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

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Date:   Thu, 12 May 2022 21:15:00 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Nick Desaulniers <ndesaulniers@...gle.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 11:00:31AM -0700, Nick Desaulniers wrote:
> 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.

If it is only for the machine generations the following links might help:

https://www.ibm.com/support/pages/ibm-mainframe-life-cycle-history
(see linked pdf for list of machine names)

https://en.wikipedia.org/wiki/IBM_Z

There might be better sources, but that's all I could find right now.