Add MachineClass::get_valid_cpu_types(), a helper that
returns a dynamic list of CPU types. Since the helper
takes a MachineState argument, we know the machine is
created by the time we call it.

Suggested-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/boards.h |  4 ++++
 hw/core/machine.c   | 28 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/hw/boards.h b/include/hw/boards.h
index a60e1d83390..8fc34579412 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -259,6 +259,9 @@ typedef struct {
  * @smbios_memory_device_size:
  *    Default size of memory device,
  *    SMBIOS 3.1.0 "7.18 Memory Device (Type 17)"
+ * @get_valid_cpu_types:
+ *    Returns a list of valid CPU types for this board. May be NULL
+ *    if not needed.
  */
 struct MachineClass {
     /*< private >*/
@@ -305,6 +308,7 @@ struct MachineClass {
     bool ignore_memory_transaction_failures;
     int numa_mem_align_shift;
     const char * const *valid_cpu_types;
+    GPtrArray *(*get_valid_cpu_types)(const MachineState *ms);
     strList *allowed_dynamic_sysbus_devices;
     bool auto_enable_numa_with_memhp;
     bool auto_enable_numa_with_memdev;
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 681adbb7ac5..5d9684fbc85 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1573,6 +1573,8 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
      */
     if (mc->valid_cpu_types) {
         assert(mc->valid_cpu_types[0] != NULL);
+        assert(!mc->get_valid_cpu_types);
+
         for (i = 0; mc->valid_cpu_types[i]; i++) {
             if (object_class_dynamic_cast(oc, mc->valid_cpu_types[i])) {
                 break;
@@ -1599,6 +1601,32 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
                 error_append_hint(errp, "\n");
             }
 
+            return false;
+        }
+    } else if (mc->get_valid_cpu_types) {
+        GPtrArray *vct = mc->get_valid_cpu_types(machine);
+        bool valid = false;
+
+        for (i = 0; i < vct->len; i++) {
+            if (object_class_dynamic_cast(oc, vct->pdata[i])) {
+                valid = true;
+                break;
+            }
+        }
+
+        if (!valid) {
+            g_autofree char *requested = cpu_model_from_type(machine->cpu_type);
+
+            error_setg(errp, "Invalid CPU model: %s", requested);
+            error_append_hint(errp, "The valid models are: ");
+            for (i = 0; i < vct->len; i++) {
+                g_autofree char *model = cpu_model_from_type(vct->pdata[i]);
+                error_append_hint(errp, "%s%s",
+                                  model, i + 1 == vct->len ? "\n" : ", ");
+            }
+        }
+        g_ptr_array_free(vct, true);
+        if (!valid) {
             return false;
         }
     }
-- 
2.51.0