Re: [Qemu-devel] [PATCH 11/11] spapr: Memory hot-unplug support

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Wed, Oct 12, 2016 at 06:13:59PM -0500, Michael Roth wrote:
> From: Bharata B Rao <bharata@linux.vnet.ibm.com>
> 
> Add support to hot remove pc-dimm memory devices.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> * add hooks to CAS/cmdline enablement of hotplug ACR support
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c     | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  hw/ppc/spapr_drc.c |  17 +++++++++
>  2 files changed, 122 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 9af4268..180fa3d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2310,6 +2310,90 @@ out:
>      error_propagate(errp, local_err);
>  }
> 
> +typedef struct sPAPRDIMMState {
> +    uint32_t nr_lmbs;
> +} sPAPRDIMMState;
> +
> +static void spapr_lmb_release(DeviceState *dev, void *opaque)
> +{
> +    sPAPRDIMMState *ds = (sPAPRDIMMState *)opaque;
> +    HotplugHandler *hotplug_ctrl = NULL;
> +
> +    if (--ds->nr_lmbs) {
> +        return;
> +    }
> +
> +    g_free(ds);
> +
> +    /*
> +     * Now that all the LMBs have been removed by the guest, call the
> +     * pc-dimm unplug handler to cleanup up the pc-dimm device.
> +     */
> +    hotplug_ctrl = qdev_get_hotplug_handler(dev);
> +    hotplug_handler_unplug(hotplug_ctrl, dev, &error_abort);
> +}
> +
> +static void spapr_del_lmbs(DeviceState *dev, uint64_t addr_start, uint64_t size,
> +                           Error **errp)
> +{
> +    sPAPRDRConnector *drc;
> +    sPAPRDRConnectorClass *drck;
> +    uint32_t nr_lmbs = size / SPAPR_MEMORY_BLOCK_SIZE;
> +    int i;
> +    sPAPRDIMMState *ds = g_malloc0(sizeof(sPAPRDIMMState));
> +    uint64_t addr = addr_start;
> +
> +    ds->nr_lmbs = nr_lmbs;
> +    for (i = 0; i < nr_lmbs; i++) {
> +        drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
> +                addr / SPAPR_MEMORY_BLOCK_SIZE);
> +        g_assert(drc);
> +
> +        drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> +        drck->detach(drc, dev, spapr_lmb_release, ds, errp);
> +        addr += SPAPR_MEMORY_BLOCK_SIZE;
> +    }
> +
> +    drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
> +                                   addr_start / SPAPR_MEMORY_BLOCK_SIZE);
> +    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> +    spapr_hotplug_req_remove_by_count_indexed(SPAPR_DR_CONNECTOR_TYPE_LMB,
> +                                              nr_lmbs,
> +                                              drck->get_index(drc));
> +}
> +
> +static void spapr_memory_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
> +                                Error **errp)
> +{
> +    sPAPRMachineState *ms = SPAPR_MACHINE(hotplug_dev);
> +    PCDIMMDevice *dimm = PC_DIMM(dev);
> +    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> +    MemoryRegion *mr = ddc->get_memory_region(dimm);
> +
> +    pc_dimm_memory_unplug(dev, &ms->hotplug_memory, mr);
> +    object_unparent(OBJECT(dev));
> +}
> +
> +static void spapr_memory_unplug_request(HotplugHandler *hotplug_dev,
> +                                        DeviceState *dev, Error **errp)
> +{
> +    Error *local_err = NULL;
> +    PCDIMMDevice *dimm = PC_DIMM(dev);
> +    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> +    MemoryRegion *mr = ddc->get_memory_region(dimm);
> +    uint64_t size = memory_region_size(mr);
> +    uint64_t addr;
> +
> +    addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    spapr_del_lmbs(dev, addr, size, &error_abort);
> +out:
> +    error_propagate(errp, local_err);
> +}
> +
>  void *spapr_populate_hotplug_cpu_dt(CPUState *cs, int *fdt_offset,
>                                      sPAPRMachineState *spapr)
>  {
> @@ -2383,10 +2467,21 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>  static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev,
>                                        DeviceState *dev, Error **errp)
>  {
> +    sPAPRMachineState *sms = SPAPR_MACHINE(qdev_get_machine());
>      MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
> 
>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> -        error_setg(errp, "Memory hot unplug not supported by sPAPR");
> +        if (spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT)) {
> +            spapr_memory_unplug(hotplug_dev, dev, errp);
> +        } else {
> +            /* NOTE: this means there is a window after guest reset, prior to
> +             * CAS negotiation, where unplug requests will fail due to the
> +             * capability not being detected yet. This is a bit different than
> +             * the case with PCI unplug, where the events will be queued and
> +             * eventually handled by the guest after boot
> +             */
> +            error_setg(errp, "Memory hot unplug not supported for this guest");
> +        }
>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
>          if (!mc->query_hotpluggable_cpus) {
>              error_setg(errp, "CPU hot unplug not supported on this machine");
> @@ -2396,6 +2491,14 @@ static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev,
>      }
>  }
> 
> +static void spapr_machine_device_unplug_request(HotplugHandler *hotplug_dev,
> +                                                DeviceState *dev, Error **errp)
> +{
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        spapr_memory_unplug_request(hotplug_dev, dev, errp);
> +    }
> +}
> +
>  static void spapr_machine_device_pre_plug(HotplugHandler *hotplug_dev,
>                                            DeviceState *dev, Error **errp)
>  {
> @@ -2482,6 +2585,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      hc->plug = spapr_machine_device_plug;
>      hc->unplug = spapr_machine_device_unplug;
>      mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
> +    hc->unplug_request = spapr_machine_device_unplug_request;

After this, spapr_core_unplug() call needs to be moved to
->unplug_request() as ->unplug() won't be called if ->unplug_request()
is present.

However I am not able to get CPU hotplug working with your patchset.
Looks like RTAS event is getting missed or not getting generated. Will
get back after further debugging.

Regards,
Bharata.