Re: [Qemu-devel] [PATCH v3 4/6] target/s390x: Implement LOAD PAIR DISJOINT

[Aurelien Jarno <aurelien@aurel32.net>]

On 2017-05-10 10:43, Richard Henderson wrote:
> On 05/10/2017 10:13 AM, Éric Bischoff wrote:
> > Le mercredi 10 mai 2017, 12:16:20 Aurelien Jarno a écrit :
> > > > +    /* 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;
> > > > +    }
> > > 
> > > One small additional comment about this patch I haven't spotted at the
> > > first review. The exit_atomic helper is properly restoring the CPU state
> > > 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.
> > 
> > Merci pour la relecture Aurélien.
> > 
> > Richard, what do we do? We remove the potential_page_fault(s); or not?
> 
> 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.

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