Re: [PATCH] hw/core: Fix data type in do_nmi()

[Greg Kurz]

On Fri,  6 Dec 2019 17:36:42 +1100
Gavin Shan <address@hidden> wrote:

> object_dynamic_cast() should return machine (or GPIO) state instad of NMI
> state in do_nmi(). So it's wrong to convert it to NMI state unconditionally.
> 

object_dynamic_cast() returns either its first argument if it can be cast
to the given typename or NULL. Since the x86, ccw and spapr machines and
the PowerMac GPIO implement the NMI interface, nothing is wrong here.

The do_nmi() function is called for all objects in the QOM tree and simply
filters out the ones that don't implement the NMI interface.

I do agree that this isn't super obvious though. It would be clearer to
do the filtering in the foreach() function. Something like:

https://patchwork.ozlabs.org/patch/1182232/

> This changes the prototype of NMIClass::nmi_monitor_handler() to accept
> the parent object of NMI state instead of itself. With this, he parent object
> is passed to the function, to avoid potential data corruption.
> 
> Signed-off-by: Gavin Shan <address@hidden>
> ---
>  hw/core/nmi.c              | 8 ++++----
>  hw/i386/x86.c              | 2 +-
>  hw/misc/macio/gpio.c       | 6 +++---
>  hw/ppc/spapr.c             | 2 +-
>  hw/s390x/s390-virtio-ccw.c | 2 +-
>  include/hw/nmi.h           | 2 +-
>  6 files changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/core/nmi.c b/hw/core/nmi.c
> index 481c4b3c7e..554708d0db 100644
> --- a/hw/core/nmi.c
> +++ b/hw/core/nmi.c
> @@ -37,13 +37,13 @@ static void nmi_children(Object *o, struct do_nmi_s *ns);
>  static int do_nmi(Object *o, void *opaque)
>  {
>      struct do_nmi_s *ns = opaque;
> -    NMIState *n = (NMIState *) object_dynamic_cast(o, TYPE_NMI);
> +    Object *parent = object_dynamic_cast(o, TYPE_NMI);
>  
> -    if (n) {
> -        NMIClass *nc = NMI_GET_CLASS(n);
> +    if (parent) {
> +        NMIClass *nc = NMI_GET_CLASS(parent);
>  
>          ns->handled = true;
> -        nc->nmi_monitor_handler(n, ns->cpu_index, &ns->err);
> +        nc->nmi_monitor_handler(parent, ns->cpu_index, &ns->err);
>          if (ns->err) {
>              return -1;
>          }
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index 394edc2f72..b98204f104 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -190,7 +190,7 @@ const CPUArchIdList 
> *x86_possible_cpu_arch_ids(MachineState *ms)
>      return ms->possible_cpus;
>  }
>  
> -static void x86_nmi(NMIState *n, int cpu_index, Error **errp)
> +static void x86_nmi(Object *parent, int cpu_index, Error **errp)
>  {
>      /* cpu index isn't used */
>      CPUState *cs;
> diff --git a/hw/misc/macio/gpio.c b/hw/misc/macio/gpio.c
> index 6cca6b27d6..6b4dfcc188 100644
> --- a/hw/misc/macio/gpio.c
> +++ b/hw/misc/macio/gpio.c
> @@ -196,10 +196,10 @@ static void macio_gpio_reset(DeviceState *dev)
>      macio_set_gpio(s, 1, true);
>  }
>  
> -static void macio_gpio_nmi(NMIState *n, int cpu_index, Error **errp)
> +static void macio_gpio_nmi(Object *parent, int cpu_index, Error **errp)
>  {
> -    macio_set_gpio(MACIO_GPIO(n), 9, true);
> -    macio_set_gpio(MACIO_GPIO(n), 9, false);
> +    macio_set_gpio(MACIO_GPIO(parent), 9, true);
> +    macio_set_gpio(MACIO_GPIO(parent), 9, false);
>  }
>  
>  static void macio_gpio_class_init(ObjectClass *oc, void *data)
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e076f6023c..3b92e4013d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -3377,7 +3377,7 @@ void spapr_do_system_reset_on_cpu(CPUState *cs, 
> run_on_cpu_data arg)
>      ppc_cpu_do_system_reset(cs);
>  }
>  
> -static void spapr_nmi(NMIState *n, int cpu_index, Error **errp)
> +static void spapr_nmi(Object *parent, int cpu_index, Error **errp)
>  {
>      CPUState *cs;
>  
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index d3edeef0ad..a49952a8b9 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -431,7 +431,7 @@ static void s390_hot_add_cpu(MachineState *machine,
>      s390x_new_cpu(object_class_get_name(oc), id, errp);
>  }
>  
> -static void s390_nmi(NMIState *n, int cpu_index, Error **errp)
> +static void s390_nmi(Object *parent, int cpu_index, Error **errp)
>  {
>      CPUState *cs = qemu_get_cpu(cpu_index);
>  
> diff --git a/include/hw/nmi.h b/include/hw/nmi.h
> index a1e128724e..75afa67790 100644
> --- a/include/hw/nmi.h
> +++ b/include/hw/nmi.h
> @@ -38,7 +38,7 @@ typedef struct NMIState NMIState;
>  typedef struct NMIClass {
>      InterfaceClass parent_class;
>  
> -    void (*nmi_monitor_handler)(NMIState *n, int cpu_index, Error **errp);
> +    void (*nmi_monitor_handler)(Object *parent, int cpu_index, Error **errp);
>  } NMIClass;
>  
>  void nmi_monitor_handle(int cpu_index, Error **errp);