[Qemu-devel] [PATCH v3] hw/i386: Deprecate the machine types pc-0.10 and pc-0.11

[Thomas Huth <thuth@redhat.com>]

The oldest machine type which is still used in a still maintained distro
is a pc-0.12 based machine type in RHEL6, so everything that is older
than pc-0.12 should not be used anymore. Thus let's deprecate pc-0.10
and pc-0.11 so that we can finally remove them in a future release.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 This is based on a patch that I already sent in 2017. But back then, we
 were still in progress of discussing our deprecation policies (e.g. auto-
 matic deprecation for old machine types), and there was no clear consensus
 whether we should deprecate 0.10 - 0.11, all 0.x or even up to version 1.2.
 After some iterations and too much discussion, I've forgotten about this
 patch. Anyway, I think we agreed that at least 0.10 and 0.11 can certainly
 be removed nowadays, so let's finally get at least those two machine types
 marked as deprecated! If that works fine and we will finally have removed
 these two types in v3.2, we can resume the discussion about newer machine
 types afterwards.

 Note: I don't want to add a QMP interface for this in this patch here,
 let's keep this small and simple! If we decide that we need a QMP interface,
 we can do that with a separate patch later.

 v3:
 - Do not print the deprecation messages if qtest_enabled()

 v2:
 - Renamed deprecation_msg to deprecation_reason
 - Added information about that field to the MachineClass comment

 hw/i386/pc_piix.c   |  2 ++
 include/hw/boards.h |  4 ++++
 qemu-doc.texi       |  5 +++++
 vl.c                | 10 ++++++++--
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index e9b6f06..b4fd164 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -956,6 +956,8 @@ static void pc_i440fx_0_11_machine_options(MachineClass *m)
 {
     pc_i440fx_0_12_machine_options(m);
     m->hw_version = "0.11";
+    m->deprecation_reason = "Old and unsupported machine version, "
+                            "use a newer machine type instead.";
     SET_MACHINE_COMPAT(m, PC_COMPAT_0_11);
 }
 
diff --git a/include/hw/boards.h b/include/hw/boards.h
index ef7457f..6926928 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -107,6 +107,9 @@ typedef struct {
 
 /**
  * MachineClass:
+ * @deprecation_reason: If set, the machine is marked as deprecated. The
+ *    string should give some information about why the machine is deprecated,
+ *    and must provide some clear information about what to use instead.
  * @max_cpus: maximum number of CPUs supported. Default: 1
  * @min_cpus: minimum number of CPUs supported. Default: 1
  * @default_cpus: number of CPUs instantiated if none are specified. Default: 1
@@ -166,6 +169,7 @@ struct MachineClass {
     char *name;
     const char *alias;
     const char *desc;
+    const char *deprecation_reason;
 
     void (*init)(MachineState *state);
     void (*reset)(void);
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 282bc3d..16fcb47 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -2943,6 +2943,11 @@ support page sizes < 4096 any longer.
 
 @section System emulator machines
 
+@subsection pc-0.10 and pc-0.11 (since 3.0)
+
+These machine types are very old and likely can not be used for live migration
+from old QEMU versions anymore. A newer machine type should be used instead.
+
 @section Device options
 
 @subsection Block device options
diff --git a/vl.c b/vl.c
index b3426e0..6d54bc6 100644
--- a/vl.c
+++ b/vl.c
@@ -2560,8 +2560,9 @@ static gint machine_class_cmp(gconstpointer a, gconstpointer b)
             if (mc->alias) {
                 printf("%-20s %s (alias of %s)\n", mc->alias, mc->desc, mc->name);
             }
-            printf("%-20s %s%s\n", mc->name, mc->desc,
-                   mc->is_default ? " (default)" : "");
+            printf("%-20s %s%s%s\n", mc->name, mc->desc,
+                   mc->is_default ? " (default)" : "",
+                   mc->deprecation_reason ? " (deprecated)" : "");
         }
     }
 
@@ -4257,6 +4258,11 @@ int main(int argc, char **argv, char **envp)
 
     configure_accelerator(current_machine);
 
+    if (!qtest_enabled() && machine_class->deprecation_reason) {
+        error_report("Machine type '%s' is deprecated: %s",
+                     machine_class->name, machine_class->deprecation_reason);
+    }
+
     /*
      * Register all the global properties, including accel properties,
      * machine properties, and user-specified ones.
-- 
1.8.3.1