linux-kernel - [PATCH v2 0/6] support FEAT_LSUI and apply it on futex atomic ops

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Message-Id: <20250611151154.46362-1-yeoreum.yun@arm.com>
Date: Wed, 11 Jun 2025 16:11:48 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: catalin.marinas@....com,
	will@...nel.org,
	broonie@...nel.org,
	maz@...nel.org,
	oliver.upton@...ux.dev,
	ardb@...nel.org,
	frederic@...nel.org,
	james.morse@....com,
	joey.gouly@....com,
	scott@...amperecomputing.com
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH v2 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_LUSI 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_LUSI

Patch #2 adds Kconfig for FEAT_LUSI

Patch #3 separtes former futex atomic-op implmentation from futex.h
to futex_ll_sc_u.h

Patch #4 implments futex atomic operation using lsui instruction.

Patch #5 introduces lsui.h to apply runtime patch to use former
implmentation when FEAT_LUSI doesn't support.

Patch #6 applies lsui.h into arch_futext_atomic_op().

Patch History
==============
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
  arm64/Kconfig: add LSUI Kconfig
  arm64/futex: move futex atomic logic with clearing PAN bit
  arm64/futex: add futex atomic operation with FEAT_LSUI
  arm64/asm: introduce lsui.h
  arm64/futex: support futex with FEAT_LSUI

 arch/arm64/Kconfig                     |   3 +
 arch/arm64/include/asm/futex.h         |  99 ++++++-------------
 arch/arm64/include/asm/futex_ll_sc_u.h | 115 +++++++++++++++++++++
 arch/arm64/include/asm/futex_lsui.h    | 132 +++++++++++++++++++++++++
 arch/arm64/include/asm/lsui.h          |  37 +++++++
 arch/arm64/kernel/cpufeature.c         |   8 ++
 arch/arm64/tools/cpucaps               |   1 +
 7 files changed, 327 insertions(+), 68 deletions(-)
 create mode 100644 arch/arm64/include/asm/futex_ll_sc_u.h
 create mode 100644 arch/arm64/include/asm/futex_lsui.h
 create mode 100644 arch/arm64/include/asm/lsui.h

--
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