Re: [Qemu-ppc] [Qemu-devel] [PATCH for-2.10 03/23] hw/arm/virt: use machine->possible_cpus for storing possible topology info

[Andrew Jones]

On Wed, Mar 22, 2017 at 02:32:28PM +0100, Igor Mammedov wrote:
> for now precalculate and store mp_afinity in possible_cpus
> as ARM cpus don't have socket/core/thread-id properties yet.
> In follow patches possible_cpus will be used for storing
> and setting NUMA node mapping and replace legacy bitmap
> based numa_info[node_id].node_cpu/numa_get_node_for_cpu()
> 
> For the lack of better idea, this patch cannibalizes
> possible_cpus.cpus[x].props.thread_id so that
> *_cpu_index_to_props() callback could return addressable
> by props CPU which will used by machine_set_cpu_numa_node()
> in follow up patches to assign a CPU to node. But
> cannibalizing is fine for now as that thread_id isn't exposed
> to users (no hotpluggable_cpus callback support for ARM yet)
> and it will be used only internally until 'device_add cpu'
> is supported where we can decide on which properties to use.
> 
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
>  hw/arm/virt.c | 39 ++++++++++++++++++++++++++++++++++++---
>  1 file changed, 36 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 484754e..4de46b1 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1237,6 +1237,7 @@ static void machvirt_init(MachineState *machine)
>  {
>      VirtMachineState *vms = VIRT_MACHINE(machine);
>      VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(machine);
> +    MachineClass *mc = MACHINE_GET_CLASS(machine);
>      qemu_irq pic[NUM_IRQS];
>      MemoryRegion *sysmem = get_system_memory();
>      MemoryRegion *secure_sysmem = NULL;
> @@ -1360,10 +1361,16 @@ static void machvirt_init(MachineState *machine)
>          exit(1);
>      }
>  
> -    for (n = 0; n < smp_cpus; n++) {
> -        Object *cpuobj = object_new(typename);
> +    mc->possible_cpu_arch_ids(machine);

Hmm, this is a bit too subtle for my taste. Making this call, which by
name implies it returns the possible CPU Arch-IDs (which indeed it does),
but without assigning its return value to anything, looks wrong. I see
the reason to do so, though, is because on first call it will do the
allocation. I'd prefer a wrapper

 static void virt_alloc_possible_cpus(MachineState *ms)
 {
    /* First invocation does allocation and initialization. */
    (void)MACHINE_GET_CLASS(ms)->possible_cpu_arch_ids(ms);
 }

> +    for (n = 0; n < machine->possible_cpus->len; n++) {
> +        Object *cpuobj;
>  
> -        object_property_set_int(cpuobj, virt_idx2mp_affinity(vms, n),
> +        if (n >= smp_cpus) {
> +            break;
> +        }
> +
> +        cpuobj = object_new(typename);
> +        object_property_set_int(cpuobj, 
> machine->possible_cpus->cpus[n].arch_id,
>                                  "mp-affinity", NULL);
>  
>          if (!vms->secure) {
> @@ -1543,6 +1550,31 @@ static void virt_set_gic_version(Object *obj, const 
> char *value, Error **errp)
>      }
>  }
>  
> +static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)
> +{
> +    int n;
> +    VirtMachineState *vms = VIRT_MACHINE(ms);
> +
> +    if (ms->possible_cpus) {
> +        assert(ms->possible_cpus->len == max_cpus);
> +        return ms->possible_cpus;
> +    }
> +
> +    ms->possible_cpus = g_malloc0(sizeof(CPUArchIdList) +
> +                                  sizeof(CPUArchId) * max_cpus);
> +    ms->possible_cpus->len = max_cpus;
> +    for (n = 0; n < ms->possible_cpus->len; n++) {
> +        ms->possible_cpus->cpus[n].arch_id =
> +            virt_idx2mp_affinity(vms, n);
> +        ms->possible_cpus->cpus[n].props.has_thread_id = true;
> +        ms->possible_cpus->cpus[n].props.thread_id = n;
> +
> +        /* TODO: add 'has_node/node' here to describe
> +           to which node core belongs */
> +    }
> +    return ms->possible_cpus;
> +}
> +
>  static void virt_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> @@ -1559,6 +1591,7 @@ static void virt_machine_class_init(ObjectClass *oc, 
> void *data)
>      mc->pci_allow_0_address = true;
>      /* We know we will never create a pre-ARMv7 CPU which needs 1K pages */
>      mc->minimum_page_bits = 12;
> +    mc->possible_cpu_arch_ids = virt_possible_cpu_arch_ids;
>  }
>  
>  static const TypeInfo virt_machine_info = {
> -- 
> 2.7.4
> 
> 

Thanks,
drew