Re: [PULL 00/30] ppc-for-5.2 queue 20200904

[Cornelia Huck]

On Mon, 7 Sep 2020 21:46:28 +0200
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> On 9/7/20 7:26 PM, Laurent Vivier wrote:
> > On 07/09/2020 18:29, Laurent Vivier wrote:  

> >> I think we should not enter in cpu_loop() with halted set to 1.
> >>
> >> Before the patch of this series, s390_cpu_reset() is called twice, and
> >> on the second call, halted is already 0.
> >>
> >> With start_powered_off set to true in initfn, on the first reset
> >> "halted" is 0 and on the second it is 1 (because it has been copied from
> >> start_powered_off) and so cpu_loop() starts with halted set to 1 and 
> >> fails.  
> > 
> > What is happening:
> > 
> > [without start_powered_off]
> > 
> >   1- halted is set to 1 in s390x_cpu_initfn()
> >   2- halted is set to 0 in s390x_cpu_reset() by parent_reset()
> >      (cpu_common_reset()
> >   3- cpu_loop() is always entered with halted set to 0
> > 
> > [with start_powered_off]
> > 
> >   1- halted is set to start_powered_off (1) in s390x_cpu_reset() by
> >      parent_reset() (cpu_common_reset()
> >   2- cpu_loop() is always entered with halted set to 1
> > 
> > So in the first case, cpu_loop() is always started with halted set to 0
> > and in the second case with halted set to 1.
> > 
> > And I think, with linux-user, it should never be started with halted set
> > to 1.

linux-user always confuses me a bit, but this seems right.

> > 
> > We can't add a "#ifdef CONFIG_USER_ONLY" in hw/core/cpu.c to set halted
> > to 0 because it is in the common files, but we can do:
> > 
> > diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
> > index 73d7d6007e8e..749cd548f0f3 100644
> > --- a/target/s390x/cpu.c
> > +++ b/target/s390x/cpu.c
> > @@ -291,9 +291,9 @@ static void s390_cpu_initfn(Object *obj)
> >      S390CPU *cpu = S390_CPU(obj);
> > 
> >      cpu_set_cpustate_pointers(cpu);
> > -    cs->start_powered_off = true;
> >      cs->exception_index = EXCP_HLT;
> >  #if !defined(CONFIG_USER_ONLY)
> > +    cs->start_powered_off = true;
> >      object_property_add(obj, "crash-information", "GuestPanicInformation",
> >                          s390_cpu_get_crash_info_qom, NULL, NULL, NULL);
> >      cpu->env.tod_timer =  
> 
> This looks like the correct fix indeed :)
> (Maybe worth adding a comment around).

Agreed on both counts.

> Thanks for investigating!

And here as well :)