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Date: Mon, 17 Sep 2018 18:39:10 +1000
From: Nicholas Piggin <npiggin@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 03/12] powerpc/64s/hash: move POWER5 < DD2.1 slbie
 workaround where it is needed
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On Mon, 17 Sep 2018 11:30:16 +0530
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote:

> Nicholas Piggin <npiggin@gmail.com> writes:
> 
> > The POWER5 < DD2.1 issue is that slbie needs to be issued more than
> > once. It came in with this change:
> >
> > ChangeSet@1.1608, 2004-04-29 07:12:31-07:00, david@gibson.dropbear.id.au
> >   [PATCH] POWER5 erratum workaround
> >
> >   Early POWER5 revisions (<DD2.1) have a problem requiring slbie
> >   instructions to be repeated under some circumstances.  The patch below
> >   adds a workaround (patch made by Anton Blanchard).  
> 
> Thanks for extracting this. Can we add this to the code?

The comment? Sure.

> Also I am not
> sure what is repeated here? Is it that we just need one slb extra(hence
> only applicable to offset == 1) or is it that we need to make sure there
> is always one slb extra? The code does the former.

Yeah it has always done the former, so my assumption is that you just
need more than one slbie. I don't think we need to bother revisiting
that assumption unless someone can pull up something definitive.

What I did change is that slbia no longer has the additional slbie, but
I think there are strong reasons not to need that.

>  Do you a have link for
> that email patch?

I tried looking through the archives around that date but could not
find it. That came from a bitkeeper log.

Thanks,
Nick