cpu: Introduce CPU model deprecation API

Implement the ability of marking some versions deprecated. When
that CPU model is chosen, print a warning.  The warning message
can be customized, e.g. suggesting an alternative CPU model to be
used instead.

The deprecation message will be printed by x86_cpu_list_entry(),
e.g. '-cpu help'.

QMP command 'query-cpu-definitions' will return a bool value
indicating the deprecation status.

Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
Message-Id: <1600758855-80046-1-git-send-email-robert.hu@linux.intel.com>
[ehabkost: reword commit message]
[ehabkost: Handle NULL cpu_type]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

4 files changed, 27 insertions, 3 deletions

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 7e2f4ec08e..d740a7e963 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1087,6 +1087,8 @@ MemoryRegion *machine_consume_memdev(MachineState *machine,
 void machine_run_board_init(MachineState *machine)
 {
     MachineClass *machine_class = MACHINE_GET_CLASS(machine);
+    ObjectClass *oc = object_class_by_name(machine->cpu_type);
+    CPUClass *cc;
 
     if (machine->ram_memdev_id) {
         Object *o;
@@ -1106,11 +1108,10 @@ void machine_run_board_init(MachineState *machine)
      * specified a CPU with -cpu check here that the user CPU is supported.
      */
     if (machine_class->valid_cpu_types && machine->cpu_type) {
-        ObjectClass *class = object_class_by_name(machine->cpu_type);
         int i;
 
         for (i = 0; machine_class->valid_cpu_types[i]; i++) {
-            if (object_class_dynamic_cast(class,
+            if (object_class_dynamic_cast(oc,
                                           machine_class->valid_cpu_types[i])) {
                 /* The user specificed CPU is in the valid field, we are
                  * good to go.
@@ -1133,6 +1134,13 @@ void machine_run_board_init(MachineState *machine)
         }
     }
 
+    /* Check if CPU type is deprecated and warn if so */
+    cc = CPU_CLASS(oc);
+    if (cc && cc->deprecation_note) {
+        warn_report("CPU model %s is deprecated -- %s", machine->cpu_type,
+                    cc->deprecation_note);
+    }
+
     machine_class->init(machine);
 }
 
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 4879f25026..9c3a45ad7b 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -155,6 +155,8 @@ struct TranslationBlock;
  * @disas_set_info: Setup architecture specific components of disassembly info
  * @adjust_watchpoint_address: Perform a target-specific adjustment to an
  * address before attempting to match it against watchpoints.
+ * @deprecation_note: If this CPUClass is deprecated, this field provides
+ *                    related information.
  *
  * Represents a CPU family or model.
  */
@@ -221,6 +223,7 @@ struct CPUClass {
     vaddr (*adjust_watchpoint_address)(CPUState *cpu, vaddr addr, int len);
     void (*tcg_initialize)(void);
 
+    const char *deprecation_note;
     /* Keep non-pointer data at the end to minimize holes.  */
     int gdb_num_core_regs;
     bool gdb_stop_before_watchpoint;
diff --git a/qapi/machine-target.json b/qapi/machine-target.json
index 698850cc78..fec3bb8679 100644
--- a/qapi/machine-target.json
+++ b/qapi/machine-target.json
@@ -286,6 +286,10 @@
 #            in the VM configuration, because aliases may stop being
 #            migration-safe in the future (since 4.1)
 #
+# @deprecated: If true, this CPU model is deprecated and may be removed in
+#              in some future version of QEMU according to the QEMU deprecation
+#              policy. (since 5.2)
+#
 # @unavailable-features is a list of QOM property names that
 # represent CPU model attributes that prevent the CPU from running.
 # If the QOM property is read-only, that means there's no known
@@ -310,7 +314,8 @@
             'static': 'bool',
             '*unavailable-features': [ 'str' ],
             'typename': 'str',
-            '*alias-of' : 'str' },
+            '*alias-of' : 'str',
+            'deprecated' : 'bool' },
   'if': 'defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_I386) || defined(TARGET_S390X) || defined(TARGET_MIPS)' }
 
 ##
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 25ec64124e..2e3ee41c56 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1633,6 +1633,7 @@ typedef struct X86CPUDefinition {
      * If NULL, version 1 will be registered automatically.
      */
     const X86CPUVersionDefinition *versions;
+    const char *deprecation_note;
 } X86CPUDefinition;
 
 /* Reference to a specific CPU model version */
@@ -4990,6 +4991,11 @@ static void x86_cpu_definition_entry(gpointer data, gpointer user_data)
     info->migration_safe = cc->migration_safe;
     info->has_migration_safe = true;
     info->q_static = cc->static_model;
+    if (cc->model && cc->model->cpudef->deprecation_note) {
+        info->deprecated = true;
+    } else {
+        info->deprecated = false;
+    }
     /*
      * Old machine types won't report aliases, so that alias translation
      * doesn't break compatibility with previous QEMU versions.
@@ -5380,9 +5386,11 @@ static void x86_cpu_cpudef_class_init(ObjectClass *oc, void *data)
 {
     X86CPUModel *model = data;
     X86CPUClass *xcc = X86_CPU_CLASS(oc);
+    CPUClass *cc = CPU_CLASS(oc);
 
     xcc->model = model;
     xcc->migration_safe = true;
+    cc->deprecation_note = model->cpudef->deprecation_note;
 }
 
 static void x86_register_cpu_model_type(const char *name, X86CPUModel *model)