Re: [RFC PATCH v3 8/8] target/s390x: Use start-powered-off CPUState property

[Cornelia Huck]

On Wed, 22 Jul 2020 23:56:57 -0300
Thiago Jung Bauermann <bauerman@linux.ibm.com> wrote:

> Instead of setting CPUState::halted to 1 in s390_cpu_initfn(), use the
> start-powered-off property which makes cpu_common_reset() initialize it
> to 1 in common code.
> 
> Note that this changes behavior by setting cs->halted to 1 on reset, which
> didn't happen before.

I think that should be fine, as we change the cpu state to STOPPED in
the reset function, which sets halted to 1.

> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> ---
>  target/s390x/cpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> NB: I was only able to test that this patch builds. I wasn't able to
> run it.

No noticeable difference under kvm, but running under tcg seems a bit
more sluggish than usual, and I saw some pausing on reboot (after the
bios handover to the kernel). Not sure if it were just flukes on my
laptop, would appreciate if someone else could give it a go.

> 
> diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
> index 08eb674d22..73d7d6007e 100644
> --- a/target/s390x/cpu.c
> +++ b/target/s390x/cpu.c
> @@ -291,7 +291,7 @@ static void s390_cpu_initfn(Object *obj)
>      S390CPU *cpu = S390_CPU(obj);
>  
>      cpu_set_cpustate_pointers(cpu);
> -    cs->halted = 1;
> +    cs->start_powered_off = true;
>      cs->exception_index = EXCP_HLT;
>  #if !defined(CONFIG_USER_ONLY)
>      object_property_add(obj, "crash-information", "GuestPanicInformation",
>