cpu: Assert DeviceClass::vmsd is NULL on user emulation

Migration is specific to system emulation.

Restrict current DeviceClass::vmsd to sysemu using #ifdef'ry,
and assert in cpu_exec_realizefn() that dc->vmsd not set under
user emulation.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210517105140.1062037-12-f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

cpu.c

@@ -141,6 +141,8 @@ void cpu_exec_realizefn(CPUState *cpu, Error **errp)
 #endif /* CONFIG_TCG */
 
 #ifdef CONFIG_USER_ONLY
+    assert(qdev_get_vmsd(DEVICE(cpu)) == NULL ||
+           qdev_get_vmsd(DEVICE(cpu))->unmigratable);
     assert(cc->vmsd == NULL);
 #else
     if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {

target/sh4/cpu.c

@@ -218,10 +218,12 @@ static void superh_cpu_initfn(Object *obj)
     env->movcal_backup_tail = &(env->movcal_backup);
 }
 
+#ifndef CONFIG_USER_ONLY
 static const VMStateDescription vmstate_sh_cpu = {
     .name = "cpu",
     .unmigratable = 1,
 };
+#endif
 
 #include "hw/core/tcg-cpu-ops.h"
 
@@ -257,12 +259,11 @@ static void superh_cpu_class_init(ObjectClass *oc, void *data)
     cc->gdb_write_register = superh_cpu_gdb_write_register;
 #ifndef CONFIG_USER_ONLY
     cc->get_phys_page_debug = superh_cpu_get_phys_page_debug;
+    dc->vmsd = &vmstate_sh_cpu;
 #endif
     cc->disas_set_info = superh_cpu_disas_set_info;
 
     cc->gdb_num_core_regs = 59;
-
-    dc->vmsd = &vmstate_sh_cpu;
     cc->tcg_ops = &superh_tcg_ops;
 }
 

target/xtensa/cpu.c

@@ -175,10 +175,12 @@ static void xtensa_cpu_initfn(Object *obj)
 #endif
 }
 
+#ifndef CONFIG_USER_ONLY
 static const VMStateDescription vmstate_xtensa_cpu = {
     .name = "cpu",
     .unmigratable = 1,
 };
+#endif
 
 #include "hw/core/tcg-cpu-ops.h"
 
@@ -215,9 +217,9 @@ static void xtensa_cpu_class_init(ObjectClass *oc, void *data)
     cc->gdb_stop_before_watchpoint = true;
 #ifndef CONFIG_USER_ONLY
     cc->get_phys_page_debug = xtensa_cpu_get_phys_page_debug;
+    dc->vmsd = &vmstate_xtensa_cpu;
 #endif
     cc->disas_set_info = xtensa_cpu_disas_set_info;
-    dc->vmsd = &vmstate_xtensa_cpu;
     cc->tcg_ops = &xtensa_tcg_ops;
 }