[PATCH RESEND v7 0/6] support FEAT_LSUI and apply it on futex atomic ops

Yeoreum Yun
2025-08-16T15:19:34Z

Since Armv9.6, FEAT_LSUI supplies the load/store instructions for
previleged level to access to access user memory without clearing
PSTATE.PAN bit.

This patchset support FEAT_LSUI and applies in futex atomic operation
where can replace from ldxr/stlxr pair implmentation with clearing
PSTATE.PAN bit to correspondant load/store unprevileged atomic operation
without clearing PSTATE.PAN bit.

(Sorry, I've sent wrongly for patch version 7 and resend it.
Again, sorry for mail-boom).

Patch Sequences
================

Patch #1 adds cpufeature for FEAT_LSUI

Patch #2 expose FEAT_LSUI to guest

Patch #3 adds Kconfig for FEAT_LSUI

Patch #4 refactor former futex atomic-op implmentation with ll/sc &
clearing PSTATE.PAN

Patch #5 applies small optimisation for __llc_futex_atomic_set().

Patch #6 support futext atomic-op with FEAT_LSUI

Patch History
==============
from v6 to v7:
- wrap FEAT_LSUI with CONFIG_AS_HAS_LSUI in cpufeature
- remove unnecessary addition of indentation.
- remove unnecessary mte_tco_enable()/disable() on LSUI operation.
- https://lore.kernel.org/all/20250811163635.1562145-1-yeoreum.yun@arm.com/

from v5 to v6:
- rebase to v6.17-rc1
- https://lore.kernel.org/all/20250722121956.1509403-1-yeoreum.yun@arm.com/

from v4 to v5:
- remove futex_ll_sc.h futext_lsui and lsui.h and move them to futex.h
- reorganize the patches.
- https://lore.kernel.org/all/20250721083618.2743569-1-yeoreum.yun@arm.com/

from v3 to v4:
- rebase to v6.16-rc7
- modify some patch's title.
- https://lore.kernel.org/all/20250617183635.1266015-1-yeoreum.yun@arm.com/

from v2 to v3:
- expose FEAT_LUSI to guest
- add help section for LUSI Kconfig
- https://lore.kernel.org/all/20250611151154.46362-1-yeoreum.yun@arm.com/

from v1 to v2:
- remove empty v9.6 menu entry
- locate HAS_LUSI in cpucaps in order
- https://lore.kernel.org/all/20250611104916.10636-1-yeoreum.yun@arm.com/

Yeoreum Yun (6):
arm64: cpufeature: add FEAT_LSUI
KVM: arm64: expose FEAT_LSUI to guest
arm64: Kconfig: add LSUI Kconfig
arm64: futex: refactor futex atomic operation
arm64: futex: small optimisation for __llsc_futex_atomic_set()
arm64: futex: support futex with FEAT_LSUI

arch/arm64/Kconfig | 5 +
arch/arm64/include/asm/futex.h | 291 +++++++++++++++++++++++++++------
arch/arm64/kernel/cpufeature.c | 10 ++
arch/arm64/kvm/sys_regs.c | 5 +-
arch/arm64/tools/cpucaps | 1 +
5 files changed, 261 insertions(+), 51 deletions(-)

base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
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LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}