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Date: Fri, 15 Jul 2022 14:59:51 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Tulio Magno Quites Machado Filho <tuliom@ascii.art.br>
Cc: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org,
 Florian Weimer <fweimer@redhat.com>, gcc@gcc.gnu.org,
 libc-alpha@sourceware.org, Paul E Murphy <murphyp@linux.ibm.com>
Subject: Re: [PATCH v2] powerpc: add documentation for HWCAPs
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On Fri, Jul 15, 2022 at 03:41:20PM -0300, Tulio Magno Quites Machado Filho wrote:
> Nicholas Piggin <npiggin@gmail.com> writes:
> 
> > +PPC_FEATURE_ARCH_2_05
> > +    The processor supports the v2.05 userlevel architecture. Processors
> > +    supporting later architectures also set this feature.
> 
> I don't think this bit is enabled when processors support later architectures.
> In my tests, this behavior started only with v2.06, i.e. processors that
> support v2.07 enable bit v2.06, but do not enable bit v2.05.

That is a usability problem.  Can it be fixed, or will that create its
own compatibility problems?  In practice I mean.  If it is, the C
libraries could fix it up, for new programs, and then after a while the
kernel can do the sane thing?

How big is the problem, anyway?  Is it only 2.05, or also 2.04, 2.03?


Segher