On Tue, Dec 30, 2025 at 08:08:44AM +0100, Thomas Weißschuh wrote:

The cache parameter of getcpu() is useless nowadays for various reasons.
* It is never passed by userspace for either the vDSO or syscalls.
* It is never used by the kernel.
* It could not be made to work on the current vDSO architecture.
* The structure definition is not part of the UAPI headers.
* vdso_getcpu() is superseded by restartable sequences in any case.

Remove the struct and its header.

As a side-effect we get rid of an unwanted inclusion of the linux/
header namespace from vDSO code.

Signed-off-by: Thomas Weißschuh <redacted>
---
Changes in v3:
- Rebase on v6.19-rc1
  - Fix conflict with UML vdso_getcpu() removal
- Flesh out commit message
- Link to v2: https://lore.kernel.org/r/20251013-getcpu_cache-v2-1-880fbfa3b7cc@linutronix.de (local)

Changes in v2:
- Rebase on v6.18-rc1
- Link to v1: https://lore.kernel.org/r/20250826-getcpu_cache-v1-1-8748318f6141@linutronix.de (local)
---
We could also completely remove the parameter, but I am not sure if
that is a good idea for syscalls and vDSO entrypoints.
---
 arch/loongarch/vdso/vgetcpu.c                   |  5 ++---
 arch/s390/kernel/vdso/getcpu.c                  |  3 +--
 arch/s390/kernel/vdso/vdso.h                    |  4 +---
 arch/x86/entry/vdso/vgetcpu.c                   |  5 ++---
 arch/x86/include/asm/vdso/processor.h           |  4 +---
 include/linux/getcpu.h                          | 19 -------------------
 include/linux/syscalls.h                        |  3 +--
 kernel/sys.c                                    |  4 +---
 tools/testing/selftests/vDSO/vdso_test_getcpu.c |  4 +---
 9 files changed, 10 insertions(+), 41 deletions(-)

Acked-by: Heiko Carstens <hca@linux.ibm.com> # s390