Re: [Qemu-ppc] [Qemu-devel] [PATCH 1/2] spapr_cpu_core: instantiate CPUs separately

[Igor Mammedov]

On Fri, 13 Oct 2017 10:35:19 +0200
Greg Kurz <address@hidden> wrote:

> The current code assumes that only the CPU core object holds a
> reference on each individual CPU object, and happily frees their
> allocated memory when the core is unrealized. This is dangerous
> as some other code can legitimely keep a pointer to a CPU if it
> calls object_ref(), but it would end up with a dangling pointer.
> 
> Let's allocate all CPUs with object_new() and let QOM frees them
> when their reference count reaches zero.
I agree with patch as it simplifies code and one doesn't have to
fiddle wit size anymore.
See some comments below.

> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/ppc/spapr.c                  |   10 +++-------
>  hw/ppc/spapr_cpu_core.c         |   29 +++++++++--------------------
>  include/hw/ppc/spapr_cpu_core.h |    2 +-
>  3 files changed, 13 insertions(+), 28 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index fd9813bde82f..ba391c6ed5de 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -3153,12 +3153,10 @@ void spapr_core_release(DeviceState *dev)
>  
>      if (smc->pre_2_10_has_unused_icps) {
>          sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
> -        sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(cc));
> -        size_t size = object_type_get_instance_size(scc->cpu_type);
>          int i;
>  
>          for (i = 0; i < cc->nr_threads; i++) {
> -            CPUState *cs = CPU(sc->threads + i * size);
> +            CPUState *cs = CPU(sc->threads[i]);
>  
>              pre_2_10_vmstate_register_dummy_icp(cs->cpu_index);
>          }
> @@ -3204,7 +3202,7 @@ static void spapr_core_plug(HotplugHandler 
> *hotplug_dev, DeviceState *dev,
>      sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
>      sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
>      CPUCore *cc = CPU_CORE(dev);
> -    CPUState *cs = CPU(core->threads);
> +    CPUState *cs = CPU(core->threads[0]);
>      sPAPRDRConnector *drc;
>      Error *local_err = NULL;
>      int smt = kvmppc_smt_threads();
> @@ -3249,13 +3247,11 @@ static void spapr_core_plug(HotplugHandler 
> *hotplug_dev, DeviceState *dev,
>      core_slot->cpu = OBJECT(dev);
>  
>      if (smc->pre_2_10_has_unused_icps) {
> -        sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(cc));
> -        size_t size = object_type_get_instance_size(scc->cpu_type);
>          int i;
>  
>          for (i = 0; i < cc->nr_threads; i++) {
>              sPAPRCPUCore *sc = SPAPR_CPU_CORE(dev);
> -            void *obj = sc->threads + i * size;
> +            void *obj = sc->threads[i];
>  
>              cs = CPU(obj);
>              pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index);
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 3a4c17401226..47c408b52ca1 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -79,21 +79,18 @@ const char *spapr_get_cpu_core_type(const char *cpu_type)
>  static void spapr_cpu_core_unrealizefn(DeviceState *dev, Error **errp)
>  {
>      sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
> -    sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(dev));
> -    size_t size = object_type_get_instance_size(scc->cpu_type);
>      CPUCore *cc = CPU_CORE(dev);
>      int i;
>  
>      for (i = 0; i < cc->nr_threads; i++) {
> -        void *obj = sc->threads + i * size;
> -        DeviceState *dev = DEVICE(obj);
> +        DeviceState *dev = DEVICE(sc->threads[i]);
>          CPUState *cs = CPU(dev);
>          PowerPCCPU *cpu = POWERPC_CPU(cs);
>  
>          spapr_cpu_destroy(cpu);
>          object_unparent(cpu->intc);
>          cpu_remove_sync(cs);
> -        object_unparent(obj);
> +        object_unparent(sc->threads[i]);
>      }
>      g_free(sc->threads);
>  }
> @@ -146,9 +143,7 @@ static void spapr_cpu_core_realize(DeviceState *dev, 
> Error **errp)
>      sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
>      sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(dev));
>      CPUCore *cc = CPU_CORE(OBJECT(dev));
> -    size_t size;
>      Error *local_err = NULL;
> -    void *obj;
>      int i, j;
>  
>      if (!spapr) {
> @@ -156,17 +151,14 @@ static void spapr_cpu_core_realize(DeviceState *dev, 
> Error **errp)
>          return;
>      }
>  
> -    size = object_type_get_instance_size(scc->cpu_type);
> -    sc->threads = g_malloc0(size * cc->nr_threads);
> +    sc->threads = g_new(void *, cc->nr_threads);

                           ^^^ PowerPCCPU*

and maybe g_new0() if incomplete cores are possible.

>      for (i = 0; i < cc->nr_threads; i++) {
>          char id[32];
>          CPUState *cs;
>          PowerPCCPU *cpu;
>  
> -        obj = sc->threads + i * size;
> -
> -        object_initialize(obj, size, scc->cpu_type);
> -        cs = CPU(obj);
> +        sc->threads[i] = object_new(scc->cpu_type);
> +        cs = CPU(sc->threads[i]);
>          cpu = POWERPC_CPU(cs);
>          cs->cpu_index = cc->core_id + i;
>          cpu->vcpu_id = (cc->core_id * spapr->vsmt / smp_threads) + i;
> @@ -184,17 +176,15 @@ static void spapr_cpu_core_realize(DeviceState *dev, 
> Error **errp)
>          cpu->node_id = sc->node_id;
>  
>          snprintf(id, sizeof(id), "thread[%d]", i);
> -        object_property_add_child(OBJECT(sc), id, obj, &local_err);
> +        object_property_add_child(OBJECT(sc), id, sc->threads[i], 
> &local_err);
>          if (local_err) {
>              goto err;
>          }
> -        object_unref(obj);
> +        object_unref(sc->threads[i]);
>      }
>  
>      for (j = 0; j < cc->nr_threads; j++) {
> -        obj = sc->threads + j * size;
> -
> -        spapr_cpu_core_realize_child(obj, spapr, &local_err);
> +        spapr_cpu_core_realize_child(sc->threads[j], spapr, &local_err);
>          if (local_err) {
>              goto err;
>          }
> @@ -203,8 +193,7 @@ static void spapr_cpu_core_realize(DeviceState *dev, 
> Error **errp)
>  
>  err:
>      while (--i >= 0) {
> -        obj = sc->threads + i * size;
> -        object_unparent(obj);
> +        object_unparent(sc->threads[i]);
>      }
>      g_free(sc->threads);
>      error_propagate(errp, local_err);
> diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
> index f2d48d6a6786..f5b943a6682c 100644
> --- a/include/hw/ppc/spapr_cpu_core.h
> +++ b/include/hw/ppc/spapr_cpu_core.h
> @@ -28,7 +28,7 @@ typedef struct sPAPRCPUCore {
>      CPUCore parent_obj;
>  
>      /*< public >*/
> -    void *threads;
> +    void **threads;
ditto, should be PowerPCCPU

>      int node_id;
>  } sPAPRCPUCore;
>  
> 
>