Re: [PATCH v4] arm/virt: Add memory hot remove support

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 22 Jun 2020 13:41:57 +0100
Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> wrote:

> This adds support for memory(pc-dimm) hot remove on arm/virt that
> uses acpi ged device.
> 
> NVDIMM hot removal is not yet supported.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
> v2 --> v3
>   -Addressed Eric's comments on v3. 
> v2 --> v3
>   -Addressed Eric's review comment and added check for NVDIMM.
> RFC v1 --> v2
>   -Rebased on top of latest Qemu master.
>   -Dropped "RFC" and tested with kernel 5.7-rc6
> ---
>  hw/acpi/generic_event_device.c | 29 ++++++++++++++++
>  hw/arm/virt.c                  | 62 ++++++++++++++++++++++++++++++++--
>  2 files changed, 89 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/acpi/generic_event_device.c b/hw/acpi/generic_event_device.c
> index 1cb34111e5..b8abdefa1c 100644
> --- a/hw/acpi/generic_event_device.c
> +++ b/hw/acpi/generic_event_device.c
> @@ -193,6 +193,33 @@ static void acpi_ged_device_plug_cb(HotplugHandler *hotplug_dev,
>      }
>  }
>  
> +static void acpi_ged_unplug_request_cb(HotplugHandler *hotplug_dev,
> +                                       DeviceState *dev, Error **errp)
> +{
> +    AcpiGedState *s = ACPI_GED(hotplug_dev);
> +
> +    if ((object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) &&
> +                       !(object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM)))) {
> +        acpi_memory_unplug_request_cb(hotplug_dev, &s->memhp_state, dev, errp);
> +    } else {
> +        error_setg(errp, "acpi: device unplug request for unsupported device"
> +                   " type: %s", object_get_typename(OBJECT(dev)));
> +    }
> +}
> +
> +static void acpi_ged_unplug_cb(HotplugHandler *hotplug_dev,
> +                               DeviceState *dev, Error **errp)
> +{
> +    AcpiGedState *s = ACPI_GED(hotplug_dev);
> +
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        acpi_memory_unplug_cb(&s->memhp_state, dev, errp);
> +    } else {
> +        error_setg(errp, "acpi: device unplug for unsupported device"
> +                   " type: %s", object_get_typename(OBJECT(dev)));
> +    }
> +}
> +
>  static void acpi_ged_send_event(AcpiDeviceIf *adev, AcpiEventStatusBits ev)
>  {
>      AcpiGedState *s = ACPI_GED(adev);
> @@ -318,6 +345,8 @@ static void acpi_ged_class_init(ObjectClass *class, void *data)
>      dc->vmsd = &vmstate_acpi_ged;
>  
>      hc->plug = acpi_ged_device_plug_cb;
> +    hc->unplug_request = acpi_ged_unplug_request_cb;
> +    hc->unplug = acpi_ged_unplug_cb;
>  
>      adevc->send_event = acpi_ged_send_event;
>  }
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index caceb1e4a0..80ef2d7b7a 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2177,11 +2177,68 @@ static void virt_machine_device_plug_cb(HotplugHandler *hotplug_dev,
>      }
>  }
>  
> +static void virt_dimm_unplug_request(HotplugHandler *hotplug_dev,
> +                                     DeviceState *dev, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
> +    Error *local_err = NULL;
> +
> +    if (!vms->acpi_dev) {
> +        error_setg(&local_err,
> +                   "memory hotplug is not enabled: missing acpi-ged device");
> +        goto out;
> +    }
> +
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM)) {
> +        error_setg(&local_err,
> +                   "nvdimm device hot unplug is not supported yet.");
> +        goto out;
> +    }
> +
> +    hotplug_handler_unplug_request(HOTPLUG_HANDLER(vms->acpi_dev), dev,
> +                                   &local_err);
> +out:
> +    error_propagate(errp, local_err);
> +}
> +
> +static void virt_dimm_unplug(HotplugHandler *hotplug_dev,
> +                             DeviceState *dev, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
> +    Error *local_err = NULL;
> +
> +    hotplug_handler_unplug(HOTPLUG_HANDLER(vms->acpi_dev), dev, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    pc_dimm_unplug(PC_DIMM(dev), MACHINE(vms));
> +    qdev_unrealize(dev);

doesn't pc_dimm_unplug() do unrealize already?
(/me wonders why it doesn't explode here,
are we leaking a refference somewhere so dimm is still alive?)

> +
> +out:
> +    error_propagate(errp, local_err);
> +}
> +
>  static void virt_machine_device_unplug_request_cb(HotplugHandler *hotplug_dev,
>                                            DeviceState *dev, Error **errp)
>  {
> -    error_setg(errp, "device unplug request for unsupported device"
> -               " type: %s", object_get_typename(OBJECT(dev)));
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        virt_dimm_unplug_request(hotplug_dev, dev, errp);
> +    } else {
> +        error_setg(errp, "device unplug request for unsupported device"
> +                   " type: %s", object_get_typename(OBJECT(dev)));
> +    }
> +}
> +
> +static void virt_machine_device_unplug_cb(HotplugHandler *hotplug_dev,
> +                                          DeviceState *dev, Error **errp)
> +{
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        virt_dimm_unplug(hotplug_dev, dev, errp);
> +    } else {
> +        error_setg(errp, "virt: device unplug for unsupported device"
> +                   " type: %s", object_get_typename(OBJECT(dev)));
> +    }
>  }
>  
>  static HotplugHandler *virt_machine_get_hotplug_handler(MachineState *machine,
> @@ -2262,6 +2319,7 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
>      hc->pre_plug = virt_machine_device_pre_plug_cb;
>      hc->plug = virt_machine_device_plug_cb;
>      hc->unplug_request = virt_machine_device_unplug_request_cb;
> +    hc->unplug = virt_machine_device_unplug_cb;
>      mc->numa_mem_supported = true;
>      mc->nvdimm_supported = true;
>      mc->auto_enable_numa_with_memhp = true;