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

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Message-ID: <20251023212943.GA1323026@bhelgaas>
Date: Thu, 23 Oct 2025 16:29:43 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Christian König <christian.koenig@....com>,
	Michał Winiarski <michal.winiarski@...el.com>,
	Alex Deucher <alexander.deucher@....com>,
	amd-gfx@...ts.freedesktop.org, David Airlie <airlied@...il.com>,
	dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
	intel-xe@...ts.freedesktop.org,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Simona Vetter <simona@...ll.ch>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	"Michael J . Ruhl" <mjruhl@...ana.ai>,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 00/11] PCI: Resizable BAR improvements

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!

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
later and we can defer those changes if needed.