Re: [PATCH v3 00/11] PCI: Resizable BAR improvements

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Oct 23, 2025 at 05:02:42PM -0500, Lucas De Marchi wrote:
> On Thu, Oct 23, 2025 at 04:29:43PM -0500, Bjorn Helgaas wrote:
> > On Wed, Oct 22, 2025 at 04:33:20PM +0300, Ilpo Järvinen wrote:
> > > pci.c has been used as catch everything that doesn't fits elsewhere
> > > within PCI core and thus resizable BAR code has been placed there as
> > > well. Move Resizable BAR related code to a newly introduced rebar.c to
> > > reduce size of pci.c. After move, there are no pci_rebar_*() calls from
> > > pci.c indicating this is indeed well-defined subset of PCI core.
> > > 
> > > Endpoint drivers perform Resizable BAR related operations which could
> > > well be performed by PCI core to simplify driver-side code. This
> > > series adds a few new API functions to that effect and converts the
> > > drivers to use the new APIs (in separate patches).
> > > 
> > > While at it, also convert BAR sizes bitmask to u64 as PCIe spec already
> > > specifies more sizes than what will fit u32 to make the API typing more
> > > future-proof. The extra sizes beyond 128TB are not added at this point.
> > > 
> > > Some parts of this are to be used by the resizable BAR changes into the
> > > resource fitting/assingment logic but these seem to stand on their own
> > > so sending these out now to reduce the size of the other patch series.
> > > 
> > > v3:
> > > - Rebased to solve minor conflicts
> > > 
> > > v2: https://lore.kernel.org/linux-pci/20250915091358.9203-1-ilpo.jarvinen@linux.intel.com/
> > > - Kerneldoc:
> > >   - Improve formatting of errno returns
> > >   - Open "ctrl" -> "control"
> > >   - Removed mislead "bit" words (when referring to BAR size)
> > >   - Rewrote pci_rebar_get_possible_sizes() kernel doc to not claim the
> > >     returned bitmask is defined in PCIe spec as the capability bits now
> > >     span across two registers in the spec and are not continuous (we
> > >     don't support the second block of bits yet, but this API is expected
> > >     to return the bits without the hole so it will not be matching with
> > >     the spec layout).
> > > - Dropped superfluous zero check from pci_rebar_size_supported()
> > > - Small improvement to changelog of patch 7
> > > 
> > > Ilpo Järvinen (11):
> > >   PCI: Move Resizable BAR code into rebar.c
> > >   PCI: Cleanup pci_rebar_bytes_to_size() and move into rebar.c
> > >   PCI: Move pci_rebar_size_to_bytes() and export it
> > >   PCI: Improve Resizable BAR functions kernel doc
> > >   PCI: Add pci_rebar_size_supported() helper
> > >   drm/i915/gt: Use pci_rebar_size_supported()
> > >   drm/xe/vram: Use PCI rebar helpers in resize_vram_bar()
> > >   PCI: Add pci_rebar_get_max_size()
> > >   drm/xe/vram: Use pci_rebar_get_max_size()
> > >   drm/amdgpu: Use pci_rebar_get_max_size()
> > >   PCI: Convert BAR sizes bitmasks to u64
> > > 
> > >  Documentation/driver-api/pci/pci.rst        |   3 +
> > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c  |   8 +-
> > >  drivers/gpu/drm/i915/gt/intel_region_lmem.c |  10 +-
> > >  drivers/gpu/drm/xe/xe_vram.c                |  32 +-
> > >  drivers/pci/Makefile                        |   2 +-
> > >  drivers/pci/iov.c                           |   9 +-
> > >  drivers/pci/pci-sysfs.c                     |   2 +-
> > >  drivers/pci/pci.c                           | 145 ---------
> > >  drivers/pci/pci.h                           |   5 +-
> > >  drivers/pci/rebar.c                         | 314 ++++++++++++++++++++
> > >  drivers/pci/setup-res.c                     |  78 -----
> > >  include/linux/pci.h                         |  15 +-
> > >  12 files changed, 350 insertions(+), 273 deletions(-)
> > >  create mode 100644 drivers/pci/rebar.c
> > 
> > Applied to pci/rebar for v6.18, thanks, Ilpo!
> 
> is this for v6.18 or it's a typo and it's going to v6.19?

Oops, sorry, I meant v6.19!  I still have v6.18 regressions top of
mind :)

> > If we have follow-on resource assignment changes that depend on these,
> > maybe I'll rename the branch to be more generic before applying them.
> > 
> > Also applied the drivers/gpu changes based on the acks.  I see the CI
> > merge failures since this series is based on v6.18-rc1; I assume the
> > CI applies to current linux-next or similar.  I'll check the conflicts
> 
> it tries on drm-tip that contains drm-xe-next going to v6.19. We have
> some changes there that conflict, but shouldn't be hard.
> 
> We also need https://lore.kernel.org/linux-pci/20250918-xe-pci-rebar-2-v1-1-6c094702a074@intel.com/
> to actually fix the rebar in some cases. Could you take a look?

Will do.  Remind me again if I forget!

Bjorn