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

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 24 Jun 2020 16:50:11 +0000
Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> wrote:

> > -----Original Message-----
> > From: Igor Mammedov [mailto:imammedo@redhat.com]
> > Sent: 24 June 2020 15:09
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> > Cc: qemu-devel@nongnu.org; qemu-arm@nongnu.org;
> > peter.maydell@linaro.org; mst@redhat.com; Linuxarm
> > <linuxarm@huawei.com>; xuwei (O) <xuwei5@huawei.com>;
> > eric.auger@redhat.com; Zengtao (B) <prime.zeng@hisilicon.com>
> > Subject: Re: [PATCH v4] arm/virt: Add memory hot remove support
> > 
> > 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  
> 
> [...]
> 
> > > +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?)  
> 
> Does it? From a quick look at the code it is not obvious.
> 
> pc_dimm_unplug()
>   memory_device_unplug()
>     memory_region_del_subregion()
>   vmstate_unregister_ram()
>     qemu_ram_unset_idstr()
>     qemu_ram_unset_migratable()
> 
> If it does, then we may need to fix x86/ppc as well.
you are right, it's correct.
I mixed it up with:
 pc_memory_unplug()
     pc_dimm_unplug(PC_DIMM(dev), MACHINE(pcms));
     object_property_set_bool(OBJECT(dev), false, "realized", &error_abort);


> 
> Thanks,
> Shameer
> 
> > > +
> > > +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;  
>