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Date: Wed, 10 May 2017 20:24:38 +0200
From: Aurelien Jarno <aurelien@aurel32.net>
Message-ID: <20170510182438.rqj765wtbmun2i3u@aurel32.net>
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Subject: Re: [Qemu-devel] [PATCH v3 4/6] target/s390x: Implement LOAD PAIR
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To: Richard Henderson <rth@twiddle.net>
Cc: =?iso-8859-15?Q?=C9ric?= Bischoff <ebischoff@nerim.net>, qemu-devel@nongnu.org

On 2017-05-10 10:43, Richard Henderson wrote:
> On 05/10/2017 10:13 AM, =C9ric Bischoff wrote:
> > Le mercredi 10 mai 2017, 12:16:20 Aurelien Jarno a =E9crit :
> > > > +    /* In a parallel context, stop the world and single step.  */
> > > > +    if (parallel_cpus) {
> > > > +        potential_page_fault(s);
> > > > +        gen_helper_exit_atomic(cpu_env);
> > > > +        return EXIT_NORETURN;
> > > > +    }
> > >=20
> > > One small additional comment about this patch I haven't spotted at the
> > > first review. The exit_atomic helper is properly restoring the CPU st=
ate
> > > passing the return address to cpu_loop_exit_atomic, so I believe the
> > > potential_page_fault call is not necessary. That said, it doesn't hurt
> > > either.
> >=20
> > Merci pour la relecture Aur=E9lien.
> >=20
> > Richard, what do we do? We remove the potential_page_fault(s); or not?
>=20
> I'm thinking of using gen_exception(EXCP_ATOMIC) instead.
> The unwind associated with the regular helper_exit_atomic
> has more overhead than potential_page_fault().

That was just a remark to optimize the code a bit. That said I think the
current code can go like that, it is not wrong.

--=20
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net