pc-dimm: introduce get_vmstate_memory_region callback

This callback returns the MemoryRegion that is the memory of dimm should
be kept during live migration

nvdimm device is different with pc-dimm as its memory includes not only
the MemoryRegion directly mapping to guest's address space but also the
memory used as label data
Signed-off-by: NXiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/mem/pc-dimm.c

@@ -40,6 +40,8 @@ void pc_dimm_memory_plug(DeviceState *dev, MemoryHotplugState *hpms,
     int slot;
     MachineState *machine = MACHINE(qdev_get_machine());
     PCDIMMDevice *dimm = PC_DIMM(dev);
+    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
+    MemoryRegion *vmstate_mr = ddc->get_vmstate_memory_region(dimm);
     Error *local_err = NULL;
     uint64_t existing_dimms_capacity = 0;
     uint64_t addr;
@@ -105,7 +107,7 @@ void pc_dimm_memory_plug(DeviceState *dev, MemoryHotplugState *hpms,
     }
 
     memory_region_add_subregion(&hpms->mr, addr - hpms->base, mr);
-    vmstate_register_ram(mr, dev);
+    vmstate_register_ram(vmstate_mr, dev);
     numa_set_mem_node_id(addr, memory_region_size(mr), dimm->node);
 
 out:
@@ -116,10 +118,12 @@ void pc_dimm_memory_unplug(DeviceState *dev, MemoryHotplugState *hpms,
                            MemoryRegion *mr)
 {
     PCDIMMDevice *dimm = PC_DIMM(dev);
+    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
+    MemoryRegion *vmstate_mr = ddc->get_vmstate_memory_region(dimm);
 
     numa_unset_mem_node_id(dimm->addr, memory_region_size(mr), dimm->node);
     memory_region_del_subregion(&hpms->mr, mr);
-    vmstate_unregister_ram(mr, dev);
+    vmstate_unregister_ram(vmstate_mr, dev);
 }
 
 static int pc_existing_dimms_capacity_internal(Object *obj, void *opaque)
@@ -424,6 +428,11 @@ static MemoryRegion *pc_dimm_get_memory_region(PCDIMMDevice *dimm)
     return host_memory_backend_get_memory(dimm->hostmem, &error_abort);
 }
 
+static MemoryRegion *pc_dimm_get_vmstate_memory_region(PCDIMMDevice *dimm)
+{
+    return host_memory_backend_get_memory(dimm->hostmem, &error_abort);
+}
+
 static void pc_dimm_class_init(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
@@ -434,6 +443,7 @@ static void pc_dimm_class_init(ObjectClass *oc, void *data)
     dc->desc = "DIMM memory module";
 
     ddc->get_memory_region = pc_dimm_get_memory_region;
+    ddc->get_vmstate_memory_region = pc_dimm_get_vmstate_memory_region;
 }
 
 static TypeInfo pc_dimm_info = {

include/hw/mem/pc-dimm.h

@@ -61,7 +61,9 @@ typedef struct PCDIMMDevice {
  * @realize: called after common dimm is realized so that the dimm based
  * devices get the chance to do specified operations.
  * @get_memory_region: returns #MemoryRegion associated with @dimm which
- * is directly mapped into the physical address space of guest
+ * is directly mapped into the physical address space of guest.
+ * @get_vmstate_memory_region: returns #MemoryRegion which indicates the
+ * memory of @dimm should be kept during live migration.
  */
 typedef struct PCDIMMDeviceClass {
     /* private */
@@ -70,6 +72,7 @@ typedef struct PCDIMMDeviceClass {
     /* public */
     void (*realize)(PCDIMMDevice *dimm, Error **errp);
     MemoryRegion *(*get_memory_region)(PCDIMMDevice *dimm);
+    MemoryRegion *(*get_vmstate_memory_region)(PCDIMMDevice *dimm);
 } PCDIMMDeviceClass;
 
 /**