linux-kernel - Re: [PATCH 3/8] s390/entry: shorten OUTSIDE macro

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Message-ID: <CAKwvOdmSBNsA7C2ZCGDEmuxCituSQ=HPJx=9+AsBAOYfkSZRPA@mail.gmail.com>
Date:   Thu, 12 May 2022 11:00:31 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Jonas Paulsson <paulsson@...ux.vnet.ibm.com>,
        Ulrich Weigand <ulrich.weigand@...ibm.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Andreas Krebbel <krebbel@...ux.ibm.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 3/8] s390/entry: shorten OUTSIDE macro

On Thu, May 12, 2022 at 10:22 AM Heiko Carstens <hca@...ux.ibm.com> wrote:
>
> On Wed, May 11, 2022 at 02:05:27PM +0200, Heiko Carstens wrote:
> > Since the minimum architecture level has been raised to z10 a shorter
> > instruction sequence can be used to implement the OUTSIDE macro. This
> > also reduces the number of used registers within that macro to one.
> >
> > Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
> > ---
> >  arch/s390/kernel/entry.S | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
> > index a6b45eaa3450..e1664b45090f 100644
> > --- a/arch/s390/kernel/entry.S
> > +++ b/arch/s390/kernel/entry.S
> > @@ -169,11 +169,9 @@ _LPP_OFFSET      = __LC_LPP
> >        * @outside_label: jump here if @reg is outside of [@start..@end)
> >        */
> >       .macro OUTSIDE reg,start,end,outside_label
> > -     lgr     %r14,\reg
> > -     larl    %r13,\start
> > -     slgr    %r14,%r13
> > -     lghi    %r13,\end - \start
> > -     clgr    %r14,%r13
> > +     larl    %r14,\start
> > +     slgrk   %r14,\reg,%r14
> > +     clgfi   %r14,\end - \start
>
> Clever me.. slgrk was added with z196, and not z10.
> So dropping this patch.

How do the version numbers work for SystemZ? Is there a list/reference
you could link me to?  If it's too deep a rabbit hole, then nevermind,
but I would like to learn a little more about the architecture.
-- 
Thanks,
~Nick Desaulniers