smbios: error out when building type 4 table is not possible

If SMBIOS v2 version is requested but number of cores/threads
are more than it's possible to describe with v2, error out
instead of silently ignoring the fact and filling core/thread
count with bogus values.

This will help caller to decide if it should fallback to
SMBIOSv3 when smbios-entry-point-type='auto'

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Ani Sinha <anisinha@redhat.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Message-Id: <20240314152302.2324164-18-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/smbios/smbios.c

@@ -669,7 +669,8 @@ static void smbios_build_type_3_table(void)
 }
 
 static void smbios_build_type_4_table(MachineState *ms, unsigned instance,
-                                      SmbiosEntryPointType ep_type)
+                                      SmbiosEntryPointType ep_type,
+                                      Error **errp)
 {
     char sock_str[128];
     size_t tbl_len = SMBIOS_TYPE_4_LEN_V28;
@@ -723,6 +724,12 @@ static void smbios_build_type_4_table(MachineState *ms, unsigned instance,
     if (tbl_len == SMBIOS_TYPE_4_LEN_V30) {
         t->core_count2 = t->core_enabled2 = cpu_to_le16(cores_per_socket);
         t->thread_count2 = cpu_to_le16(threads_per_socket);
+    } else if (t->core_count == 0xFF || t->thread_count == 0xFF) {
+        error_setg(errp, "SMBIOS 2.0 doesn't support number of processor "
+                         "cores/threads more than 255, use "
+                         "-machine smbios-entry-point-type=64 option to enable "
+                         "SMBIOS 3.0 support");
+        return;
     }
 
     SMBIOS_BUILD_TABLE_POST;
@@ -1111,7 +1118,10 @@ static bool smbios_get_tables_ep(MachineState *ms,
     assert(ms->smp.sockets >= 1);
 
     for (i = 0; i < ms->smp.sockets; i++) {
-        smbios_build_type_4_table(ms, i, ep_type);
+        smbios_build_type_4_table(ms, i, ep_type, errp);
+        if (*errp) {
+            goto err_exit;
+        }
     }
 
     smbios_build_type_8_table();