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

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

On Tue, Feb 24, 2015 at 05:26:12PM +1100, David Gibson wrote:
> 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.

Already done that and got the required stuff pushed upstream.
http://lists.gnu.org/archive/html/qemu-devel/2015-01/msg03589.html

> 
> > +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?

Yes I could do that.

> 
> Maybe PC and sPAPR subclasses of a common dimm object?

Will take a look and see how best this can be done.

Regards,
Bharata.