Re: [PATCH v4 6/6] hw/loongarch/virt: Enable cpu hotplug feature on virt machine

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 12 Nov 2024 10:17:38 +0800
Bibo Mao <maobibo@loongson.cn> wrote:

> On virt machine, enable CPU hotplug feature has_hotpluggable_cpus. For
> hot-added CPUs, there is socket-id/core-id/thread-id property set,
> arch_id can be caculated from these properties. So that cpu slot can be
> searched from its arch_id.
> 
> Also change num-cpu property of extioi and ipi from smp.cpus to
> smp.max_cpus
> 
> Co-developed-by: Xianglai Li <lixianglai@loongson.cn>
> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> ---
>  hw/loongarch/virt.c | 68 +++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 59 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
> index b49b15c0f6..5f81673368 100644
> --- a/hw/loongarch/virt.c
> +++ b/hw/loongarch/virt.c
> @@ -890,7 +890,7 @@ static void virt_irq_init(LoongArchVirtMachineState *lvms)
>  
>      /* Create IPI device */
>      ipi = qdev_new(TYPE_LOONGARCH_IPI);
> -    qdev_prop_set_uint32(ipi, "num-cpu", ms->smp.cpus);
> +    qdev_prop_set_uint32(ipi, "num-cpu", ms->smp.max_cpus);
>      sysbus_realize_and_unref(SYS_BUS_DEVICE(ipi), &error_fatal);
>      lvms->ipi = ipi;
>  
> @@ -905,7 +905,7 @@ static void virt_irq_init(LoongArchVirtMachineState *lvms)
>  
>      /* Create EXTIOI device */
>      extioi = qdev_new(TYPE_LOONGARCH_EXTIOI);
> -    qdev_prop_set_uint32(extioi, "num-cpu", ms->smp.cpus);
> +    qdev_prop_set_uint32(extioi, "num-cpu", ms->smp.max_cpus);
>      if (virt_is_veiointc_enabled(lvms)) {
>          qdev_prop_set_bit(extioi, "has-virtualization-extension", true);
>      }
> @@ -1369,11 +1369,15 @@ static void virt_get_topo_from_index(MachineState *ms,
>  }
>  
>  /* Find cpu slot in machine->possible_cpus by arch_id */
> -static CPUArchId *virt_find_cpu_slot(MachineState *ms, int arch_id)
> +static CPUArchId *virt_find_cpu_slot(MachineState *ms, int arch_id, int *index)
>  {
>      int n;
>      for (n = 0; n < ms->possible_cpus->len; n++) {
>          if (ms->possible_cpus->cpus[n].arch_id == arch_id) {
> +            if (index) {
> +                *index = n;
> +            }
> +
>              return &ms->possible_cpus->cpus[n];
>          }
>      }
> @@ -1386,10 +1390,12 @@ static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev,
>  {
>      LoongArchVirtMachineState *lvms = LOONGARCH_VIRT_MACHINE(hotplug_dev);
>      MachineState *ms = MACHINE(OBJECT(hotplug_dev));
> +    CPUState *cs = CPU(dev);
>      LoongArchCPU *cpu = LOONGARCH_CPU(dev);
>      CPUArchId *cpu_slot;
>      Error *local_err = NULL;
> -    int arch_id;
> +    LoongArchCPUTopo topo;
> +    int arch_id, index;
>  
>      /* sanity check the cpu */
>      if (!object_dynamic_cast(OBJECT(cpu), ms->cpu_type)) {
> @@ -1408,12 +1414,45 @@ static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev,
>       }
>  
>      if (cpu->phy_id == UNSET_PHY_ID) {

