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>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/boards.h |  4 ++++
 hw/core/machine.c   | 27 +++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/hw/boards.h b/include/hw/boards.h
index 02f43ac5d4d..be0c0f04804 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 >*/
@@ -306,6 +309,7 @@ struct MachineClass {
     bool ignore_memory_transaction_failures;
     int numa_mem_align_shift;
     const char * const *valid_cpu_types;
+    GSList *(*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 f52a4f2273b..8b40735ef98 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1581,6 +1581,33 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
             return false;
         }
     }
+    if (mc->get_valid_cpu_types) {
+        GSList *vct = mc->get_valid_cpu_types(machine);
+        bool valid = false;
+        unsigned count = 0;
+        GSList *l;
+
+        for (l = vct; !valid && l != NULL; l = l->next) {
+            valid |= !!object_class_dynamic_cast(oc, l->data);
+            count++;
+        }
+
+        if (!valid) {
+            g_autofree char *requested = cpu_model_from_type(machine->cpu_type);
+            vct = g_slist_reverse(vct);
+            error_setg(errp, "Invalid CPU model: %s", requested);
+            error_append_hint(errp, "The valid models are: ");
+            for (l = vct; l != NULL; l = l->next) {
+                g_autofree char *model = cpu_model_from_type(l->data);
+                error_append_hint(errp, "%s%s", model, --count ? ", " : "");
+            }
+            error_append_hint(errp, "\n");
+        }
+        g_slist_free_full(vct, g_free);
+        if (!valid) {
+            return false;
+        }
+    }
 
     /* Check if CPU type is deprecated and warn if so */
     cc = CPU_CLASS(oc);
-- 
2.47.1

On 4/22/25 07:54, Philippe Mathieu-Daudé wrote:
> index f52a4f2273b..8b40735ef98 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -1581,6 +1581,33 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
>               return false;
>           }
>       }
> +    if (mc->get_valid_cpu_types) {
> +        GSList *vct = mc->get_valid_cpu_types(machine);
> +        bool valid = false;
> +        unsigned count = 0;
> +        GSList *l;
> +
> +        for (l = vct; !valid && l != NULL; l = l->next) {
> +            valid |= !!object_class_dynamic_cast(oc, l->data);
> +            count++;
> +        }
> +
> +        if (!valid) {
> +            g_autofree char *requested = cpu_model_from_type(machine->cpu_type);
> +            vct = g_slist_reverse(vct);
> +            error_setg(errp, "Invalid CPU model: %s", requested);
> +            error_append_hint(errp, "The valid models are: ");
> +            for (l = vct; l != NULL; l = l->next) {
> +                g_autofree char *model = cpu_model_from_type(l->data);
> +                error_append_hint(errp, "%s%s", model, --count ? ", " : "");
> +            }
> +            error_append_hint(errp, "\n");
> +        }
> +        g_slist_free_full(vct, g_free);
> +        if (!valid) {
> +            return false;
> +        }
> +    }

Why use GSList instead of GPtrArray?
That would provide you the count without manually computing it,
and it would avoid the need for any sort of reverse.
I think it would also allow you to auto-free the set.


r~

On 4/22/25 10:54, Richard Henderson wrote:
> On 4/22/25 07:54, Philippe Mathieu-Daudé wrote:
>> index f52a4f2273b..8b40735ef98 100644
>> --- a/hw/core/machine.c
>> +++ b/hw/core/machine.c
>> @@ -1581,6 +1581,33 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
>>                return false;
>>            }
>>        }
>> +    if (mc->get_valid_cpu_types) {
>> +        GSList *vct = mc->get_valid_cpu_types(machine);
>> +        bool valid = false;
>> +        unsigned count = 0;
>> +        GSList *l;
>> +
>> +        for (l = vct; !valid && l != NULL; l = l->next) {
>> +            valid |= !!object_class_dynamic_cast(oc, l->data);
>> +            count++;
>> +        }
>> +
>> +        if (!valid) {
>> +            g_autofree char *requested = cpu_model_from_type(machine->cpu_type);
>> +            vct = g_slist_reverse(vct);
>> +            error_setg(errp, "Invalid CPU model: %s", requested);
>> +            error_append_hint(errp, "The valid models are: ");
>> +            for (l = vct; l != NULL; l = l->next) {
>> +                g_autofree char *model = cpu_model_from_type(l->data);
>> +                error_append_hint(errp, "%s%s", model, --count ? ", " : "");
>> +            }
>> +            error_append_hint(errp, "\n");
>> +        }
>> +        g_slist_free_full(vct, g_free);
>> +        if (!valid) {
>> +            return false;
>> +        }
>> +    }
> 
> Why use GSList instead of GPtrArray?
> That would provide you the count without manually computing it,
> and it would avoid the need for any sort of reverse.
> I think it would also allow you to auto-free the set.
> 

Same remark than Richard, it would remove all the checks needed, as we 
can simply use this array "blindly".

> 
> r~