RE: [PATCH v2] arm/virt: Add memory hot remove support

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

Hi Eric,

> -----Original Message-----
> From: Auger Eric [mailto:eric.auger@redhat.com]
> Sent: 17 June 2020 14:54
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> qemu-devel@nongnu.org; qemu-arm@nongnu.org
> Cc: imammedo@redhat.com; peter.maydell@linaro.org; mst@redhat.com;
> xuwei (O) <xuwei5@huawei.com>; Zengtao (B) <prime.zeng@hisilicon.com>;
> Linuxarm <linuxarm@huawei.com>
> Subject: Re: [PATCH v2] arm/virt: Add memory hot remove support
> 
> Hi Shameer,
> 
> On 5/20/20 1:03 PM, Shameer Kolothum wrote:
> > This adds support for memory hot remove on arm/virt that
> > uses acpi ged device.
> >
> > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> > ---
> > 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 | 28 +++++++++++++++++
> >  hw/arm/virt.c                  | 56
> ++++++++++++++++++++++++++++++++--
> >  2 files changed, 82 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/acpi/generic_event_device.c
> b/hw/acpi/generic_event_device.c
> > index b1cbdd86b6..2b3bedcd2f 100644
> > --- a/hw/acpi/generic_event_device.c
> > +++ b/hw/acpi/generic_event_device.c
> > @@ -193,6 +193,32 @@ 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)) {
> > +        acpi_memory_unplug_request_cb(hotplug_dev,
> &s->memhp_state, dev, errp);
> is it allowed to unplug NVDIMM? As NVDIMM inherits from PCDIMM, I wonder
> if we have to handle the case differently (as done in hotplug part).

True. This patch requires NVDMM check. I think when I sent out the initial RFC
NVDIMM hot add was not merged and I forgot to update it. My bad.

But not sure we need to add the check here if we take care that in
virt_machine_device_unplug_request_cb() as you have noted below. Do we?
 
> > +    } 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 +344,8 @@ 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 37462a6f78..110fa73990 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -2177,11 +2177,62 @@ 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(errp,
> > +                   "memory hotplug is not enabled: missing acpi-ged
> device");
> > +        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));
> > +    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
> > +
> > + 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)) {
> same here. By comparison, in hw/i386/pc.c, it is said
> "nvdimm device hot unplug is not supported yet."

Sure. I will change it.

> what is the situation on ARM?

I don’t think it supports it. I will check.

Thanks,
Shameer
 
> Thanks
> 
> Eric
> > +        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 +2313,7 @@ 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;
> >