linux-kernel - Re: [PATCH v12 0/7] support FEAT

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Message-ID: <aYWuqTqM5MvudI5V@e129823.arm.com>
Date: Fri, 6 Feb 2026 09:04:41 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Cc: catalin.marinas@....com, will@...nel.org, maz@...nel.org,
	broonie@...nel.org, oliver.upton@...ux.dev, miko.lenczewski@....com,
	kevin.brodsky@....com, ardb@...nel.org, suzuki.poulose@....com,
	lpieralisi@...nel.org, scott@...amperecomputing.com,
	joey.gouly@....com, yuzenghui@...wei.com, pbonzini@...hat.com,
	shuah@...nel.org, mark.rutland@....com, arnd@...db.de
Subject: Re: [PATCH v12 0/7] support FEAT_LSUI

Gentle ping in case of forgotten.

On Wed, Jan 21, 2026 at 07:06:15PM +0000, Yeoreum Yun wrote:
> 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
> and user_swpX emulation where can replace from ldxr/st{l}xr
> pair implmentation with clearing PSTATE.PAN bit to correspondant
> load/store unprevileged atomic operation without clearing PSTATE.PAN bit.
>
> This patch based on v6.19-rc6
>
> Patch History
> ==============
> from v11 to v12:
>   - rebase to v6.19-rc6
>   - add CONFIG_ARM64_LSUI
>   - enable LSUI when !CPU_BIG_ENDIAN and PAN presents.
>   - drop the swp emulation with LSUI insns instead, disable it
>     when LSUI presents.
>   - some of small fixes (useless prefix and suffix and etc).
>   - https://lore.kernel.org/all/20251214112248.901769-1-yeoreum.yun@arm.com/
>
> from v10 to v11:
>   - rebase to v6.19-rc1
>   - use cast instruction to emulate deprecated swpb instruction
>   - https://lore.kernel.org/all/20251103163224.818353-1-yeoreum.yun@arm.com/
>
> from v9 to v10:
>   - apply FEAT_LSUI to user_swpX emulation.
>   - add test coverage for LSUI bit in ID_AA64ISAR3_EL1
>   - rebase to v6.18-rc4
>   - https://lore.kernel.org/all/20250922102244.2068414-1-yeoreum.yun@arm.com/
>
> from v8 to v9:
>   - refotoring __lsui_cmpxchg64()
>   - rebase to v6.17-rc7
>   - https://lore.kernel.org/all/20250917110838.917281-1-yeoreum.yun@arm.com/
>
> 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_LSUI to guest
>   - add help section for LSUI 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_LSUI in cpucaps in order
>   - https://lore.kernel.org/all/20250611104916.10636-1-yeoreum.yun@arm.com/
>
>
> Yeoreum Yun (7):
>   arm64: Kconfig: add support for LSUI
>   arm64: cpufeature: add FEAT_LSUI
>   KVM: arm64: expose FEAT_LSUI to guest
>   KVM: arm64: kselftest: set_id_regs: add test for FEAT_LSUI
>   arm64: futex: refactor futex atomic operation
>   arm64: futex: support futex with FEAT_LSUI
>   arm64: armv8_deprecated: disable swp emulation when FEAT_LSUI present
>
>  arch/arm64/Kconfig                            |  20 ++
>  arch/arm64/include/asm/futex.h                | 322 +++++++++++++++---
>  arch/arm64/kernel/armv8_deprecated.c          |  16 +
>  arch/arm64/kernel/cpufeature.c                |  27 ++
>  arch/arm64/kvm/sys_regs.c                     |   3 +-
>  arch/arm64/tools/cpucaps                      |   1 +
>  .../testing/selftests/kvm/arm64/set_id_regs.c |   1 +
>  7 files changed, 339 insertions(+), 51 deletions(-)
>
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>

--
Sincerely,
Yeoreum Yun