> -        error_setg(&local_err, "CPU hotplug not supported");
> -        goto out;
> +        if ((cpu->thread_id < 0) || (cpu->thread_id >= ms->smp.threads)) {
> +            error_setg(&local_err,
> +                       "Invalid thread-id %u specified, must be in range 1:%u",
> +                       cpu->thread_id, ms->smp.threads - 1);
> +            goto out;
> +        }
> +
> +        if ((cpu->core_id < 0) || (cpu->core_id >= ms->smp.cores)) {
> +            error_setg(&local_err,
> +                       "Invalid core-id %u specified, must be in range 1:%u",
> +                       cpu->core_id, ms->smp.cores - 1);
> +            goto out;
> +        }
> +
> +        if ((cpu->socket_id < 0) || (cpu->socket_id >= ms->smp.sockets)) {
> +            error_setg(&local_err,
> +                       "Invalid socket-id %u specified, must be in range 1:%u",
> +                       cpu->socket_id, ms->smp.sockets - 1);
> +            goto out;
> +        }
> +
> +        topo.socket_id = cpu->socket_id;
> +        topo.core_id = cpu->core_id;
> +        topo.thread_id = cpu->thread_id;
> +        arch_id =  virt_get_arch_id_from_topo(ms, &topo);
> +        cpu_slot = virt_find_cpu_slot(ms, arch_id, &index);
> +        if (CPU(cpu_slot->cpu)) {
> +            error_setg(&local_err,
> +                       "cpu(id%d=%d:%d:%d) with arch-id %" PRIu64 " exists",
> +                       cs->cpu_index, cpu->socket_id, cpu->core_id,
> +                       cpu->thread_id, cpu_slot->arch_id);
> +            goto out;
> +        }
> +        cpu->phy_id = arch_id;
> +        cs->cpu_index = index;
this whole branch applies to cold-plugged CPUs as well, especially
if both (hot/cold plugged CPUs are getting wired with help of pre_plug)
So this hunk should be introduced somewhere earlier in series,
and than I'd likely won't need (cpu->phy_id == UNSET_PHY_ID) check to begin with.

the only difference vs cold-plug would be need to call acpi_ged plug handler,
like you are dong below in virt_cpu_plug

>      } else {
>          /* For cold-add cpu, find cpu slot from arch_id */
>          arch_id = cpu->phy_id;
> -        cpu_slot = virt_find_cpu_slot(ms, arch_id);
> +        cpu_slot = virt_find_cpu_slot(ms, arch_id, NULL);
>      }
>  
>      numa_cpu_pre_plug(cpu_slot, dev, &local_err);
> @@ -1468,7 +1507,7 @@ static void virt_cpu_unplug(HotplugHandler *hotplug_dev,
>          return;
>      }
>  
> -    cpu_slot = virt_find_cpu_slot(MACHINE(lvms), cpu->phy_id);
> +    cpu_slot = virt_find_cpu_slot(MACHINE(lvms), cpu->phy_id, NULL);
>      cpu_slot->cpu = NULL;
>      return;
>  }
> @@ -1477,14 +1516,24 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev,
>                                  DeviceState *dev, Error **errp)
>  {
>      CPUArchId *cpu_slot;
> +    Error *local_err = NULL;
>      LoongArchCPU *cpu = LOONGARCH_CPU(dev);
>      MachineState *ms = MACHINE(hotplug_dev);
>      LoongArchVirtMachineState *lvms = LOONGARCH_VIRT_MACHINE(hotplug_dev);
>  
>      /* Connect irq to cpu, including ipi and extioi irqchip */
>      virt_init_cpu_irq(ms, CPU(cpu));
> -    cpu_slot = virt_find_cpu_slot(MACHINE(lvms), cpu->phy_id);
> +    cpu_slot = virt_find_cpu_slot(MACHINE(lvms), cpu->phy_id, NULL);
>      cpu_slot->cpu = CPU(dev);
> +
> +    if (lvms->acpi_ged) {
Why do you need check, can machine be created without acpi_ged?

> +        hotplug_handler_plug(HOTPLUG_HANDLER(lvms->acpi_ged), dev, &local_err);
> +        if (local_err) {
> +            error_propagate(errp, local_err);
> +            return;
> +        }
> +    }
> +
>      return;
>  }
>  
> @@ -1667,6 +1716,7 @@ static void virt_class_init(ObjectClass *oc, void *data)
>      mc->numa_mem_supported = true;
>      mc->auto_enable_numa_with_memhp = true;
>      mc->auto_enable_numa_with_memdev = true;
> +    mc->has_hotpluggable_cpus = true;
>      mc->get_hotplug_handler = virt_get_hotplug_handler;
>      mc->default_nic = "virtio-net-pci";
>      hc->plug = virt_device_plug_cb;