Re: [Qemu-devel] [RFC PATCH v0 3/3] spapr: Memory hot-unplug support

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Bharata B Rao (2015-08-19 01:56:11)
> Add support to hot remove pc-dimm memory devices.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c         | 114 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  hw/ppc/spapr_drc.c     |  21 +++++++++
>  include/hw/ppc/spapr.h |   2 +
>  3 files changed, 136 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 06d000d..441012d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2110,6 +2110,109 @@ out:
>      error_propagate(errp, local_err);
>  }
> 
> +typedef struct sPAPRDIMMState {
> +    uint32_t nr_lmbs;
> +} sPAPRDIMMState;
> +
> +/*
> + * Called from spapr_drc.c: set_isolation_state().
> + *
> + * If the drc is being marked as ISOLATED, ensure that the corresponding
> + * LMB is part of the DIMM device which is being deleted.
> + */
> +int spapr_lmb_in_removable_dimm(sPAPRDRConnector *drc,
> +                                sPAPRDRIsolationState state)
> +{
> +    DeviceState *dev = drc->dev;
> +    PCDIMMDevice *dimm = PC_DIMM(dev);
> +
> +    if (state != SPAPR_DR_ISOLATION_STATE_ISOLATED) {
> +        return 0;
> +    }
> +
> +    if (!dimm->delete_pending) {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +static void spapr_lmb_release(DeviceState *dev, void *opaque)
> +{
> +    sPAPRDIMMState *ds = (sPAPRDIMMState *)opaque;
> +    HotplugHandler *hotplug_ctrl = NULL;
> +    Error *local_err = 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, &local_err);
> +}
> +
> +static void spapr_del_lmbs(DeviceState *dev, uint64_t addr, uint64_t size,
> +                           Error **errp)
> +{
> +    sPAPRDRConnector *drc;
> +    sPAPRDRConnectorClass *drck;
> +    uint32_t nr_lmbs = size/SPAPR_MEMORY_BLOCK_SIZE;
> +    Error *local_err = NULL;
> +    int i;
> +    sPAPRDIMMState *ds = g_malloc0(sizeof(sPAPRDIMMState));
> +
> +    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, &local_err);
> +        addr += SPAPR_MEMORY_BLOCK_SIZE;
> +    }
> +    spapr_hotplug_req_remove_by_count(SPAPR_DR_CONNECTOR_TYPE_LMB, nr_lmbs);
> +}
> +
> +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));
> +}

In the current code the unplug() and request_unplug() are mutually
exclusive. Are the plans on making the unplug() do something in the
prescence of request_unplug()? If so, I'd imagine it would've be a
forced removal, except maybe as a fallback if the request is determined
to fail somehow?

> +
> +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;
> +    }
> +
> +    dimm->delete_pending = true;
> +    spapr_del_lmbs(dev, addr, size, &local_err);
> +out:
> +    error_propagate(errp, local_err);
> +}
> +
>  static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>                                        DeviceState *dev, Error **errp)
>  {
> @@ -2157,7 +2260,15 @@ static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev,
>                                        DeviceState *dev, Error **errp)
>  {
>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> -        error_setg(errp, "Memory hot unplug not supported by sPAPR");
> +        spapr_memory_unplug(hotplug_dev, dev, errp);
> +    }
> +}
> +
> +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);
>      }
>  }
> 
> @@ -2191,6 +2302,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      mc->get_hotplug_handler = spapr_get_hotpug_handler;
>      hc->plug = spapr_machine_device_plug;
>      hc->unplug = spapr_machine_device_unplug;
> +    hc->unplug_request = spapr_machine_device_unplug_request;
> 
>      smc->dr_lmb_enabled = false;
>      fwc->get_dev_path = spapr_get_fw_dev_path;
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 8cbcf4d..b9d7c71 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -11,6 +11,7 @@
>   */
> 
>  #include "hw/ppc/spapr_drc.h"
> +#include "hw/ppc/spapr.h"
>  #include "qom/object.h"
>  #include "hw/qdev.h"
>  #include "qapi/visitor.h"
> @@ -63,9 +64,29 @@ static int set_isolation_state(sPAPRDRConnector *drc,
>                                 sPAPRDRIsolationState state)
>  {
>      sPAPRDRConnectorClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> +    int ret;
> 
>      DPRINTFN("drc: %x, set_isolation_state: %x", get_index(drc), state);
> 
> +    /*
> +     * Fail any requests to ISOLATE the LMB DRC if this LMB doesn't
> +     * belong to a DIMM device that is marked for removal.
> +     *
> +     * Currently the guest userspace tool drmgr that drives the memory
> +     * hotplug/unplug will just try to remove a set of 'removable' LMBs
> +     * in response to a hot unplug request that is based on drc-count.
> +     * If the LMB being removed doesn't belong to a DIMM device that is
> +     * actually being unplugged, fail the isolation request here.
> +     *
> +     * TODO: Calling out from spapr_drc.c like this doesn't look good.
> +     */
> +    if (drc->type == SPAPR_DR_CONNECTOR_TYPE_LMB) {
> +        ret = spapr_lmb_in_removable_dimm(drc, state);
> +        if (ret) {
> +            return RTAS_OUT_HW_ERROR;
> +        }
> +    }
> +
>      drc->isolation_state = state;
> 
>      if (drc->isolation_state == SPAPR_DR_ISOLATION_STATE_ISOLATED) {
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index d87c6d4..2039ca1 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -594,6 +594,8 @@ void spapr_hotplug_req_add_by_count(sPAPRDRConnectorType drc_type,
>                                         uint32_t count);
>  void spapr_hotplug_req_remove_by_count(sPAPRDRConnectorType drc_type,
>                                            uint32_t count);
> +int spapr_lmb_in_removable_dimm(sPAPRDRConnector *drc,
> +                                sPAPRDRIsolationState state);
> 
>  /* rtas-configure-connector state */
>  struct sPAPRConfigureConnectorState {
> -- 
> 2.1.0
>