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

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Message-ID: <aMLmNnehYX6gqEIf@willie-the-truck>
Date: Thu, 11 Sep 2025 16:09:42 +0100
From: Will Deacon <will@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, 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,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v7 0/6] support FEAT_LSUI and apply it on futex
 atomic ops

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).

I tried to review this but I can't find any details about FEAT_LSUI in
the latest Arm ARM. Where should I be looking for the architecture spec?

Will