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

Yeoreum Yun
2025-09-01T10:07:48Z

Gentle ping in case of forgotten.

On Sat, Aug 16, 2025 at 04:19:23PM +0100, 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
> 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}
>

--
Sincerely,
Yeoreum Yun