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.

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 support futext atomic-op with FEAT_LSUI

Patch History
==============
from v7 to v8:
  - implements futex_atomic_eor() and futex_atomic_cmpxchg() with casalt
    with C helper.
  - Drop the small optimisation on ll/sc futex_atomic_set operation.
  - modify some commit message.
  - https://lore.kernel.org/all/20250816151929.197589-1-yeoreum.yun@arm.com/

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 (5):
  arm64: cpufeature: add FEAT_LSUI
  KVM: arm64: expose FEAT_LSUI to guest
  arm64: Kconfig: Detect toolchain support for LSUI
  arm64: futex: refactor futex atomic operation
  arm64: futex: support futex with FEAT_LSUI

 arch/arm64/Kconfig             |   5 +
 arch/arm64/include/asm/futex.h | 262 +++++++++++++++++++++++++++------
 arch/arm64/kernel/cpufeature.c |  10 ++
 arch/arm64/kvm/sys_regs.c      |   5 +-
 arch/arm64/tools/cpucaps       |   1 +
 5 files changed, 235 insertions(+), 48 deletions(-)

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