Re: [Qemu-devel] hw/s390x/ipl: Dubious use of qdev_reset_all_fn

[Christian Borntraeger]

On 24.05.19 21:00, David Hildenbrand wrote:
> On 24.05.19 20:36, David Hildenbrand wrote:
>> On 24.05.19 20:28, Christian Borntraeger wrote:
>>>
>>>
>>> On 24.05.19 20:04, David Hildenbrand wrote:
>>>> On 24.05.19 19:54, Philippe Mathieu-Daudé wrote:
>>>>> Hi Christian,
>>>>>
>>>>> I'm having hard time to understand why the S390_IPL object calls
>>>>> qemu_register_reset(qdev_reset_all_fn) in its realize() method, while
>>>>> being QOM'ified (it has a reset method).
>>>>>
>>>>> It doesn't seem to have a qdev children added explicitly to it.
>>>>> I see it is used as a singleton, what else am I missing?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Phil.
>>>>>
>>>>
>>>> Looks like I added it back then (~4 years ago) when converting it into a
>>>> TYPE_DEVICE.
>>>>
>>>> I could imagine that - back then - this was needed because only
>>>> TYPE_SYS_BUS_DEVICE would recursively get reset.
>>>
>>> Yes, back then singleton devices were not recursively resetted. Has that 
>>> changed?
>>
>> Hacking that call out, I don't see it getting called anymore. So it is
>> still required. The question is if it can be reworked.
>>
> 
> Yes, as it is not a sysbus device, it won't get reset.
> The owner (machine) has to take care of this. The following works:
> 
> 
> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> index b93750c14e..91a31c2cd0 100644
> --- a/hw/s390x/ipl.c
> +++ b/hw/s390x/ipl.c
> @@ -232,7 +232,6 @@ static void s390_ipl_realize(DeviceState *dev, Error 
> **errp)
>       */
>      ipl->compat_start_addr = ipl->start_addr;
>      ipl->compat_bios_start_addr = ipl->bios_start_addr;
> -    qemu_register_reset(qdev_reset_all_fn, dev);
>  error:
>      error_propagate(errp, err);
>  }
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index bbc6e8fa0b..658ab529a1 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -338,6 +338,11 @@ static inline void s390_do_cpu_ipl(CPUState *cs, 
> run_on_cpu_data arg)
>      s390_cpu_set_state(S390_CPU_STATE_OPERATING, cpu);
>  }
>  
> +static void s390_ipl_reset(void)
> +{
> +    qdev_reset_all(DEVICE(object_resolve_path_type("", TYPE_S390_IPL, 
> NULL)));
> +}
> +
>  static void s390_machine_reset(void)
>  {
>      enum s390_reset reset_type;
> @@ -353,6 +358,7 @@ static void s390_machine_reset(void)
>      case S390_RESET_EXTERNAL:
>      case S390_RESET_REIPL:
>          qemu_devices_reset();
> +        s390_ipl_reset();
>          s390_crypto_reset();
>  
>          /* configure and start the ipl CPU only */
> 

While this patch is certainly ok, I find it disturbing that qdev devices are 
being resetted,
but qom devices not.