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Date:   Fri, 12 Mar 2021 11:00:10 +1000
From:   Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v2 36/43] powerpc/32: Set current->thread.regs in C
 interrupt entry
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Paul Mackerras <paulus@samba.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <cover.1615291471.git.christophe.leroy@csgroup.eu>
        <8d523f9ecee1de0515cc31d43030c12ab171a670.1615291474.git.christophe.leroy@csgroup.eu>
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        <035298ad-4d0b-5e74-6f5c-e03677580924@csgroup.eu>
        <5a80e05e-27d7-0e95-67c7-0fe3255c4be1@csgroup.eu>
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Excerpts from Christophe Leroy's message of March 11, 2021 10:38 pm:
>=20
>=20
> Le 11/03/2021 =C3=A0 11:38, Christophe Leroy a =C3=A9crit=C2=A0:
>>=20
>>=20
>> Le 10/03/2021 =C3=A0 02:33, Nicholas Piggin a =C3=A9crit=C2=A0:
>>> Excerpts from Christophe Leroy's message of March 9, 2021 10:10 pm:
>>>> No need to do that is assembly, do it in C.
>>>
>>> Hmm. No issues with the patch as such, but why does ppc32 need this but
>>> not 64? AFAIKS 64 sets this when a thread is created.
>>=20
>> Looks like ppc64 was doing the same in function save_remaining_regs() in=
 arch/ppc64/kernel/head.S=20
>> until commit https://github.com/mpe/linux-fullhistory/commit/e5bb080d
>>=20
>> But I can't find what happend to it in that commit.
>>=20
>> Where is it done now ? Maybe that's also already done for ppc32.
>>=20
>=20
> I digged a bit more and found a later bug fix which adds that setting of =
current->thread.regs at=20
> task creation: https://github.com/mpe/linux-fullhistory/commit/3eac1897
>=20
> That was in the ppc64 tree only at that time, and was merged into the com=
mon powerpc tree via commit=20
> https://github.com/mpe/linux-fullhistory/commit/06d67d54

Nice archaeology!

> So we have it for both ppc32 and ppc64 and ppc32 doesn't need to do it at=
 exception entry anymore.=20
> I'll remove it.

Good, that's what I hoped (otherwise ppc64 would have been missing=20
something).

Thanks,
Nick