Public bug reported:
Summary
Fixes an amd64 build break in the merged CXL VFIO Type-2 passthrough v2 series:
drivers/vfio/pci/cxl/vfio_cxl_core.c uses FIELD_GET() without including
<linux/bitfield.h>. Adds the missing include.
The failure
On amd64 (resolute:linux-nvidia-bos), the build fails with:
drivers/vfio/pci/cxl/vfio_cxl_core.c:267:14: error: implicit declaration
of function 'FIELD_GET' [-Wimplicit-function-declaration]
Root cause
vfio_cxl_core.c calls FIELD_GET() (to decode the CXL DVSEC capability
register) but never includes <linux/bitfield.h>, where that macro is defined.
It compiled only because of an architecture-dependent transitive include:
On arm64, <linux/bitfield.h> is pulled in indirectly via
linux/slab.h -> linux/cache.h -> arch/arm64/include/asm/cache.h ->
asm/cputype.h -> asm/sysreg.h, and arm64's asm/sysreg.h includes
<linux/bitfield.h>.
On amd64 that arm64-only header chain does not exist, so FIELD_GET
is undefined and the build fails.
The nvidia-bos kernel is built for both amd64 and arm64
(CONFIG_VFIO_CXL_CORE=y on both), so the file must not rely on any one
architecture's transitive include graph.
Fix
Add #include <linux/bitfield.h> directly to vfio_cxl_core.c
(include-what-you-use), making the file architecture-independent.
Scope
This is only needed for the v2 posting of the CXL VFIO Type-2 passthrough
series (commit 3570209d539a). v3 and later of that upstream series
already include <linux/bitfield.h> in this file directly, so the change
becomes redundant and drops out naturally once the tree moves to v3+.
Fixes: 3570209 ("NVIDIA: VR: SAUCE: vfio/cxl: Virtualize CXL DVSEC
config writes")
** Affects: linux-nvidia-bos (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2163376
Title:
vfio/cxl: include <linux/bitfield.h> for FIELD_GET to fix amd64 build
break
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