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

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Message-Id: <20250816151929.197589-1-yeoreum.yun@arm.com>
Date: Sat, 16 Aug 2025 16:19:23 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: catalin.marinas@....com,
	will@...nel.org,
	broonie@...nel.org,
	maz@...nel.org,
	oliver.upton@...ux.dev,
	joey.gouly@....com,
	james.morse@....com,
	ardb@...nel.org,
	scott@...amperecomputing.com,
	suzuki.poulose@....com,
	yuzenghui@...wei.com,
	mark.rutland@....com
Cc: linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH RESEND v7 0/6] support FEAT_LSUI and apply it on futex atomic ops

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
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}