pseries/setup.c     |  5 ++-
>  drivers/pci/iov.c                          |  7 +--
>  drivers/pci/pci.h                          | 24 ++++-------
>  drivers/pci/setup-bus.c                    | 50 ++++++++++++----------
>  drivers/pci/setup-cardbus.c                |  2 +-
>  drivers/pci/setup-res.c                    | 37 ++++++++++++++++
>  include/linux/ioport.h                     |  2 +-
>  include/linux/pci.h                        |  8 ++--
>  kernel/resource.c                          |  2 +-
>  13 files changed, 94 insertions(+), 56 deletions(-)

Applied to pci/resource for v7.2, thanks!

Powerpc folks, the arch/powerpc changes here are minor (just adding
const), but heads up in case you see any issue.