pc-dimm: add busy slot check and slot auto-allocation

- if slot property is not specified on -device/device_add command,
treat default value as request for assigning PCDIMMDevice to
the first free slot.

- if slot is provided with -device/device_add command, attempt to
use it or fail command if it's already occupied.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

3 files changed, 69 insertions, 0 deletions

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 4dc86d5..be5e3bb 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1547,8 +1547,10 @@ void qemu_register_pc_machine(QEMUMachine *m)
 static void pc_dimm_plug(HotplugHandler *hotplug_dev,
                          DeviceState *dev, Error **errp)
 {
+    int slot;
     Error *local_err = NULL;
     PCMachineState *pcms = PC_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);
@@ -1565,7 +1567,26 @@ static void pc_dimm_plug(HotplugHandler *hotplug_dev,
     if (local_err) {
         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;
+    }
 
     memory_region_add_subregion(&pcms->hotplug_memory,
                                 addr - pcms->hotplug_memory_base, mr);
diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
index 40b51c8..8c26568 100644
--- a/hw/mem/pc-dimm.c
+++ b/hw/mem/pc-dimm.c
@@ -23,6 +23,52 @@
 #include "qapi/visitor.h"
 #include "qemu/range.h"
 
+static int pc_dimm_slot2bitmap(Object *obj, void *opaque)
+{
+    unsigned long *bitmap = opaque;
+
+    if (object_dynamic_cast(obj, TYPE_PC_DIMM)) {
+        DeviceState *dev = DEVICE(obj);
+        if (dev->realized) { /* count only realized DIMMs */
+            PCDIMMDevice *d = PC_DIMM(obj);
+            set_bit(d->slot, bitmap);
+        }
+    }
+
+    object_child_foreach(obj, pc_dimm_slot2bitmap, opaque);
+    return 0;
+}
+
+int pc_dimm_get_free_slot(const int *hint, int max_slots, Error **errp)
+{
+    unsigned long *bitmap = bitmap_new(max_slots);
+    int slot = 0;
+
+    object_child_foreach(qdev_get_machine(), pc_dimm_slot2bitmap, bitmap);
+
+    /* check if requested slot is not occupied */
+    if (hint) {
+        if (*hint >= max_slots) {
+            error_setg(errp, "invalid slot# %d, should be less than %d",
+                       *hint, max_slots);
+        } else if (!test_bit(*hint, bitmap)) {
+            slot = *hint;
+        } else {
+            error_setg(errp, "slot %d is busy", *hint);
+        }
+        goto out;
+    }
+
+    /* search for free slot */
+    slot = find_first_zero_bit(bitmap, max_slots);
+    if (slot == max_slots) {
+        error_setg(errp, "no free slots available");
+    }
+out:
+    g_free(bitmap);
+    return slot;
+}
+
 static gint pc_dimm_addr_sort(gconstpointer a, gconstpointer b)
 {
     PCDIMMDevice *x = PC_DIMM(a);
diff --git a/include/hw/mem/pc-dimm.h b/include/hw/mem/pc-dimm.h
index 5a3e7df..0f4a6ba 100644
--- a/include/hw/mem/pc-dimm.h
+++ b/include/hw/mem/pc-dimm.h
@@ -74,4 +74,6 @@ uint64_t pc_dimm_get_free_addr(uint64_t address_space_start,
                                uint64_t address_space_size,
                                uint64_t *hint, uint64_t size,
                                Error **errp);
+
+int pc_dimm_get_free_slot(const int *hint, int max_slots, Error **errp);
 #endif