Re: [Qemu-devel] [RFC PATCH v1 13/13] spapr: Memory hotplug support

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jan 08, 2015 at 11:40:20AM +0530, Bharata B Rao wrote:
> Make use of pc-dimm infrastructure to support memory hotplug
> for PowerPC.
> 
> Modelled on i386 memory hotplug.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c        | 107 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  hw/ppc/spapr_events.c |   3 ++
>  2 files changed, 108 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6964b06..1ffff39 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -58,7 +58,8 @@
>  #include "hw/nmi.h"
>  
>  #include "hw/compat.h"
> -
> +#include "hw/mem/pc-dimm.h"
> +#include "qapi/qmp/qerror.h"
>  #include <libfdt.h>
>  
>  /* SLOF memory layout:
> @@ -2165,6 +2166,103 @@ static void spapr_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
>      return;
>  }
>  
> +static int spapr_dimms_capacity(Object *obj, void *opaque)
> +{
> +    Error *local_err = NULL;
> +    uint64_t *size = opaque;
> +
> +    if (object_dynamic_cast(obj, TYPE_PC_DIMM)) {
> +        (*size) += object_property_get_int(obj, PC_DIMM_SIZE_PROP, &local_err);
> +
> +        if (local_err) {
> +            qerror_report_err(local_err);
> +            error_free(local_err);
> +            return 1;
> +        }
> +    }
> +
> +    object_child_foreach(obj, spapr_dimms_capacity, opaque);
> +    return 0;
> +}

I don't see any reason you can't use pc_existing_dimms_capacity()
rather than duplicating it.

> +static void spapr_memory_plug(HotplugHandler *hotplug_dev,
> +                         DeviceState *dev, Error **errp)
> +{
> +    int slot;
> +    Error *local_err = NULL;
> +    sPAPRMachineState *ms = SPAPR_MACHINE(hotplug_dev);
> +    MachineState *machine = MACHINE(hotplug_dev);
> +    PCDIMMDevice *dimm = PC_DIMM(dev);
> +    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> +    MemoryRegion *mr = ddc->get_memory_region(dimm);
> +    uint64_t dimms_capacity = 0;
> +    uint64_t align = TARGET_PAGE_SIZE; /* TODO: enforce alignment */
> +    uint64_t addr;
> +    sPAPRDRConnector *drc;
> +
> +    addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    addr = pc_dimm_get_free_addr(ms->hotplug_memory_base,
> +                                 memory_region_size(&ms->hotplug_memory),
> +                                 !addr ? NULL : &addr, align,
> +                                 memory_region_size(mr), &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    if (spapr_dimms_capacity(OBJECT(machine), &dimms_capacity)) {
> +        error_setg(&local_err, "failed to get total size of existing DIMMs");
> +        goto out;
> +    }
> +
> +    if (dimms_capacity > machine->maxram_size - machine->ram_size) {
> +        error_setg(&local_err, "not enough space, proposed use of 0x%" PRIx64
> +                   " from total of 0x" RAM_ADDR_FMT,
> +                   dimms_capacity, machine->maxram_size);
> +        goto out;
> +    }
> +
> +    object_property_set_int(OBJECT(dev), addr, PC_DIMM_ADDR_PROP, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    slot = pc_dimm_get_free_slot(slot == PC_DIMM_UNASSIGNED_SLOT ? NULL : &slot,
> +                                 machine->ram_slots, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +    object_property_set_int(OBJECT(dev), slot, PC_DIMM_SLOT_PROP, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    if (kvm_enabled() && !kvm_has_free_slot(machine)) {
> +        error_setg(&local_err, "hypervisor has no free memory slots left");
> +        goto out;
> +    }
> +
> +    memory_region_add_subregion(&ms->hotplug_memory,
> +                                addr - ms->hotplug_memory_base, mr);
> +    vmstate_register_ram(mr, dev);
> +
> +    drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
> +            addr/SPAPR_MIN_MEMORY_BLOCK_SIZE);
> +    g_assert(drc);
> +    spapr_hotplug_req_add_event(drc);
> +
> +out:
> +    error_propagate(errp, local_err);
> +}

It looks like this is basically the same as pc_dimm_plug() except for
a couple of checks and the last section which actually notifies the
guest.  Could this be made into common code in pc-dimm.c with hooks
for the platform specific notification?

Maybe PC and sPAPR subclasses of a common dimm object?

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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