pc: exit QEMU if number of slots more than supported 256

... which is imposed by current naming scheme of ACPI memory devices.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Acked-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/i386/pc.c

@@ -1230,6 +1230,12 @@ FWCfgState *pc_memory_init(MemoryRegion *system_memory,
         ram_addr_t hotplug_mem_size =
             machine->maxram_size - ram_size;
 
+        if (machine->ram_slots > ACPI_MAX_RAM_SLOTS) {
+            error_report("unsupported amount of memory slots: %"PRIu64,
+                         machine->ram_slots);
+            exit(EXIT_FAILURE);
+        }
+
         pcms->hotplug_memory_base =
             ROUND_UP(0x100000000ULL + above_4g_mem_size, 1ULL << 30);
 

include/hw/acpi/acpi.h

@@ -26,6 +26,12 @@
 #include "exec/memory.h"
 #include "hw/irq.h"
 
+/*
+ * current device naming scheme supports
+ * only upto 256 memory devices
+ */
+#define ACPI_MAX_RAM_SLOTS 256
+
 /* from linux include/acpi/actype.h */
 /* Default ACPI register widths */