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

Will Deacon
2025-09-15T20:37:24Z

On Thu, Sep 11, 2025 at 05:22:22PM +0100, Catalin Marinas wrote:
> On Thu, Sep 11, 2025 at 04:09:42PM +0100, Will Deacon wrote:
> > 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?
>
> Unfortunately, it's just in the public xml at the moment. Hopefully
> we'll get a release of the Arm ARM by the end of the year. Otherwise, in
> the private 2024 arch spec. Not ideal though.

Ah, thanks, the xml is a *lot* better than nothing.

> If you'd rather wait until in turns up in the public spec, fine by me.

As long as you're happy to continue helping with the review, I think
it's fine.

Cheers,

Will