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Date: Tue, 19 Jun 2018 07:28:11 -0700
From: Ram Pai <linuxram@us.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, dave.hansen@intel.com,
 aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com,
 hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com,
 Ulrich.Weigand@de.ibm.com, fweimer@redhat.com, luto@kernel.org,
 msuchanek@suse.de
Subject: Re: [PATCH v2 2/6] powerpc/pkeys: Save the pkey registers before fork
Reply-To: Ram Pai <linuxram@us.ibm.com>
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On Tue, Jun 19, 2018 at 10:39:56PM +1000, Michael Ellerman wrote:
> Ram Pai <linuxram@us.ibm.com> writes:
> 
> > When a thread forks the contents of AMR, IAMR, UAMOR registers in the
> > newly forked thread are not inherited.
> >
> > Save the registers before forking, for content of those
> > registers to be automatically copied into the new thread.
> >
> > CC: Michael Ellerman <mpe@ellerman.id.au>
> > CC: Florian Weimer <fweimer@redhat.com>
> > CC: Andy Lutomirski <luto@kernel.org>
> > CC: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> > Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> 
> Again this is an ABI change but we'll call it a bug fix I guess.

yes. the same defense here too. its a behaviorial change for the better.
Single threaded applications will not see any behaviorial change.
Multithreaded apps, which were unable to consume, the behavior will now be
able to do so.

> 
> I'll add:
> 
>   Fixes: cf43d3b26452 ("powerpc: Enable pkey subsystem")
>   Cc: stable@vger.kernel.org # v4.16+

yes.  Thanks
RP